Source: OKLAHOMA STATE UNIVERSITY submitted to NRP
STUDIES OF ALTERNATE BEARING IN PECAN
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
0090438
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Oct 1, 2003
Project End Date
Sep 30, 2014
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Recipient Organization
OKLAHOMA STATE UNIVERSITY
(N/A)
STILLWATER,OK 74078
Performing Department
Horticulture & Landscape Architecture
Non Technical Summary
Pecan is a major Oklahoma agricultural commodity with over 85,000 acres on 2,800 farms (USDA National Agricultural Statistical Service). Oklahoma's producers sell about 18,000,000 lbs. of pecans annually, ranking Oklahoma 4th in total production and second in native pecan production among the pecan producing states. Leaf nickel sufficiency guidelines Nickel has been recently recognized as an essential element (Association of American Plant Food Control Officials, 2005), with pecan being one of the crops particularly sensitive to Ni deficiency. No information exists relating the status of Ni nutrition in Oklahoma pecans, their response to applied Ni, and leaf sufficiency levels to guide fertility recommendations. Kernel necrosis One producer contacted numerous pecan scientists concerning a persistent problem with dark or black basal ends of kernels. Upon more extensive investigation, the problem was discovered at other locations, although not as prevalent as at the original orchard (Smith et al., 2007). The problem was linked to common ancestry of the affected cultivars. The high incidence of what we called kernel necrosis at the original producer's orchard appeared to be associated with excessive N from nitrate contaminated ground water. The current hypothesis is that excessive N results in a toxic concentration of urea or perhaps other reduced-N compounds accumulating in the liquid endosperm, causing damage to the testa, resulting in a blackened and poorly developed basal end of the cotyledon. Urease is responsible for urea metabolism to be either incorporated into amino acids or volatilized as NH3. Nickel, a urease cofactor, may be effective in mitigating kernel damage caused by excessive N by increasing urea metabolism. Ground cover management Ground cover management has a dramatic impact on pecan orchard establishment and initial tree growth rates (Smith et al., 2001, 2002, 2005a, 2005b). Little data is available concerning ground cover interactions with bearing trees. This project will continue plots that were began during establishment, and are now in its eighth year with trees in their 4th year of production.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
(N/A)
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
1021211101080%
2051211114020%
Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships; 205 - Plant Management Systems;

Subject Of Investigation
1211 - Pecan;

Field Of Science
1010 - Nutrition and metabolism; 1140 - Weed science;
Goals / Objectives
Determine response to foliar applied Ni, and leaf sufficiency concentrations to guide Ni fertilizer recommendations. Investigate interactions of Ni, copper (Cu) and N on the incidence of kernel necrosis (Smith et al., 2007). Continue evaluation of bermudagrass [Cynodon dactylon (L.) Pers.] (Smith et al., 2005) and tall fescue (Festuca arundinacae Shreb.) (Smith et al., 2002) ground covers in a bearing pecan orchard..
Project Methods
Nickle status of pecan orchards in the area suggests a shortage. The study will be conducted on Pawnee trees. Treatments will be a control and Ni treated using Nickel Plus at the manufacturer's recommended rate and a surfactant. Treatments will be applied three times beginning at the parachute stage of budbreak, and then twice more at two week intervals. Treatments will be replicated 12 times in a completely randomized design. Leaf elemental concentrations of selected elements will be determined in July using standard index tissue and protocols. Yield, nut quality parameters and tree growth will be measured annually. The experiment will continue for three to five years. The second study will be conducted in a Pawnee orchard that frequently exhibits kernel necrosis. Treatments will include a control, foliar CuSO4 at 2 lbs/acre, Nickel Plus at 1 pint/acre, and CuSO4 plus Nickel Plus plus ZnSO4. Treatments will be replicated 12 times in a completely randomized design. Treatments will be applied three times per year beginning during the parachute stage of budbreak, and then twice more at two week intervals. Dependent variables will include leaf Ni concentration following the first application, and selected leaf elemental concentrations in July using standard index tissue and procedures. The liquid endosperm will be collected and frozen in the field on dry ice, transported to the laboratory and analyzed for concentrations of selected reduced-N compounds. Tree yield will be measured annually, and nut quality parameters analyzed from duplicated 20-nut samples per tree. In addition, kernels will be graded for necrosis using established procedures. This study will continue for three to five years. This is a continuation of two studies that characterize tree response to selected vegetation-free areas surrounding the tree in fescue or bermudagrass sods (Smith et al., 2002, 2005b). The initial manuscripts reported response prior to bearing and is now evaluating response of bearing trees. In both studies circles 0, 0.91, 1.83, 3.66 or 7.32 m in diameter centered on the tree are maintained vegetation-free. Treatments are replicated 12 times in a randomized complete block design. Plots are managed using standard commercial practices, and are irrigated with solid set sprinklers. Vegetation-free areas and pure stands of either fescue or bermudagrass are maintained with appropriate herbicide intervention. Dependent variables include tree growth as indicated by annual trunk diameter measurements, yield, weight per nut, kernel percentage and leaf elemental concentration of selected essential elements.

Progress 10/01/03 to 09/30/14

Outputs
Target Audience: Pecan producers and processors in the U.S.A. and elsewhere; scientists and extension personnel working with pecans or those with interests related to the particular research project. Changes/Problems: No changes are planned, simply following the logical progression of information generated from earlier studies on the particular topic. What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? The results of each of these topics have been disseminated to scientists and extension personnel via refereed publications and presentations. In addition, each of these topics has been presented at several producer conferences with attendance ranging from 25 to over 300 individuals. In addition, some of these topics were covered at a field day in Georgia with over 400 individuals in attendance. What do you plan to do during the next reporting period to accomplish the goals? This is the final report for this project period. Several of the projects reported here have additional work planned.

Impacts
What was accomplished under these goals? The characteristics of “kernel necrosis” have been defined, cultivars identified that are susceptible to this malady and the geographic area where this occurs has been identified and expanded. Several possible causes of this problem have been eliminated by research. Other possible causes, particularly acute susceptibility of certain cultivars to arsenic toxicity, are being investigated. Research has demonstrated banding phosphorus and potassium over drip irrigation lines effectively increased uptake resulting in correcting shortages and improving nut quality and yields. Additional research is underway to refine application times to achieve the greatest return on investment. Research has demonstrated the relationship between selective removal of inferior pecan trees, remaining old trees and survival and growth of newly transplanted trees. A surprising result of this study was a strongly positive relationship between distance from the remaining stump and growth of the transplant. This study will continue to determine initial productivity of the young trees and then data will be subjected to economic analysis to provide producers needed information to guide decisions and secure needed loans. An unseasonable spring freeze allowed characterization of damage to certain pecan cultivars. Thus future recommendations will note the susceptibility to such damage. Two studies demonstrated the relationship between the size of the vegetation free area surrounding a pecan tree with yield over several years. Depending on the ground cover cumulative yield was doubled or tripled with a 7.3 m diameter vegetation free circle compared to only mowing vegetation. Cumulative results of studies conducted in this five year report and pervious reports allowed publication of a comprehensive manuscript relating essential element deficiency and sufficiency levels for pecan along with recommendations to correct deficiencies or maintain trees within sufficiency levels. Certain pecans with thin shells tend to split at the shell suture during the 1st harvest, but not during the 2nd harvest. Split sutures reduce nut value up to 80%. Research demonstrated split sutures were caused by high seed moisture content combined with high solar radiant exposure typical of a sunny day. By changing 1st harvest procedures to harvest cultivars without a tendency to split on sunny days and those that split on cloudy days suture split was nearly eliminated substantially reducing costs associated with cleaning and removing split sutures and increasing total crop value.

