Progress 04/01/17 to 09/30/21
Outputs
Target Audience:The targeted audience includes primarily other scientists interested in solving nitrate and phosphorus pollution of Corn Belt waters and greatly reducing soil erosion and resultant sedimentation of waterways. Our results thus far have generated significant interest among a number of scientists and industry personnel in Iowa and surrounding states. Consequently, we are leveraging our preliminary results and have submitted a letter of intent for the Sustainable Agricultural Systems area of the NIFA AFRI program. Changes/Problems:Field research was impacted by the COVID-19 pandemic preventing hiring hourly employees in 2020; we were able to hire an hourly employee in the summer of 2021 to assist with data collection. Field work was carried by a graduate student (objective 1) and a postdoc that joined the project in 2020 (objective 3). A derecho storm that occurred in August caused significant wind damage in some plots, however, other plots were unaffected where perennial groundcover was present, offering empirical evidence of perennial groundcover contributions to soil strength under extreme wind conditions. A controlled environment study was added to complement the field studies conducted under Objectives 1 and 2. Because the fertilizer N treatments did not suppress bluegrass growth as anticipated those treatments were replaced by herbicide and flaming treatments as described under Objective 3 above. What opportunities for training and professional development has the project provided?In 2020, PhD student Allen Chen submitted a poster to the annual ASA-CSSA-SSSA meeting (held virtually, November 2020) titled 'Photothermal Control of Vegetative Dormancy in Poa secunda'. Allen Chen also provided an oral presentation at the annual ASA-CSSA-SSSA meeting (held virtually, November 2020) titled, 'Perennial Ground Covers for Maize Grain and Biomass Production.' In 2020 and 2021, Cynthia Bartel, postdoctoral research associate who joined the project in 2020, assumed responsibilities as planning committee event chair for multiple events, namely field days, Tri-Societies and extension workshops as listed under the presentations list, and conducted field work responsibilities for objective 3. In 2019, Kaitlin Diggins, a former undergraduate intern of the lab, presented initial data and observations of the controlled environment dormancy study in two poster sessions. The first was presented with Lauren Bilek, another undergraduate intern with the lab, as a part of the ISU Honors Program poster session at the end of the spring semester in 2019 (Poster title: Temperature and Daylength Thresholds for Summer Dormancy in Sandberg Bluegrass). The same poster was presented by Kaitlin again with minor revisions at a poster session held by the LSAMP-IINSPIRE program in July 2019. Kaitlin continued assisting the project as a paid worker through the summer and fall semesters, assisting with field work and maintaining the collection of growth chamber data. Allen Chen, PhD student, presented posters on research conducted under objectives 1 and 2 at the Graduate Program in Sustainable Agriculture conference and the annual meeting of Crop Science Society of America. Two First-Year Honors Students, Kaitlin Diggins and Lauren Bilek participated in the controlled environment study. A mini-grant was awarded from ISU's Honors Program to support the students' research. How have the results been disseminated to communities of interest?Bartel, C. A. 2021. Session B4: Look to the Future with a Systems Approach to Achieving Soil and Water Conservation with High-Yield Row Crop Production. Co-presentation with Corteva Agriscience and the Iowa Soybean Association at the Fifth Annual Iowa State University Extension and Outreach Women in Ag Leadership Conference: Lead Like Someone Left the Gate Open. November 30, 2021. ~20 attendees. Moore, K. J., Bartel, C. A., Fei, S., Chen, A. A. & Galland, P. 2021. Iowa State University Biomass Cropping Systems Lab Perennial Groundcover Field Day. Ames, Iowa, May 26, 2021. ~25 attendees. Moore, K. J., Bartel, C. A. 2021. Iowa State University Biomass Cropping Systems Lab Farmer Online Workshop:A Systems Approach to Achieving Soil & Water Conservation with Large-Scale, High-Yield, Row Crop Production. February 15, 2021, online. ~50 attendees. Bartel, C. A. 2020. Iowa Learning Farms extension program, Perennial Groundcovers for Achieving Soil & Water Conservation with Large-Scale, High-Yield, Row Crop Production. Iowa Learning Farms Conservation Webinar Series. Ames, Iowa, December 16, 2020. ~110 attendees. Moore, K. J. 2020. Oral Presentation at the workshop Growing Food Crops with Perennial Groundcover in conjunction with the 2020 International Annual Meetings of the American Society of Agronomy, Crop Science Society of America, and the Soil Science Society of America. November 11, 2020. Bartel, C. A. 2020. Perennial Groundcover: Socioeconomic Implications & Policy Strategy. American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America Annual Meeting Tri-SocietiesGrowing Food Crops with Perennial GroundcoverWorkshop. Invited session panel lead and planning committee event chair. November 11-16, 2020, online. ~75 attendees. Fei, S. 2020. Oral Presentation at the workshop Growing Food Crops with Perennial Groundcover in conjunction with the 2020 International Annual Meetings of the American Society of Agronomy, Crop Science Society of America, and the Soil Science Society of America. Presentation title: Breeding for Perennial Groundcover. November 14, 2020. Moore, K. J., Bartel, C. A., Fei, S., Chen, A. A. & Galland, P. 2020. Iowa State University Biomass Cropping Systems Lab Growing Food Crops with Perennial Groundcover Field Day Presentations. Ames, Iowa, September 4, 2020. ~20 attendees. Chen, A. A. 2019. Poster presentation at the annual ASA-CSSA-SSSA meeting in San Antonio, TX (November 2019). Poster title: Perennial Cover Crop Systems for Maize Grain and Biomass Production. Chen, A. A. 2019. 