Publications

  • Type: Conference Papers and Presentations Status: Other Year Published: 2011 Citation: Smith, M.W. February 2011. Industry driven pecan research and extension priorities, SE Pecan Growers Assn., Biloxi, MS.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2011 Citation: Smith, M.W. June 2011. Benefits of correcting potassium and phosphorus shortages, Tri-state Pecan Conference, Shreveport, LA.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2011 Citation: Smith, M.W. July 2011. Benefits of correcting potassium and phosphorus shortages. Texas Pecan Growers Assn Annual Meeting, Frisco, TX.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2012 Citation: Smith, M.W. March 2012. Re-evaluation of potassium and phosphorus requirements. Western Pecan Growers Assn. Conf., Las Cruces, NM.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2012 Citation: Smith, M.W. Sept. 2012. Revised nutrient sufficiency ranges and fertilizer guidelines for pecan. Alabama Pecan Growers Assn. Meeting, Fairhope,.AL.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2012 Citation: Smith, M.W. Sept. 2012. Banding fertilizers in pecan orchards. Alabama Pecan Growers Assn. Meeting, Fairhope,.AL.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2013 Citation: Smith, M.W. 2013. Pecan sanitation. Arkansas Pecan Growers Assn., Aug. 24, 2013, Hope, AR.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Smith, M.W., W.D. Goff, and M.L. Wells. 2013. Pecan orchard renewal: influence of established trees and remaining stumps on transplant growth and crown gall infection. HortScience 48:720-723.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Smith, M.W. and B.S. Cheary. 2013. Response of pecan to annual soil band-applications of phosphorus and potassium. HortScience 48:1411-1415.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Tan, C., Y. Wu, C.M. Taliaferro, G.E. Bell, D.L. Martin, M. W. Smith, and J.Q. Moss. 2014. Selfing and outcrossing fertility in Cynodon dactylon (L.) Pers. var. dactylon under open-pollinating conditions examined by SSR markers. Crop Sci. 54:1832-1837. Doi:10.2135/cropsci2013.120816.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Tan, C.C. Y.Q. Wu, C.M. Taliaferro, G.E. Bell, D.L. Martin, and M.W. Smith. 2014. Development and characterization of genomic SSR markers in Cynodon transvaalensis Burtt-Davy. Mol. Genet. Genomics doi: 10.1007/s00438-014-0829-1.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Dobhal, S., G. Zhang, C. Rohla, M. W. Smith, and L.M. Ma. 2014. A simple, rapid, cost-effective and sensitive method for detection of Salmonella in environmental samples. J. Applied Microbiol. 1-10. doi: 10.1111/jam.12583.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Smith, M.W. and B.S. Cheary. 2014. Size of the vegetation-free area surrounding pecan trees in a tall fescue sod affects production. Sci. Hort. 172:206-209.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Smith, M.W. and W.D. Goff. 2014. Pecan nut suture splits are positively related to kernel moisture concentration and solar radiant exposure. HortTechnology 24:238-240.
  • Type: Journal Articles Status: Awaiting Publication Year Published: 2014 Citation: Dong, H., S. Lu-Thames, L. Liu, M.W. Smith, L. Yan, and Y. Wu. 2014. QTL mapping for reproductive maturity in lowland switchgrass populations. J. Theoretical Applied Genetics (in press).
  • Type: Journal Articles Status: Awaiting Publication Year Published: 2014 Citation: Smith, M.W. and W.D. Goff. 2014. Patch budding pecans: Girdling, tipping, age and size of budwood and rootstock for budding; girdling, 2,3,5-tridobenzoic acid (TIBA) and 6-benzylaminopurine (BAP) for bud forcing. HortTechnology (in press).
  • Type: Journal Articles Status: Awaiting Publication Year Published: 2014 Citation: Weckler, P., C. Jones, T. Bowser, J. Hardin, N. Wang, A. Franzen, S. Mathanker, N. Maness, and M. Smith. 2014. Technologies for enhancing pecan production and processing. Acta Hort. (in press).
  • Type: Theses/Dissertations Status: Published Year Published: 2010 Citation: Wagle, P. 2010. Foliar application of nickel and/or copper on pecan performance in container and the field. (M.S.)
  • Type: Theses/Dissertations Status: Published Year Published: 2012 Citation: Chaney, J.W. 2012. Performance evaluation of seedling pecan trees using commonly selected commercially available tree shelters and the effect of glyphosate application on pecan kernel necrosis. (M.S.)
  • Type: Other Status: Published Year Published: 2010 Citation: Smith, M.W. and P. Weckler. 2010. Pecan industry to establish research, extension priorities. Pecan South 43(10):12-14.
  • Type: Other Status: Published Year Published: 2010 Citation: Smith, M.W. 2010. Relationship of leaf necrosis and defoliation to phosphorus and potassium concentrations in selected tissue. Okla. Pecan Growers Assn. Newsletter 51(1):2-3.
  • Type: Other Status: Published Year Published: 2010 Citation: Wagle, P., M.W. Smith, B.W. Wood, C.R. Reilly, and C.R. Rohla. 2010. Foliar application of nickel and copper on pecan. Okla. Pecan Growers Assn. Newsletter 51(1): 3.
  • Type: Other Status: Published Year Published: 2010 Citation: Smith, M.W. 2010. Cold damage? Okla. Pecan Growers Newsletter 51(1): 5-6.
  • Type: Other Status: Published Year Published: 2010 Citation: Smith, M.W. and B.S. Cheary. 2010. Bud damage from the spring 2009 freeze. Okla. Pecan Growers Assn. Newsletter 51(2): 4-6.
  • Type: Other Status: Published Year Published: 2010 Citation: Smith, M.W. 2010. Leaf analysis standards for pecan  revised 2010. Okla. Pecan Growers Assn. Newsletter 51(3): 6.
  • Type: Other Status: Published Year Published: 2010 Citation: Wagle, P., M.W. Smith, B.W. Wood and C.T. Rohla. 2010. Supplemental foliar nickel and copper applications do not reduce kernel necrosis in pecan trees receiving excess nitrogen. Okla. Pecan Growers Assn. Newsletter 51(4): 1-2.
  • Type: Other Status: Published Year Published: 2010 Citation: Wagle, P., M.W. Smith, B.W. Wood, and C.T. Rohla. 2010. Response of young bearing pecan trees to spring foliar nickel applications. Okla. Pecan Growers Assn. Newsletter 51(4): 3.
  • Type: Other Status: Published Year Published: 2012 Citation: Smith, M.W. 2012. OSU pecan research and extension support. Okla. Pecan Growers Assn. Newsletter 53(1):2.
  • Type: Other Status: Published Year Published: 2010 Citation: Smith, M.W. 2010. Shaker pad lubrication. Okla. Pecan Growers Assn. Newsletter 51(4): 3-4.
  • Type: Other Status: Published Year Published: 2010 Citation: Smith, M.W. 2010. Pecan phenology. Okla. Pecan Growers Assn. Newsletter 51(4): 4.
  • Type: Other Status: Published Year Published: 2011 Citation: Smith, M.W. (ed.). 2011. Okla. Pecan Growers Assn Newsletter. vol. 52 (1, 2, 3, 4).
  • Type: Other Status: Published Year Published: 2011 Citation: Smith, M.W. 2011. Is university support going away? Okla. Pecan Growers Assn. Newsletter 52(4):2.
  • Type: Other Status: Published Year Published: 2011 Citation: Smith, M.W. 2011. 2011 growing season. Okla. Pecan Growers Assn. Newsletter 52(4): 3-5.
  • Type: Other Status: Published Year Published: 2011 Citation: Smith, M.W. 2011. Pecan production in 2011. Okla. Pecan Growers Assn. Newsletter 52(3):12-14.
  • Type: Other Status: Published Year Published: 2011 Citation: Smith, M.W. 2011. Oklahomas weather. Okla. Pecan Growers Assn. Newsletter 52(2):7-8.
  • Type: Other Status: Published Year Published: 2011 Citation: Smith, M.W. 2011. The 2010 growing season. Okla. Pecan Growers Assn. Newsletter 52(1):2-3.
  • Type: Other Status: Published Year Published: 2012 Citation: Smith, M.W. 2012. Correcting phosphorus and potassium shortages. Okla. Pecan Growers Assn. Newsletter 53(1):5-8.
  • Type: Other Status: Published Year Published: 2012 Citation: Smith, M.W. 2012. 2012 season update. Okla. Pecan Growers Assn. Newsletter 53(2):1-2.
  • Type: Other Status: Published Year Published: 2012 Citation: Smith, M.W. 2012. Pecan cultivars. Okla. Pecan Growers Assn. Newsletter 53(4):2-4.
  • Type: Other Status: Published Year Published: 2012 Citation: Smith, M.W. 2012. Pecan kernel necrosis. Okla. Pecan Growers Assn. Newsletter 53(3):2.
  • Type: Other Status: Published Year Published: 2012 Citation: Smith, M.W. 2012. Do you need extension? Okla. Pecan Growers Assn. Newsletter 53(4):5.
  • Type: Other Status: Published Year Published: 2012 Citation: Smith, M.W. (ed.). 2012. Oklahoma Pecan Growers Assn. Newsletter, vol. 1-4.
  • Type: Other Status: Published Year Published: 2013 Citation: Smith, M.W., C.T. Rohla, and W.D. Goff. 2013. Pecan leaf elemental sufficiency ranges and fertilizer recommendations. Pecan Grower 24(3):50-63.
  • Type: Other Status: Published Year Published: 2013 Citation: Smith, M.W. 2013. 2012 Growing season. Oklahoma Pecan Growers Newsletter. 54(1):1-3.
  • Type: Other Status: Published Year Published: 2013 Citation: Smith, M.W., W. D. Goff, and M.L. Wells. 2013. Pecan orchard renewal: Influence of established trees and remaining stumps on transplant growth and crown gall infection. Pecan Grower 25(2)20-28.
  • Type: Other Status: Published Year Published: 2013 Citation: Smith, M.W. 2013. Georgias pecan field day. Oklahoma Pecan Growers Newsletter 54(4):3-6.
  • Type: Other Status: Published Year Published: 2013 Citation: Smith, M.W. 2013. Notes on the 2013 pecan crop. Oklahoma Pecan Growers Newsletter 54(3):6-7.
  • Type: Other Status: Published Year Published: 2013 Citation: Smith, M.W. 2013. Kernel necrosis. Western Pecan Growers Assn. Conf. Proc. 47:25.
  • Type: Other Status: Published Year Published: 2014 Citation: Smith, M.W. and W.D. Goff. 2014. Pecan nut suture splits are positively related to kernel moisture concentration and solar radiant exposure. Pecan Grower 24(1):8-12.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2011 Citation: Smith, M.W. February 2011. Benefits of correcting potassium and phosphorus shortages, SE Pecan Growers Assn., Biloxi, MS.


Progress 10/01/12 to 09/30/13

Outputs
Target Audience: Pecan producers and processors in the U.S.A. and elsewhere; scientists and extension personnel working with pecans or those with interests related to the particular research project. Changes/Problems: No changes are planned, simply following the logical progression of information generated from earlier studies on the particular topic. What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? The results of each of these topics have been disseminated to scientists and extension personnel via refereed publications. In addition, each of these topics has been presented at several producer conferences with attendance ranging from 25 to over 300 individuals. In addition, two of these topics were covered at a field day in Georgia with over 400 individuals in attendance. What do you plan to do during the next reporting period to accomplish the goals? Each of these topics requires several years and multiple studies to achieve a resolution to the problem. All of these topics have ongoing research and additional studies planned for 2014.

Impacts
What was accomplished under these goals? The characteristics of “kernel necrosis” have been defined, cultivars identified that are susceptible to this malady and the geographic area where this occurs has been identified and expanded. Several possible causes of this problem have been eliminated by research. Other possible causes, particularly acute susceptibility of certain cultivars to arsenic toxicity, are being investigated. Research has demonstrated banding phosphorus and potassium over drip irrigation lines effectively increased uptake resulting in correcting shortages and improving nut quality and yields. Additional research is underway to refine application times to achieve the greatest return on investment. Research has demonstrated the relationship between selective removal of inferior pecan trees, remaining old trees and survival and growth of newly transplanted trees. A surprising result of this study was a strongly positive relationship between distance from the remaining stump and growth of the transplant. This study will continue to determine initial productivity of the young trees and then data will be subjected to economic analysis to provide producers needed information to guide decisions and secure needed loans.

Publications

  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Smith, M.W. 2013. What do we know about kernel necrosis? Western Pecan Growers Assn. March 3-5, Las Cruces, MN. Smith, M.W. 2013. Banding fertilizers in pecan orchards. Georgia Pecan Growers Assn., March 24-27, Perry, GA.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Shefali, D., C. Rohla, G. Zhang, C. Timmons, J. Blanton, M. Smith, and L.M. Ma. 2013. Occurrence of human pathogens in pre-harvest pecan production fields. 1st Intl. Symposium on Pecan and other Carya in Indigenous and Managed Systems. July 17-19, College Station, TX. Smith, M.W. 2013. Managing alternate bearing in pecan. Arkansas Pecan Growers Assn., Aug. 24, Hope, AR.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Shefali, D., C. Timmons, G. Zhang, C. Rohla, M. Smith and L. Ma. 2013. Rapid and sensitive detection of Shiga toxin-producing Escherichia coli in environmental samples by multiplex. Intl Assn. Food Protection, July 28-31, 2013.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Shefali, D., G. Zhang, C. Rohla, M.Smith, and L. Ma. 2013. A simple, sensitive, and cost-effective method for PCR detection of Salmonella in environmental samples. Intl Assn. Food Protection, July 28-31, 2013.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Shefali, D., C. Rohla, G. Zhang, C. Timmons, M. Smith, and L. Ma. 2013. Occurrence of human pathogens in pre-harvest pecan production fields. Intl Assn. Food Protection, July 28-31, 2013
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Smith, M.W. and B.S. Cheary. 2013. Individual shoot defoliation minimally affects pecan return bloom. HortScience 48:314-317.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Smith, M.W., W.D. Goff, and M.L. Wells. 2013. Pecan orchard renewal: influence of established trees and remaining stumps on transplant growth and crown gall infection. HortScience 48:720-723.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Smith, M.W. and B.S. Cheary. 2013. Response of pecan to annual soil band-applications of phosphorus and potassium. HortScience 48:1411-1415.
  • Type: Journal Articles Status: Published Year Published: 2012 Citation: Fine, K.E., M.W. Smith, and J.C. Cole. 2012. Partitioning of nitrogen, phosphorus, and potassium in redbud trees. Sci. Hort. 152:1-8. http://dx.doi.org/10.1016/j.scienta.2013.01.006.


Progress 10/01/11 to 09/30/12

Outputs
OUTPUTS: Alternate bearing is the most important horticultural problem facing pecan production. Management can substantially reduce the natural tendency for irregular bearing. Mineral nutrition is one component to minimize crop fluctuations. Banding high rates of potassium (K) and phosphorus (P) increased leaf concentrations of those elements. Return bloom was slightly increased by K and substantially increased by P. When trees received both elements, they acted synergistically increasing return bloom. Data also indicated that the amount of P and K absorbed early in the season was influence by the crop load, long before the developing fruit were a significant sink for nutrients. There is little information relating vegetation management on the orchard floor to performance of bearing pecan trees. Maintaining vegetation free circles surrounding bearing trees increased six year cumulative yields over 2 fold compared to mowing the vegetation surrounding the tree. Currently, the most widely planted pecan cultivar in the U.S.A. is Pawnee. In certain locations it develops necrotic tissue at the basal end of the kernel making it unmarketable in the high-value retail market. The cause of kernel necrosis is unknown; however, several hypotheses have been developed and are being tested. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: The information generated by this research will be utilized by extension personnel and commercial laboratories to make fertilizer recommendations benefiting pecan producers in Oklahoma and elsewhere. Results of the nutrition studies have resulted in changes to standards used to make recommendations. Information regarding vegetation management will be used by extension personnel and commercial pecan producers. Information has been distributed through appropriate channels. Information regarding kernel necrosis of Pawnee has not solved the problem, but is part of a methodical approach to solve this perplexing problem troubling one of the most popular cultivars planted today. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Fertility recommendations for pecan are based on leaf elemental composition. Data from these studies indicated that current standards for P and K were too low; resulting in lower kernel quality during years with heavy crop loads and suppressed return bloom. The minimum leaf P concentration has been increased from 0.12% to 0.14% and K from 0.75% to 1%. This will have a substantial impact on producers; particularly during years when production is heavy since nut quality will be higher commanding a higher price and the subsequent year's crop will be larger. This information has been included in technical and producer publications summarizing nutritional requirements for pecan, and was the feature on the cover of a producer magazine. Pecan trees were managed with various sizes of vegetation free zones surrounding the tree from 0 to 7.3 m diameter from planting through their sixth production year. Cumulative yield was increased over 2 fold using 7.3 m diameter vegetation free compared to no vegetation control other than mowing. Pecan producers are improving their ground cover management as a result of this information. Kernel necrosis on Pawnee pecan remains an elusive problem. Neither Cu nor Ni supplemental foliar applications affected the incidence of kernel necrosis. Current data indicates this problem has been identified in the Red River Basin, Rio Grande Basin and one orchard near the Arkansas River. The most likely cause appears to be nutritional, but studies to date have failed to resolve the problem. Elements that are abnormally high in pecan afflicted with kernel necrosis are Li and As, and Co is unusually low. Studies are in progress to determine the potential contribution of these elements to this problem.

Publications

  • Smith, M.W. 2012. Fruit production characteristics of Pawnee pecan. 24(2):58-65.
  • Smith, M.W. 2012. Fruit production characteristics of Pawnee pecan. HortScience 47:489-496.
  • Smith, M.W. 2012. Kernel necrosis of Pawnee pecan: Expanded distribution and relation to yield, tree size and canopy location. HortScience 47:465-467.
  • Hardin, J.A., M.W. Smith, P.R. Weckler, and B.S. Cheary. 2012. In situ measurement of pecan leaf nitrogen concentration using a SPAD meter and Vis-NIR multispectral camera. HortScience 47:955-960.
  • Smith, M.W., C.R. Rohla, and W.D. Goff. 2012. Pecan leaf elemental sufficiency ranges and fertilizer recommendations. HortTechnology 22:594-599.
  • Smith, M.W. 2012. Vegetation control improves pecan production. Pecan Grower 23(3):26-31.
  • Smith, M.W. 2012. Re-evaluation of potassium and phosphorus requirements. Western Pecan Growers Assn. Conf. Proc. 46:40-43.
  • Goff, B. and M.W. Smith. 2012. Major changes in how to fertilize pecan trees. Pecan South 45(7)4, 18, 20.
  • Smith, M.W. 2012. Kernel necrosis of Pawnee pecan. Pecan South 45(7):40-45.


Progress 10/01/10 to 09/30/11

Outputs
OUTPUTS: Alternate bearing is the most important horticultural problem facing pecan production. Management can substantially reduce the natural tendency for irregular bearing. Mineral nutrition is one component to minimize crop fluctuations. Banding high rates of potassium (K) and phosphorus (P) increased leaf concentrations of those elements. Return bloom was slightly increased by K and substantially increased by P. When trees received both elements, they acted synergistically increasing return bloom. Data also indicated that the amount of P and K absorbed early in the season was influence by the crop load, long before the developing fruit were a significant sink for nutrients. Nickel (Ni) is a recently recognized essential element. Baseline data was not available concerning leaf Ni standards to guide fertility recommendations. Two studies were conducted using foliar applied Ni in orchards where Ni was thought to be deficient. One study indicated the minimum sufficiency for leaf Ni using standard index tissue and time was 2.9 g dry weight. Another study in an orchard where pecan kernel necrosis persisted indicated that neither Ni nor Cu foliar applications affected the incidence of kernel necrosis. There is little information relating vegetation management on the orchard floor to performance of bearing pecan trees. Maintaining vegetation free circles surrounding bearing trees increased six year cumulative yields over 2 fold compared to mowing the vegetation surrounding the tree PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: The information generated by this research will be utilized by extension personnel and commercial laboratories to make fertilizer recommendations benefiting pecan producers in Oklahoma and elsewhere. Results of the nutrition studies have resulted in changes to standards used to make recommendations. Information regarding vegetation management will be used by extension personnel and commercial pecan producers. Information has been distributed through appropriate channels. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Fertility recommendations for pecan are based on leaf elemental composition. Data from these studies indicated that current standards for P and K were too low; resulting in lower kernel quality during years with heavy crop loads and suppressed return bloom. The minimum leaf P concentration has been increased from 0.12% to 0.14% and K from 0.75% to 1%. This will have a substantial impact on producers; particularly during years when production is heavy since nut quality will be higher commanding a higher price and the subsequent year's crop will be larger. The initial survey of orchards suggested that Ni shortages were unlikely in the northern two-thirds of Oklahoma, but the lower one-third, particularly in the Red River Basin, the probability of deficiencies was moderate to high. Results indicated no response to Ni above a 2.9 g leaf concentration, thus lowering the currently recognized minimum sufficiency level for Ni. Kernel necrosis on Pawnee pecan remains an elusive problem. Neither Cu nor Ni supplemental foliar applications affected the incidence of kernel necrosis. Current data indicates this problem is primarily restricted to the Red River Basin. Also the most likely cause appears to be nutritional, but studies to date have failed to resolve the problem.

Publications

  • Smith, M.W. and P. Weckler. 2011. Industry driven pecan research and extension priorities. Proc. Okla. Pecan Growers Assn. 81:13-17.
  • Smith, M.W. 2011. Vegetation control improves pecan production. Proc. Okla. Pecan Growers Assn. 81:36-39.
  • Smith, M.W. (ed). 2011. Proc. Okla. Pecan Growers Assn. vol. 81. pp. 39
  • Wagle, P., M.W. Smith, B.W. Wood, and C.T. Rohla. 2011. Response of young bearing pecan trees to spring foliar nickel applications. J. Plant Nutrition 34:1558-1566.
  • Wagle, P., M.W. Smith, B.W. Wood, and C.T. Rohla. 2011. Supplemental foliar nickel and copper applications do not reduce kernel necrosis in pecan trees receiving excess nitrogen. Commun. Soil Sci. Plant Analy. 42:2219-2228.
  • Smith, M.W. 2011. Pecan production increased by larger vegetation-free area surrounding the tree. Sci. Hort. 130:211-213.
  • Smith, M.W. and P. Weckler. 2011. Industry driven pecan research and extension priorities. Pecan Grower. 22(4):80-83.
  • Smith, M.W. and P. Weckler. 2011. Industry meets to pinpoint research, extension priorities. Pecan South 44(2):14, 15-17,18.


Progress 10/01/09 to 09/30/10

Outputs
OUTPUTS: Alternate bearing is the most important horticultural problem facing pecan production. Management can substantially reduce the natural tendency for irregular bearing. Mineral nutrition is one component to minimize crop fluctuations. Return bloom of Pawnee was closely, positively correlated with leaf potassium (K) concentration and weakly correlated with kernel quality. Leaf phosphorus (P) concentrations were closely linked to kernel quality, but not to return bloom. Data also indicated that the amount of P and K absorbed early in the season was influence by the crop load, long before the developing fruit were a significant sink for nutrients. Subsequent research uses replicated treatments to refine the information gleaned from correlations to define minimum sufficiency standards for K and P and confirm observations related to kernel quality and return bloom. Nickel (Ni) is a recently recognized essential element. Baseline data is not available concerning leaf Ni standards to guide fertility recommendations. Three studies were initiated using foliar applied Ni in orchards where Ni was thought to be deficient. Freezing temperatures during the spring as pecan trees break bud can destroy the crop imparting severe economic damage. In 2009, damaging temperatures occurred on 7 April allowing evaluation of several cultivars for bud survival. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: The information generated by this research will be utilized by extension personnel and commercial laboratories to make fertilizer recommendations benefiting pecan producers in Oklahoma and elsewhere. Results of these studies have resulted in changes to standards used to make recommendations. Cultivar evaluations for frost tolerance will assist pecan producers in assessing risk associated with choosing certain cultivars. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Fertility recommendations for pecan are based on leaf elemental composition. These are influenced by crop load. Data from these studies indicated that current standards for P and K were too low; resulting in lower kernel quality during years with heavy crop loads and suppressed return bloom. The minimum leaf P concentration has been increased from 0.12 percent to 0.14 percent and K from 0.75 percent to 1 percent. This will have a substantial impact on producers; particularly during years when production is heavy since nut quality will be higher commanding a higher price and the subsequent year's crop will be larger. The initial survey of orchards suggested that Ni shortages were unlikely in the northern two-thirds of Oklahoma, but the lower one-third, particularly in the Red River Basin, the probability of deficiencies was moderate to high. Results from the first year indicated that Ni improved nut quality. Data indicated no response to Ni above 2.8 micrograms per gram lowering the currently recognized minimum sufficiency level for Ni. Three cultivars of ten evaluated were judged superior in bud survival, Giles, Kanza and Mount, Each of the cultivars with superior survival were of northern origin.

Publications

  • Smith, M.W. and B.S. Cheary. 2010. Relationship of leaf necrosis and defoliation to phosphorus and potassium concentrations in selected tissue and to certain fruit quality parameters of pecan. Sci. Hort. 125:117-122. Smith, M.W. and B.S. Cheary. 2010. Pecan bud damage caused by freezing temperatures during Spring 2009 was affected by cultivar. J. Amer. Pomological Soc. 64:92-100. Smith, M.W. 2010. Phosphorus, potassium affect leaf necrosis, fruit quality and return bloom. Pecan South 43(7):26-27, 30-39.


Progress 10/01/08 to 09/30/09

Outputs
OUTPUTS: Alternate bearing is the most important horticultural problem facing pecan production. Management can substantially reduce the natural tendency for irregular bearing. Mineral nutrition is one component to minimize crop fluctuations. Return bloom of Pawnee was closely, positively correlated with leaf potassium (K) concentration and weakly correlated with kernel quality. Leaf phosphorus (P) concentrations were closely linked to kernel quality, but not to return bloom. Data also indicated that the amount of P and K absorbed early in the season was influence by the crop load, long before the developing fruit were a significant sink for nutrients. Nickel (Ni) is a recently recognized essential element. Baseline data is not available concerning leaf Ni standards to guide fertility recommendations. Three studies were initiated using foliar applied Ni in orchards where Ni was thought to be deficient. Ice storms and other meteorological events can reek havoc on perennial tree crops. A series of four ice storms struck Oklahoma between 2000 and 2008 that caused varying amounts of canopy damage to pecan orchards. This provided a unique opportunity to gather data concerning tree survival, crop loss, recovery time, and costs of orchard clean-up. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Fertility recommendations for pecan are based on leaf elemental composition. These are influenced by crop load. Data from these studies indicated that current standards for P and K were too low; resulting in lower kernel quality during years with heavy crop loads and suppressed return bloom. The minimum leaf P concentration has been increased from 0.12% to 0.14% and K from 0.75% to 1%. This will have a substantial impact on producers; particularly during years when production is heavy since nut quality will be higher commanding a higher price and the subsequent year's crop will be larger. The initial survey of orchards suggested that Ni shortages were unlikely in the northern two-thirds of Oklahoma, but the lower one-third, particularly in the Red River Basin, the probability of deficiencies was moderate to high. Results from the first year indicated that Ni improved nut quality. At least two years data from the three studies will be necessary to establish initial base thresholds for leaf Ni concentration to guide fertility recommendations. There has been a dearth of information concerning the impact of ice damage on pecan production, recovery, and the cost of clean-up. Following a severe icing event producers, insurance companies and the USDA are seeking information, but there has been little available. A publication has documented clean-up costs, tree damage and recovery following ice storms. This information was utilized following the ice storm in Kentucky during 2009. It will serve as a reference for many years.

Publications

  • Smith, M.W. and C.T. Rohla. 2009. Pecan orchard damage and recovery from ice storms. HortTechnology. 19:83-90. Smith, M.W. 2009. Partitioning phosphorus and potassium in pecan trees during high- and low-crop years. J. Amer. Soc. Hort. Sci. 134:399-404. Wagle, P., M.W. Smith, B.W. Wood, B.S. Cheary, B.L. Carroll, C. Reilly, and C.T. Rohla. 2009. Influence of foliar application of nickel and copper on leaf elemental concentration and pecan performance. 20th Annual OSU Research Symposium and Research Scholar Conference, Feb. 18-20 (abstr.). Smith, M.W. 2009. Relationship of leaf necrosis and defoliation to phosphorus and potassium concentrations in selected tissue and to certain fruit quality parameters of pecan. HortScience 44:1110-1111 (abstr.). Smith, M.W. 2009. Partitioning of phosphorus and potassium in pecan trees in relation to annual crop intensity. HortScience 44:1126 (abstr.). Wagle, P., M.W. Smith, B.W. Wood, C.T. Rohla and C.C. Reilly. 2009. Foliar application of nickel and copper on pecan performance. HortScience 44:1119 (abstr.). Smith, M.W. and C.T. Rohla. 2009. Pecan orchard damage and recovery from ice storms. Pecan South 41(12):24-30. Rohla, C.T., M.W. Smith and N.O. Maness. 2009. The influence of cluster thinning on return bloom, nut quality, and concentrations of potassium, nitrogen and non-structural carbohydrates. Pecan Grower 20(3):50-57. Smith, M.W. 2009. Pecan kernel necrosis. Aust. Nutgrower 23(2):24-28. Smith, M.W. 2009. Cause of kernel necrosis remains elusive; input sought. Pecan South 42(5):24-30. Smith, M.W. and B.S. Cheary. 2009. 2009 spring freeze damage. Okla. Pecan Growers Assn Newsletter 50(3):2-6. Smith, M.W. and B.W. Wood. 2009. Study assesses early spring and mid summer nitrogen applications. Pecan South 42(7):30-37. Smith, M.W. (ed.). 2009. Oklahoma Pecan Growers Association Newsletter. vol. 1-4. Smith, M.W. (ed.). 2009. Proceeding Oklahoma Pecan Growers Association. vol. 79. Smith, M.W. 2009. New farm statistics. Okla. Pecan Growers Assn. Newsletter 50(2): 1-6. Smith, M.W. 2009. Horticulture pecan research endowment. Okla. Pecan Growers Assn. Newsletter 50(2): 7 Smith, M.W. 2009. Tree transplanting. Okla. Pecan Growers Assn. Newsletter 50(1): 1-3 Stafne, E.T., M.W. Smith, P.G. Mulder., Jr., D.L. Smith, and C.T. Rohla. 2008. A pocket guide to Oklahoma pecan diseases, insects, and other disorders. Okla. Coop. Ext. Ser. E-1009.


Progress 10/01/07 to 09/30/08

Outputs
OUTPUTS: Alternate bearing is the most important horticultural problem facing pecan production. Research concerning the underlying causes and methods to reduce alternate bearing are a high priority. Fundamental information concerning the relationship of non-structural carbohydrates, organically bound nitrogen, potassium and genotype on alternate bearing has been completed. This information has been published in a series of refereed journal articles, producer publications, and results presented at the Oklahoma and Georgia Pecan Producer Meetings and the Southwest Regional Pecan Producers meeting in New Mexico. Findings of these studies are being incorporated into Cooperative Extension publications and presentations. Pecan kernels of certain cultivars develop necrotic, blackened areas at the basal end of the kernel, making the nuts unacceptable. This problem is prevalent on Pawnee and Choctaw and is seen occasionally on other cultivars. It appears that the certain cultivars with Success in their parentage are predisposed to this malady. The number of producers reporting this problem are increasing and the cause of "kernel necrosis" is unknown. Publication in a scientific journal described this malady and characterized its occurrence. The initial hypothesis was excess nitrogen resulted in cotyledon cell damage from accumulation of ureides with catabolism to ammonia. However, data did not support this hypothesis. High level of phenolic compounds in the liquid endosperm suggested that the shikimic acid pathway may be blocked. Several studies are in progress or planned to address this possibility. Characterization of this problem in a scientific publication should serve to alert other professionals to this emerging problem. PARTICIPANTS: Becky Cheary, Becky Carroll, Pradeep Wagle, David Miller, Charles Rohla, Bruce Wood, Charles Rielly TARGET AUDIENCES: Pecan growers and certain other fruit producers PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
One significant finding concerning alternate bearing is that developing fruit did not inhibit return bloom on cultivars with low alternate bearing , but inhibition of return bloom by developing fruit was nearly complete on high alternate bearing cultivars. This finding has significant implications for pecan breeding programs, such that new genotypes may be screened at a young age for alternate bearing by monitoring return bloom of bearing shoots. Otherwise, trees are normally 15- to 20-years-old before alternate bearing can be determined, thus significantly reducing the time required to evaluate this trait. The breeding program at the University of Georgia is testing this result in their breeding program. If the result is confirmed it will be incorporated into other breeding programs. Depletion of non-structural carbohydrates by large crops has been proposed as a key component contributing to alternate bearing in pecan and other crops. However, this research demonstrated that carbohydrates are not closely correlated with return bloom. Another hypothesis suggested that organically bound nitrogen was depleted to a critical level during fruit development, thus inhibiting return bloom. Data did not support either hypothesis. These results will cause scientists to search for other factors regulating alternate bearing. Pecan kernel necrosis is emerging as a significant problem in certain cultivars. Pawnee is currently the most popular cultivar being planted because of its early maturity, large size, productivity and high market value. However, it appears especially susceptible to kernel necrosis. Although the cause of kernel necrosis has not been identified results indicating that the shikimic acid pathway may be blocked suggest certain possible causes. These are under investigation.

Publications

  • Rohla, C.T., M.W. Smith and N.O. Maness. 2007. The influence of cluster thinning on return bloom, nut quality and concentrations of potassium, nitrogen and non-structural carbohydrates. J. Amer. Soc. Hort. Sci. 132:158-165. Xiong, X., G.E. Bell, J.B. Solie, M.W. Smith and B. Martin. 2007. Bermudagrass seasonal response to N fertilization and irrigation detected using optical sensing. Crop Sci. 47:1603-1610. Smith, M.W., C.T. Rohla and N.O. Maness. 2007. Correlations of crop load and return bloom with concentrations of nitrogen, potassium and non-structural carbohydrates. J. Amer. Soc. Hort. Sci. 132:44-51. Rohla, C.T., M.W. Smith, N.O. Maness and W. Reid. 2007. A Comparison of moderate and severe alternate bearing pecan cultivars. J. Amer. Soc. Hort. Sci. 132:172-177. Smith, M.W., B.W. Wood and W.R. Raun. 2007. Recovery and partitioning of nitrogen from early spring and mid summer applications to pecan trees. J. Amer. Soc. Hort. Sci. 132:758-763. Smith, M.W., B.S. Cheary and B.L. Carroll. 2007. The occurrence of pecan kernel necrosis. HortScience 42:1351-1356. Smith, M.W. 2008. Relationship of Trunk Size to Selected Canopy Parameters for Native Pecan Trees. HortScience43:784-786. Smith, M.W. and P.G. Mulder. 2007. Role of cover crops in the management of arthropod pests in orchards. p. 56-73. In. O. Koul and G. W. Cuperus (eds.) Ecologically Based Integrated Pest Management, CABI International, Cambridge, Mass. Smith, M.W. 2007. The influence of nitrogen rate on pecan kernel necrosis, leaf N concentration, yield and nut quality. (abstr.) HortScience 42:443. Rohla, C.T., M.W. Smith, N.O. Maness, and W. Reid. 2007. Influence of cultivar and shoot position on selected pecan characteristics. (abstr.) HortScience 42:457. Smith, M. 2007. The occurrence of pecan kernel necrosis. (abstr.) HortScience 42:956. Smith, M.W. and E. Stafne. 2007. Oklahomas 2007 ice damage. Okla. Pecan Growers Assn. Newsletter 48(1):8. Smith, M.W. and E. Stafne. 2007. January ice storm takes toll on Oklahoma pecans. Pecan South 40(1):24-25. Smith, M.W. 2007. Vegetation-control is essential in young orchard. Pecan Grower 19(1):70. Smith, M.W. 2007. Vegetation-control is essential in young orchards. Okla. Pecan. Growers Assn. Newsletter 48(2):2-3. Smith, M.W. 2007. Notes on the 2007 pecan season. Okla. Pecan Growers Assn. Newsletter 48(3):1-4. Smith, M.W. 2007. Notes on the 2007 growing season. Okla. Pecan Growers Assn. Newsletter 48(4):1-3. Smith, M.W. and E. Stafne. 2007. Pecan orchard establishment. Okla. Pecan Growers Assn. Newsletter 48(4):7-9. Smith, M.W. 2008. Oklahomas 2nd ice storm in 2007. Okla. Pecan Growers Assn. Newsletter 49(1):1-2. Smith, M.W. 2008. The effect of weeds on orchard establishment. Western Pecan Growers Assn. 42:7-8. Rohla, C.T., M.W. Smith, N.O. Maness, and W.Reid. 2008. A comparison of return bloom, and non-structural carbohydrates, nitrogen, potassium concentrations in moderate and severe alternate-bearing pecan cultivars. Pecan Grower 20(1):72-77.


Progress 10/01/06 to 09/30/07

Outputs
OUTPUTS: The most significant horticultural problem facing pecan producers is alternate bearing. Four pecan [Carya illinoinensis (Wangenh.) C. Koch] cultivars were chosen, two with low to moderate and two with severe alternate-bearing tendencies, to compare selected characteristics related to irregular bearing. The cultivars were Colby and Peruque (low to medium alternate-bearing tendency) and Osage and Giles (high alternate-bearing tendency). Vegetative shoots and fruit bearing shoots in the terminal and lateral position on 1-year-old branches were tagged in October, and flowering was determined the following spring. Shoot and root samples were collected while dormant and then analyzed for organically bound nitrogen (N), potassium (K) and non-structural carbohydrate concentrations. As expected, Colby and Peruque had a lower alternate-bearing tendency than Giles and Osage. Cultivars with a low alternate-bearing tendency had a larger return bloom on the bearing shoots in the terminal position than the other shoot types. Cultivars with a high alternate-bearing tendency had a lower return bloom on bearing terminal shoots than vegetative shoots. Bearing shoots in the lateral position usually had a lower return bloom than the other shoot types, regardless of cultivar. Neither root nor shoot N, K or non-structural carbohydrate concentrations appeared to be closely related to the alternate-bearing characteristics of the four cultivars. The unique characteristic identified for low alternate-bearing cultivars was their ability to produce as many or more flowers and flowering shoots the following year on previously bearing terminal shoots compared to previously vegetative shoots. In high alternate-bearing cultivars, return bloom of bearing terminal shoots was suppressed relative to their vegetative shoots. PARTICIPANTS: Individuals Michael Smith (PI) - planned and directed research, participated in all aspects of experimental design, installation, data collection, data analysis and manuscript preparation. Becky Cheary (technician) - participated in experiment installations and data collection. Becky Carroll (technician) - participated in experiment installations and data collection. Partner Organizations USDA - CGC USDA-ARS Noble Foundation Oklahoma Pecan Growers' Association Savage Equipment Co. Montz Pecan Co. Kansas State University Collaborators and contacts Phil Mulder, Dept. of Entomology and Plant Pathology, Oklahoma State University Niels Maness, Dept. of Horticulture and L.A., Oklahoma State University Bruce Wood, USDA-ARS, Byron, GA Bill Reid, Department of Horticulture, Kansas State University

Impacts
Alternate bearing is the number one horticultural problem facing pecan producers. This research repudiates long-held beliefs of the underlying cause of alternate bearing, and recently hypothesized crop culture limitations affecting production consistency. These results should take scientists in new directions to understand flower induction and development of management techniques to improve production consistency.

Publications

  • Smith, M.W. and B.W. Wood. 2006. Pecan tree biomass estimates. HortScience 41:1286-1291.
  • Rohla, C.T., M.W. Smith and N.O. Maness. 2007. The influence of cluster thinning on return bloom, nut quality and concentrations of potassium, nitrogen and non-structural carbohydrates. J. Amer. Soc. Hort. Sci. 132:158-165.
  • Smith, M.W., C.T. Rohla and N.O. Maness. 2007. Correlations of crop load and return bloom with concentrations of nitrogen, potassium and non-structural carbohydrates. J. Amer. Soc. Hort. Sci. 132:44-51.
  • Rohla, C.T., M.W. Smith, N.O. Maness and W. Reid. 2007. A Comparison of moderate and severe alternate bearing pecan cultivars. J. Amer. Soc. Hort. Sci. 132:172-177.
  • Smith, M.W. and P.G. Mulder. 2007. Role of cover crops in the management of arthropod pests in orchards. p. 56-73. In. O. Koul and G. W. Cuperus (eds.) Ecologically Based Integrated Pest Management, CABI International, Cambridge, Mass


Progress 10/01/05 to 09/30/06

Outputs
Vegetation surrounding pecan (Carya illinoinensis Wangenh. C. Koch) trees in a 4.3 m by 6 m area was either controlled with a non-residual herbicide for the entire growing season, not controlled, or controlled at certain times during the growing season. After three growing seasons, trunk diameters were suppressed 54% when vegetation was not controlled, 47% when not controlled until 1 Aug., and 37% if not controlled after 1 June compared to entire growing season vegetation control. Trunk diameters were not significantly different from entire season vegetation control when vegetation was controlled from 1 June through fall frost or vegetation controlled from April until 1 Aug. Vegetation in the plots was typically dominated by cool season herbaceous dicots in May and June, and warm season grasses during August and September.

Impacts
Weed interference is a major limiting factor in establishment, growth and initial production of pecans. This research demonstrates critical periods for vegetation control, and will allow producers to focus inputs at critical times during the growing season.

Publications

  • No publications reported this period


Progress 10/01/04 to 09/30/05

Outputs
Whole fruit clusters of pecan [Carya illinoinensis cv. Pawnee (Wang.) C. Koch.] were collected from three shoot types: terminal and lateral shoots without a secondary growth flush, and shoots that had an early-season secondary growth flush. Fruit per cluster were counted and nuts were individually harvested, weighed, shelled and graded. Bloom the following year was determined for the same shoots where clusters were collected. Wafers (cotyledons that failed to develop) were not associated with cluster size or shoot type. When wafers were included in the data, nut weight, kernel percentage and return bloom were not affected by cluster size or shoot type. However, when wafers were excluded from the data there were significant relationships of cluster size and shoot type with the dependent variables. Cluster size on lateral shoots was negatively related to nut weight and kernel percentage. Cluster size on terminal shoots without a secondary growth flush was inversely related to kernel percentage, but not related to nut weight. When shoots had a secondary growth flush, cluster size was not related to kernel percentage or nut weight. There was a positive linear relationship between cluster size and total kernel weight for the three shoot types. Return bloom of terminal shoots without a secondary growth flush was negatively related to cluster size, but cluster size did not affect return bloom of the other shoot types. The number of shoots that developed the following year was positively related to cluster size for terminal and lateral shoots, but not for shoots with a secondary growth flush. Shoots with a secondary growth flush produced substantially more shoots with larger fruit clusters the next year than the other shoot types.

Impacts
Alternate bearing remains the dominate horticultural problem facing pecan producers. This research addresses fundamental questions concerning alternate bearing and these results shed new light on underlying causes, creating a new paradigm for fundamental research concerning irregular bearing.

Publications

  • Smith, M.W., B.S. Cheary, and B.L. Carroll. 2005. Temporal weed interference with young pecan trees. HortScience 40:1723-1725.
  • Smith, M.W., B.S. Cheary, and B.L. Carroll. 2004. Response of pecan to nitrogen rate and nitrogen application time. HortScience 1412-1415.
  • Rohla, C.T., M.W. Smith. and N.O. Maness. 2005. Effects of cluster size and shoot type on selected pecan characteristics. HortScience 40:1300-1303.
  • Smith, M.W., B.S. Cheary, and B.L. Carroll. 2005. Size of vegetation free area affects non-bearing pecan tree growth. HortScience 40:1298-1299.


Progress 10/01/03 to 09/30/04

Outputs
Whole fruit clusters of pecan [Carya illinoinensis (Wang.) C. Koch.] were collected from three shoot types: terminal and lateral shoots without a secondary growth flush, and shoots that had an early-season secondary growth flush. Fruit per cluster were counted and nuts were individually harvested, weighed, shelled and graded. Bloom the following year was determined for the same shoots where clusters were collected. Wafers (cotyledons that failed to develop) were not associated with cluster size or shoot type. When wafers were included in the data, nut weight, kernel percentage and return bloom were not affected by cluster size or shoot type. However, when wafers were excluded from the data there were significant relationships of cluster size and shoot type with the dependent variables. Cluster size on lateral shoots was negatively related to nut weight and kernel percentage. Cluster size on terminal shoots without a secondary growth flush was inversely related to kernel percentage, but not related to nut weight. When shoots had a secondary growth flush, cluster size was not related to kernel percentage or nut weight. There was a positive linear relationship between cluster size and total kernel weight for the three shoot types. Return bloom of terminal shoots without a secondary growth flush was negatively related to cluster size, but cluster size did not affect return bloom of the other shoot types. The number of shoots that developed the following year was positively related to cluster size for terminal and lateral shoots, but not for shoots with a secondary growth flush. Shoots with a secondary growth flush produced substantially more shoots with larger fruit clusters the next year than the other shoot types.

Impacts
Irregular bearing is a major problem in pecan. During high crop years nut quality is frequently low. This study characterized several factors contributing to bearing consistency and nut quality to improve our basic understanding of these two critical components for profitable production. This information will contribute to priorites for pecan breeding programs and crop cultural programs.

Publications

  • Stevenson, D.E., A.E. Knutson, W. Ree, J.A. Jackman, A. Dean, J.H. Matis, J. McVay, M. Nesbitt, R. Mizell, J. Dutcher, W. Reid, M. Hall, D. Barlow, M.T. Smith, P. Mulder, M.W. Smith, J.G. Millar, and M.K. Harris. 2003. Pecan nut casebearer pheromone monitoring and degree-day model validation across the pecan belt. Southwest Entomologist Suppl. No. 27:57-73.
  • Smith, M.W., B.S. Cheary, and B.L. Carroll. 2004. Response of pecan to nitrogen rate and nitrogen application time. HortScience 1412-1415.
  • Rohla, C.T., M.W. Smith, N.O. Maness and W. R. Reid. 2004. Crop load and shoot type affect return bloom of pecans. HortScience 39:814.
  • Rohla, C.T., M.W. Smith, N.O. Maness and W. R. Reid. 2004. Effects of fruit cluster size and shoot type on selected pecan characteristics. HortScience 39:814.
  • Morrison, A.A., M.W. Smith, and P.G. Mulder. 2004. Can we delay budbreak in pecan? Proc. Okla. Pecan Growers Assn. 74:35-36.
  • Rohla, C., M.W. Smith, and N. Maness. 2004. How crop load and cluster size affects return bloom, nut quality, and stored nitrogen and potassium. Proc. Okla. Pecan Growers Assn. 74:29-34.
  • Smith, M.W. 2004. Managing nitrogen, phosphorus, and potassium needs for pecan orchards. Proc. Okla. Pecan Growers Assn. 74:59-67.
  • Smith, M.W. 2004. Fruit thinning improves nut quality and return bloom of pecan trees. Proc. Western Pecan Conf. 38:142-144.
  • Smith, M.W. 2004. Managing nitrogen, phosphorus and potassium needs for pecan orchards. Proc. Western Pecan Conf. 38:99-107.


Progress 10/01/02 to 09/30/03

Outputs
Nitrogen was applied between 1996 and 2002 to grafted Mohawk pecan (Carya illinoinensis Wangenh. C. Koch.) trees at 75 or 150 kg ha-1 either as a single application in March or as a split application with 60 percent applied in March and 40% the first week of June. In 1997 and 2001, a spring freeze damaged developing shoots and buds, resulting in a small, non-commercial crop and the June portion of the N application was withheld. Nitrogen was also applied during the first week in October at 0 or 50 kg ha-1 N if the crop load before fruit thinning in August was ≥ 40 percent fruiting shoots. There were few differences in the percentage of fruiting shoots or cluster size associated with N rate or applying N as a single or split application. Leaf N concentrations were either not affected by treatment or the results were inconsistent. Omitting the June application when a crop failure occurred did not affect the percentage of fruiting shoots the following year. October N application either did not affect or reduced the percentage of fruiting shoots the following year, and had no influence on leaf N concentration in July or October. These results indicate that the only advantage of a split N application is the option of withholding the second portion in the event of a crop failure. However, the added expense associated with splitting the N application versus the risk of crop failure must be assessed for each situation to determine if this is a sound economic practice. These data do not support an October N application when the crop is ≥ 40 percent fruiting shoots to reduce irregular bearing.

Impacts
Many pecan growers have recently adapted fall N applications to increase return bloom following a large crop. This research demonstrated that fall N does not affect return bloom. Therefore, growers can reduce expenses and should avoid fall N application; a time when the likelihood of N leaching into the ground water is high. The research also suggests that a single spring N application is as effective as a split application. The chief advantage of a split spring application is the ability to adjust N rate in the event of a crop loss.

Publications

  • Acuna-Maldonado, L.E., M.W. Smith, N. O. Maness, B.S. Cheary, B.L. Caroll, and G.V. Johnson. 2003. Influence of nitrogen application time on nitrogen absorption, partitioning, and yield of pecan. J. Amer. Soc. Hort. Sci. 128:155-162.
  • Smith, M.W. 2003. Mineral nutrition. p. 317-348. In. D.W. Fulbright (ed.) A Guide to Nut Tree Culture in North America, Vol. 1. Northern Nut Growers Assn., Inc.
  • Smith, M.W. 2003. Factors affecting induction and differentiation of pistillate flowers on pecan trees. Western Pecan Conf. Proc. 37:34-38.
  • Smith, M.W. 2003. Recent information for managing nitrogen nutrition for pecan. Texas Pecan Growers Assn. 81&82:37.


Progress 10/01/01 to 09/30/02

Outputs
Newly planted pecan (Carya illinoinensis Wangenh. C. Koch) trees were grown for three years in a tall fescue (Festuca arundinacea Shreb. cv. Kentucky 31) sod with vegetation free circles 0, 0.91, 1.83, 3.66, or 7.32 m in diameter. Trees were irrigated to minimize growth differences associated with water competition from fescue, although some moisture competition occurred. There were no differences among treatments in total shoot growth after one year, but trunk growth was increased by vegetation free areas. During the second year, trees with a 0.91 m wide vegetation free area had twice as much shoot growth and trunks were two times larger than those without a vegetation free zone. The third year, trees with a 0.91 m wide vegetation free circle had 403 percent more new shoot growth and trunks were 202 percent larger than those without a vegetation free zone. Cumulative shoot growth was up to 559 percent greater with vegetation control. Tree growth was similar with a 1.83 or 3.66 m wide vegetation free circle, and trees in both treatments were larger than trees with 0 or 0.91 m wide vegetation free zones. Extending the vegetation free zone to 7.32 m wide was not advantageous. Competition from fescue reduced some pecan leaf elemental concentrations, particularly N, and decreased moisture availability.

Impacts
(N/A)

Publications

  • Smith, M.W. 2000. Cultivar and mulch affect cold injury of young pecan trees. J. Amer. Pomological Soc. 54:29-33.
  • Smith, M.W., B.L. Carroll, and B.S. Cheary. 2000. Mulch improves pecan tree growth during orchard establishment. HortScience 35:192-195.
  • Smith, M. W. 2002. Damage by an early autumn freeze varies with pecan cultivar. HortScience 37:398-401.


Progress 10/01/00 to 09/30/01

Outputs
An exceptionally early autumn freeze on 8 and 9 October 2000 injured young pecan trees. Cold injury was rated in an existing rootstock and cultivar trial. There was less injury to current season's growth on 'Kanza' than on 'Mohawk', 'Mount' and 'Creek'. Trees on rootstocks of 'Peruque', 'Giles', 'Colby', 'Apache', and native seedlings from Stillwater, Okla. and Brunswick, Mo. were among the least injured by the fall freeze. Trees on 'Starking Hardy Giant' and natives from Chetopa, Kans. were the most severely injured by the freeze. Cold hardiness imparted to the scion by the rootstock was not closely related to the climate at the rootstock's origin. Non-bearing and bearing cultivars were rated for cold injury at four sites. Non-bearing cultivars with little or no damage included 'Caddo', 'Clark II', 'Giles', 'Kanza', and 'Peruque'. Those that had substantial damage included 'Maramec', 'Pawnee', 'Oconee', 'Shawnee' and 'OK642'. Bearing cultivars with little or no injury included 'Stuart', 'GraKing', 'Pawnee', 'Tejas' and 'Wichita'. The most severely damaged bearing cultivars were 'Gratex', 'Shoshoni' and 'Squirrel's Delight'.

Impacts
(N/A)

Publications

  • Smith, M. W. 2001. Pecan cultivars are damage by an early autumn freeze. HortScience (accepted for publication).
  • Smith, M.W., B. S. Cheary and B. L. Carroll. 2001. Rootstock and scion affect cold injury of young pecan trees. J. Amer. Pomological Soc. 55:124-128.
  • Smith, M. W., B. S. Cheary, and B.S. Landgraf. 2001. Manganese deficiency in pecan. HortScience 36:1075-1076.
  • Smith, M. W., M. E. Wolf, B.S. Cheary, and B. L. Carroll. 2001. Allelopathy of bermudagrass, tall fescue, redroot pigweed and cutleaf evening primrose on pecan. HortScience 36:1047-1048.


Progress 10/01/99 to 09/30/00

Outputs
Growth of `Apache' pecan (Carya illinoensis Wangenh. K. Koch) seedlings was evaluated for 3 years when grown in a 11.2 m2 weed-free area or when various combinations of one or two plants of cutleaf evening primrose (Oenothera laciniata Hill), a cool season species, or Palmer amaranth (Amaranthus palmeri S. Wats.), a warm season species, were grown 30 cm from the tree, with the rest of the 11.2 m2 area weed-free. Either weed species alone suppressed tree growth compared to the weed-free control. A temporal succession of primrose followed by amaranth reduced growth most. After 3 years, two plants of primrose followed by two of amaranth caused a 79% reduction in cumulative current season's growth. `Giles' pecan seedlings were either not mulched or mulched with wood chips arranged in a 1- or 2-m wide square that was 30 cm deep. Mulch treatments were in factorial combination with two N rates applied as either a single application at budbreak or as a split application at budbreak and 3 weeks later. Tree height was positively related to mulch width each year of the 3-year study, and trunk diameter was positively related to mulch width during the second and third years of the experiment. Trees receiving the higher N rate were taller during 2 of 3 years, but leaf N concentration was not affected by N rate. No differences in the parameters measured were observed when N was applied as a single or split application.

Impacts
(N/A)

Publications

  • Smith, M.W., B.S. Cheary, and B.L. Carroll. 1999. Growth characteristics of selected pecan rootstocks prior to grafting. Fruit Varieties J. 53:40-48.
  • Wolf, M.E. and M.W. Smith. 1999. Cutleaf evening primrose and palmer amaranth interference with growth of non-bearing pecan trees. HortScience 34:1082-1084.
  • Smith, M.W. 2000. Cultivar and mulch affect cold injury of young pecan trees. J. Amer. Pomological Soc. 51:29-33.
  • Smith, M.W., B.L. Carroll, and B.S. Cheary. 2000. Mulch improves pecan tree growth during orchard establishment. HortScience 35:192-195.


Progress 10/01/98 to 09/30/99

Outputs
Growth of `Apache' pecan (Carya illinoensis Wangenh. K. Koch) seedlings was evaluated for 3 years when grown in a 11.2 m2 weed-free area or when various combinations of one or two plants of cutleaf evening primrose (Oenothera laciniata Hill), a cool season species, or Palmer amaranth (Amaranthus palmeri S. Wats.), a warm season species, were grown 30 cm from the tree, with the rest of the 11.2 m2 area weed-free. Either weed species alone suppressed tree growth compared to the weed-free control. A temporal succession of primrose followed by amaranth reduced growth most. After 3 years, two plants of primrose followed by two of amaranth caused a 79% reduction in cumulative current season's growth.

Impacts
(N/A)

Publications

  • Smith, M.W., B.S. Cheary, and B.L. Carroll. 1999. Growth characteristics of selected pecan rootstocks prior to grafting. Fruit Varieties J. 53:40-48.
  • Wolf, M.E. and M.W. Smith. 1999. Cutleaf evening primrose and palmer amaranth interference with growth of non-bearing pecan trees. HortScience 34:1082-1084.
  • Mulder, Jr., P.G., R.A. Grantham, M.W. Smith, and B.S. Cheary. 1999. Pecan weevil control in pecans, Sparks, OK, 1998. Arthropod Management Tests 24:94.
  • Acuna-Maldonado, L.E. and M.W. Smith. 1999. Effect of nitrogen fertilization time on nitrogen storage and return bloom of pecan. HortScience 34:492.
  • Smith, M.W. 1999. El aclareo mejora la calidad y floracion subsecuente en arboles de nogal pecanero. Septimo Simposium Internacional Nogalero, Nogatec. 99:21-24.


Progress 10/01/97 to 09/30/98

Outputs
Six pecan (Carya illinoinensis (Wangenh.) K. Koch) cultivars and five pecan families (closely related individuals from a native population) were evaluated for use as rootstocks. The evaluation period was from seed planting through 4-years-old, but before the rootstocks were grafted. 'Apache' rootstocks grew more rapidly than the other rootstocks tested during the first two years. However, by the fourth year 'Apache' and 'Peruque' trees were similar in height, and trunk diameters of 'Apache', 'Giles' and 'Peruque' were similar. Coefficients of variation for tree heights and trunk diameters indicated that variability between individuals was similar within cultivars and families. Budbreak date was strongly influenced by rootstock, with up to a 14 day difference between the first and last rootstocks to attain 90% budbreak. An April freeze damaged current season's growth on 90% of the 'Apache' trees, but only 10% of the 'Giles', 'Hardy Giant', and natives from Chetopa, KS and Sapulpa, OK were injured. Freeze damage was dependent on the bud developmental stage. Several significant differences in leaf elemental concentrations between rootstocks were identified.

Impacts
(N/A)

Publications

  • Smith, M.W., B.S. Cheary, and B.L. Carroll. 1997. Effect of water bath temperature and stratification on germination of pecan seed. HortScience 32:1272-1273.
  • McCraw, B.D. and M.W. Smith. 1998. Root pruning and soil type affect pecan root regeneration. HortTechnology 8:18-20.
  • Rice, N.R., M.W. Smith, R.D. Eikenbary, D. Arnold, W. L. Tedders, B. Wood, B.S. Landgraf, G.G. Taylor, and G.E. Barlow. 1998. Assessment of legume and non-legume ground covers on Coleoptera: Coccinellidae density for low-input pecan management. Amer. J. Alt. Agri. 13: 2-14.
  • Mulder, Jr., P.G., J.K. Collins, R.A. Grantham, M.W. Smith and B.D. McCraw. 1997. Control of pecan nut casebearer in pecans, 1996. Arthropod Management Tests 22:77.
  • Mulder, Jr., P.G., J.K. Collins, and M.W. Smith . 1977. Control of pecan nut casebearer and fall webworm in pecans, 1996. Arthropod Management Tests 22:78.


Progress 10/01/96 to 09/30/97

Outputs
An annual legume cover crop was evaluated in pecan orchards to increase coccinellids that would reduce pecan aphids. Treatments were a 'Dixie' crimson clover and hairy vetch mixture and a grass sod. Coccinellids were abundant on the legume ground covers, but coccinellid denisty in the tree canopy was rarely affected by ground cover treatment. There were substantial differences in the coccinellid species collected from the legumes vs. the trees. In Oklahoma, the main species in the tree were Olla v-nigrum (Mulsant) and Cycloneda munda (Say), and in the legumes Hippodamia convergens Guerin, Coccinella septempunctata L., and Coleomegilla maculata lengi Timberlake were the dominant species. In Georgia, Harmonia axyridis (Pallas) was the dominant species in the trees, and C. septempunctata in the legumes. Pecan aphids at two Oklahoma sites were usually not affected by cover crop treatment, but early season aphids were frequently lower at the Georgia site using a legume cover crop compared to a grass sod. The accumulated effect of all aphid predators and parasitoids attracted to the legume aphids may have contributed to the pecan aphid reduction.

Impacts
(N/A)

Publications

  • Thompson, T.E., L.J. Grauke, W. Reid, M.W. Smith, and S.R. Winter. 1997. 'Kanza' pecan. HortScience 32:139-140.


Progress 10/01/95 to 09/30/96

Outputs
Crimson clover (Trifolium incarnatum L.) plus hairy vetch (Vicia villosa Roth), red clover (Trifolium pratense L.), white clover (Trifolium repensL.), red clover plus white clover, and bermudagrass (Cynodon dactylon (L.)Pers.) were evaluated as ground covers for pecans. Crimson clover plus hairy vetch supplied the equivalent of 101 to 159 kg N/ha. Red clover plus white clover supplied up to 132 kg N/ha. Either white clover or red clover alone were less effective in supplying N than when grown together. Soil Kjeldahl-N was usually not affected or increased using the legumes compared to fertilized bermudagrass sod. Soil NO3 concentrations during October were occasionally higher in unfertilized legume plots than March applied N to bermudagrass plots.

Impacts
(N/A)

Publications

  • Smith, M.W., D.C. Arnold, R.D. Eikenbary, N.R. Rice, A. Shiferaw, B.S.Cheary, and B.L. Carroll. 1996. Influence of ground cover on beneficial arthropods in pecan trees. Biological Control 6:164-176.
  • Smith, M.W., D.C. Arnold, R.D. Eikenbary, N.R. Rice, A. Shiferaw, B.S.Cheary, and B.L. Carroll. 1996. Influence of ground cover on phytophagous and saprophagous arthropods in pecan trees. Southwestern Entomol.21:303-315.
  • Smith. M.W., A. Shiferaw, and N.R. Rice. 1996. Legume ground covers as anitrogen source in pecan. J. Plant Nutrition 19:111-1124.


Progress 10/01/94 to 09/30/95

Outputs
Arthropods were collected, identified and counted on three dates to determine the effects of ground cover on arthropod type and density in pecan canopies. Ground covers were a grass sod (primarily bermudagrass, Cynodon dactylon (L.) Pers.), red clover (Trifolium pratense L.), or a mixture of crimson clover (T. incarnatum L.) and hairy vetch (Vicia villosa Roth.). Arthropods collected represented eight orders of Insecta, three orders of Arachnida, plus one Chilopoda. Ground cover had little effect on the density or type of arthropods present in the pecan canopy, except densities of Chrysoperla rufilabris (Burmeister) were greater during July from pecans with a legume ground cover than a grass ground cover. C. rufilabris is a major predator of aphids, that may supress pecan aphid density. Other staistically significant differences in arthropod densities between ground cover types were not of practical importance.

Impacts
(N/A)

Publications


    Progress 10/01/93 to 09/30/94

    Outputs
    Pecan Carya illinoinensis (Wangenh.) C.Koch fruit were thinned from `Mowhawk' trees in Oklahoma and `Giles' trees in Kansas with a mechanical trunk shaker. All trees bore an excessive crop load before shaking. Fruit thinning improved the kernel percentage, individual nut weight, and kernel grade of `Mowhawk', but nut characteristics of `Giles' were not affected by fruit thinning. Cold injury, caused by a sudden temperature drop in November, was positively related to the percentage of fruiting shoots in both cultivars. Fruit set in 1992 was negatively related to the percentage of fruiting shoots in 1991 in both cultivars. Consistent annual fruit set could be induced in `Giles' by fruit thinning, but return fruit set in `Mowhawk', even at high levels of thinning, was low. Fruit thinning reduced yield the year of thinning in both cultivars. Thus, `Mowhawk' trees should be thinned so that 50% to 60% of shoots bearing fruit at mid-canopy height would remain, and `Giles' trees should be thinned similarly to 65% to 70%.

    Impacts
    (N/A)

    Publications


      Progress 10/01/92 to 09/30/93

      Outputs
      The optimum time for removing pecans (Carya illinoinensis (Wangenh.) K. Koch toenhance return bloom was determined. Fruit were removed from part of `Mohawk', `Giles', and `Gormely' trees five times during the season as determined by fruit phenological age: immediately after postpollination drop, at 50% ovule expansion, at 100% ovule expansion or water stage, during the onset of dough stage, and 2 weeks after dough stage. Return bloom of all cultivars was increased by fruit removal during ovule expansion. Removing `Mohawk' and `Giles' fruit shortly after pollination induced the greatest return bloom. Return bloom in the small-fruited `Gormely' was equally stimulated by fruit removal at any time during ovule expansion, a result indicating that early fruit removal may be more important for large-than for small-fruited cultivars. If a commercially feasible method to thin pecans is developed, our studies indicate that the optimum time for fruit thinning would be during ovule expansion.

      Impacts
      (N/A)

      Publications


        Progress 10/01/91 to 09/30/92

        Outputs
        `Dodd' pecan seedlings Cara illinoinensis (Wangenh.) K.Koch were chilled at 6Cfor 0 to 1800 hours in 300-hour intervals and percent budbreak and days to budbreak recorded. Chilling duration required for />=/50% budbreak was 900 hours. Chilling > 900 hours: increased budbreak percentage and reduced time to budbreak. `Dodd' seedlings chilled at 1, 5, or 9C for 0 to 2500 hours in 500-hour intervals had more lateral budbreak after 1000 hours of chilling at 5C than at 1 or 9C. When chilling hours ranged from 1500 to 2500, 1C increased budbreak of the first lateral bud compared with 5 or 9C. As chilling was increased from 1000 to 2500 hours, the days to budbreak declined, and the uniformity of budbreak increased.

        Impacts
        (N/A)

        Publications


          Progress 10/01/90 to 09/30/91

          Outputs
          Fruit of `Mohawk' in 1986 and 1988 and `Shoshoni' pecan ?Carya illinoensis (Wangenh.) C. Koch? in 1986 were thinned during early August using a pecan shaker with modified shaker pads. Fruit removed ranged from 44% to 57% of the crop load. Fruit thinning increased nut size of `Mohawk' in both years, but did not affect nut size of `Shoshoni'. Kernel percentage of thinned `Mohawk' and `Shoshoni' trees increased, and kernel grade of `Mohawk' improved relative to unthinned trees. Return bloom of `Mohawk' was not affected either year by thinning, but return bloom on `Shoshoni' was increased by thinning. Mechanical fruit thinning appears to be a useful commercial tool until better thinning methods are available.

          Impacts
          (N/A)

          Publications


            Progress 10/01/89 to 09/30/90

            Outputs
            Four-month old seedlings of pecan (Carya illinoensis (Wangenh) C. Koch) were either not flooded or flooded for 14 days, then transferred to well-drained conditions for 23 days. Water was withheld from one-half of the trees for 6 days, then trees were rewatered, and water was withheld from all trees. Leaf expansion, leaf dry weight, and the number of new leaves that developed were reduced by flooding, but not trunk or root dry weights. Evapotranspiration rates of flooded trees after transfer to well-drained conditions were initially higher than those of unflooded trees, but decreased to rates of control trees after 12 days. Flooding had no effect on photosynthesis after trees had been transferred to well-drained conditions for 23 days. Drought-stressed trees with leaf water potentials as low as -1.93 MPa had lower leaf photosynthetic CO(2) assimilation rate, transpiration, and leaf conductance to CO(2) as compared to well-watered trees. Leaf internal CO(2) concentration was reduced only by the most severe water-stress treatment. Water use rates and relative water content were lower at the permanent wilting point during a second drought stress when trees had been exposed previously to drought stress.

            Impacts
            (N/A)

            Publications


              Progress 10/01/88 to 09/30/89

              Outputs
              Seedling pecan trees (Carya illinoenis (Wangenh) C. Koch) were either not flooded or flooded 14 days, then transferred to well drained conditions for 23 days. Water was withheld from one-half of the trees for 6 days, then trees were rewatered, and water was withheld from all trees. Leaf expansion, leaf dry weight and the number of new leaves that developed were reduced by flooding, but not trunk or root dry weights. Evapotranspiration rates of flooding trees after transfer to well drained conditions were initially higher than unflooded trees, but decreased to rates of control trees after 12 days. Flooding had no effect on leaf gas exchange after trees had been transferred to well drained conditions for 23 days. Drought stressed trees with leaf water potentials as low as -1.93 MPa had lower net CO(2) assimilation rate, transpiration, and leaf conductance to CO(2) compared to well watered trees. Leaf internal CO(2) concentration was reduced only in by the most severe water stress treatment. Water use rates, and the relative water content were lower at the permanent wilting point during a second drought stress when trees had been exposed previously to drought stress.

              Impacts
              (N/A)

              Publications


                Progress 10/01/87 to 09/30/88

                Outputs
                Roots of 53-day-old pecan seedlings (Carya illinoesis (Wangenh.) C. Koch) were either not flooded or flooded by submerging pots to 2 cm above the soil line in containers of water. Leaf gas exchange measurements at 1000 umolsm photosynthetic photon flux, 340 ulliter CO(2), and 27C were made prior to flooding, after 1, 8, or 15 days of flooding, and 7, 14, or 21 days after flooding was terminated. Net CO(2) assimilation rate (A) decreased 56% after 1 day of flooding. Flooding 9 or 15 days did not further depress A. Carbon assimilation of trees that had been flooded for 8 days and then returned to nonflooded soil for 7 days were similar to unflooded trees. In contrast, A of seedlings flooded 15 days did not regain the A of unflooded trees 14 days after flooding terminated. Transpiration rates paralleled A in all treatments. Leaf conductance to CO(2) (g(L)) was positively correlated with A (R = 0.94). However, leaf internal CO concentraion was not decreased by reduced g(L). Water potential and turgor potential of leaves were higher when trees were flooded, but osmotic potential was unaffected.

                Impacts
                (N/A)

                Publications


                  Progress 10/01/86 to 09/30/87

                  Outputs
                  Roots of 53-day-old pecan seedlings (Carya illinoensis (Wangenh.) C. Koch) were either not flooded or flooded by submerging pots to about 2 cm above the soil line in containers of water. Leaf gas exchange measurements at 1000 umol m S photosynthetic photon flux density, 340 ul liter CO(2) and 27c were made prior to flooding, after 1, 8, or 15 days of flooding, and 7, 14, or 21 days after flooding was terminated. Net CO(2) assimilation rate (A) decreased 56% after 1 day flooding. Flooding 8 or 15 days did not further depress A. Carbon assimilation of trees that had been flooded 8 days, then returned to non-flooded soil for 7 days were similar to unflooded trees. In contrast, A of seedlings flooded 15 days did not regain the A of unflooded trees 14 days after flooding terminated. Transpiration rates paralleled A in all treatments. Leaf conductance to CO(2) (g(L) was positively correlated with A (R = 0.94). However, leaf internal CO(2) concentration was not decreased by reduced g(L). Water potential and tugor potential of leaves were higher when trees were flooded, but osmotic potential was unaffected.

                  Impacts
                  (N/A)

                  Publications


                    Progress 10/01/85 to 09/30/86

                    Outputs
                    Vegetative and fruiting shoots were tagged in October 1982 and 1983 on 'Squirrel' 'Stuart', and 'Cape Fear' pecan trees (Carya illinoensis (Wangenh) C. Koch), and flowering was determined the following years. One-year-old shoots were sampled from vegetative and fruiting shoots of each cultivar on 14 Oct. 1982, 9 Feb., 11 Apr., 14 Oct., and 24 Nov. 1983, and 6 Jan. and 17 Apr. 1984 and analyzed for reducing and nonreducing sugars and starch concentrations. Fruiting reduced return bloom of 'Cape Fear' in 1983 and 1984, and 'Stuart' in 1983. Sugar and starch concentrations varied inversely. Sugar concentrations were increased in November, January, and February, and starch concentrations were greatest during October and April. The total carbohydrate concentration in fruiting shoots of each cultivar was greater or equal to that of vegetative shoots in all but one instance. The degree of return fruiting was positively associated with cultivars with early fruit ripening dates.

                    Impacts
                    (N/A)

                    Publications


                      Progress 01/01/85 to 09/30/85

                      Outputs
                      K foliar applications with adjuvants were evaluated on 30-year-old 'Stuart' and 'Western' pecan trees. Three foliar applications of K(2)SO(4) or KNO(3) at 13 g K L did not increase leaf K in July or Sept. or shuck K concentration in Oct. Addition of urea or NH(4)NO(3) with either K(2)SO(4) or KNO(3) did increase leaf K concentrations above the control in some cases. Nut size and kernel percent were not effected by K treatments. The effect of fruiting of return bloom, and its relationship with stored carbohydrates was determined on 3 cultivars on pecans. 'Squirrel' (early), 'Stuart' (mid) and 'Cape Fear' (late) were chosen for differing ripening dates. One-year-old shoots were sampled from vegetative and fruiting shoots of each cultivar on 14 Oct., and 24 Nov., 6 Jan., and 17 April, and analyzed for reducing and non-reducing sugars and starch concentrations. Fruiting reduced return of 'Cape Fear' and 'Stuart', but not 'Squirrel'. Sugar and starch concentrations varied inversely. Sugar concentrations were higher in Nov., and Jan., and starch concentrations were greatest during Oct., and April. The total carbohydrate concentration in fruiting shoots of each cultivar was greater or equal to that of vegetative shoots in all but one case. Carbohydrate concentration in the shoots does not appear to be closely related to the ability to flower.

                      Impacts
                      (N/A)

                      Publications


                        Progress 01/01/84 to 12/30/84

                        Outputs
                        'Garnet' peach trees on 'Lovell' rootstock and rooted 'Garnet' peach cuttlings planted in 1982 were evaluated in standard and meadow orchard culture. Yield per ha. in 1984 was greater using meadow orchard trees spaced .6m by 3m than standard trees spaced from 3m by 6m to 6m by 7.5m. Yield of standard trees decreased as tree spacing increased. A pecan-peach interplanting study was initiated in 1980 using 'Apache' seedlings pecans and either standard 'Redhaven' peach on 'Lovell' rootstock or rooted 'Redhaven' cuttings in meadow orchard culture. Results indicated that interplantings using meadow orchards reduced pecan tree growth more than standard peach trees or no peach trees. Marketable yield was greater from standard meadow orchard culture.

                        Impacts
                        (N/A)

                        Publications


                          Progress 01/01/83 to 12/30/83

                          Outputs
                          N and K were applied 5 consecutive years to 'Western' pecan trees at 0, 56, 112 or 224 kg/ha and 0,93 or 186 kg/ha, respectively. Leaf N concentration, shoot growth, number of new shoots per 1-year-old shoot, and yield increased as N rate increased. K did not affect leaf K concentration, even though trees were low in K, until the 5th year, when a significant increase in leaf K was detected. Other parameters measured were not affected by K applicattion. An experiment was initiated in 1982 to determine the effect of fruit ripening date on return bloom, and the influence of previous fruiting and the leaf/fruit ratio on rerun bloom. 'Squirrel', 'Stuart' and 'Cape Fear' were selected as early, mid and late ripening cultivars. Early fruit ripening increased the survival of fruiting shoots, and increased return bloom by 31% compared to the late ripening cultivar. Shoots that fruited the previous year had less new shoots, smaller flower clusters, shorter shoot growth and a smaller percentage of the new shoots flowering. Fruit drop was not affected by previous fruiting, but fruit loss was substantially different between the 3 cultivars. Flower and fruit loss was 75%, 79% and 53% for 'Squirrel', 'Stuart' and 'Cape Fear', respectively.

                          Impacts
                          (N/A)

                          Publications