3rd place Ph.D. poster in Graduate Program in Sustainable Agriculture Colloquium (April 2019). Poster title: Perennial Turfgrass Cover Crops for Midwestern Maize Systems. Fei, S. 2019. Opportunities and Challenges of Genome Editing in Polyploids: A Switchgrass Perspective. R. F. Baker Center for Plant Breeding Symposium, March 1, 2019. Fei, S. 2018. Applications of genome editing in crops. Genome Editing Symposium, the Autonomous University of Nuevo León, Monterrey, Mexico October 23-25, 2018. Fei, S. 2018. Gene editing in polyploid grasses using CRISPR/Cas9. Anhui Agricultural University, Hefei, Anhui Province, China. August 13, 2018. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Objective 1.Screen modern cultivars of turfgrass when grown with corn. A total of 20 cultivars from seven cool-season grass species were established at the Sorensen Research Farm near Ames, IA in the fall of 2017. Visual estimation on a scale of 0-9, with 0 being no grass present and 9 being full coverage, was taken across the entire growing season. In 2018,with the exception of sandberg bluegrass, which scored < 2 during the season, all other species scored at least 6 and coverage increased as the season progressed, suggesting shade resulting from closing maize canopy did not negatively affect grass coverage. Kentucky bluegrass, red and sheep fescues are the top three performers on ground coverage. Kentucky bluegrass affected maize plant height the least among all tested species.In 2019, all grass species with exception to Sandberg bluegrass, western wheatgrass, and intermediate wheatgrass performed similarly to the previous year, with ratings > 6 throughout the season.Overall maize grain yields were much less than the previous year, likely due to extreme rain events experienced throughout the beginning of the growing season that delayed maize planting.In 2020, with the exception of sandberg bluegrass, all groundcovers maintained good to excellent cover throughout the growing season. Sandberg bluegrass expressed greater summer dormancy than the other groundcovers but recovered to a great extent in fall. Grain yields were not statistically different between treatments in 2020 including the control but yields were considerably less than previous years. Individual varieties of kentucky bluegrass (Blue Coat, Camas, and Award) performed better than the no-grass control though the species as a whole did not. However, kentucky bluegrass and sandberg bluegrass both were top performers in 2020, similar to the 2018 season. Objective 2.Identify unique germplasm from the USDA-GRIN. Sandberg bluegrass (Poa secunda) growth chamber studies: Summer dormancy can be a desirable trait for perennial groundcover (PGC) as it can eliminate competitionbetween PGC and the main crop for nutrients and soil moisture. The genus Poa contains several species that exhibit well defined summer dormancy including sandberg bluegrass (P. secunda) and bulbous bluegrass (P. bulbosa). We tested the effects of different combinations of temperature and photoperiod (32.2o C/15 h, 26.6o C/ 14 h, 21.1o C/13 h, and 15.5o C/12 h which represent local field conditions during April, July, September, and October) on summer dormancy induction for P. secunda, and determined the most effective combinations for summer dormancy induction are 32.2o C/15 h and 26.6o C/ 14 h. After 31 days, patterns in cessation of growth were compared over time across each treatment combination. Temperature was found to be a significant factor contributing to cessation of growth (dormancy) while daylength was not (P=0.71). This indicates that temperature is likely more important for controlling dormancy induction. However, when looking at the differences in cessation of growth over time between the 32.2o C/15 hr treatment and 32.2o C/12 hr, it appears daylength may enhance dormancy induction based on both PI232347 and PI639272 reaching full dormancy (a rating of 2 or below) five days earlier in the 32.2o C/15 hr treatment. Objective 3.Evaluating Chemical Treatments to Alter Red/Far Red Light in Perennial Groundcovers Burning & chemical suppression Early exposure to weeds triggers a maize shade avoidance response before or during the critical period for weed control, resulting from a low-red to far-red light ratio shift, impeding maize biomass accumulation and development. An inadequately suppressed perennial groundcover will act as an early-season weed, causing a maize shade avoidance response even with resources abundance.Spring suppresion of kentucky bluegrass with urea ammonium nitrate (UAN) and potassium chloride (KCl) additions was examined in a field study in 2017. Each fertilizer was applied to established grass at four rates. Somewhat contrary to reports in the turfgrass literature, neither urea nor KCl application caused substantial browning of leaves. Leaf burn did occur, particularly on tips and margins following application at the higher rates of urea, 200 and 250 lbs N/acre. However, following UAN application and a rainfall event, grass greenness ratings and red-far red ratios showed that grass competitiveness with corn likely was increased. Consequently, a new field study was developed and initiated in the field in May 2017. Three herbicides were selected for comparison of reducing competitiveness of kentucky bluegrass. Selection was based on two criteria: 1) herbicide is currently labeled for use on corn, and 2) herbicide is documented to require more than one application for causing mortality of kentucky bluegrass. Formulated glufosinate, sethoxydim, and a combination of rimsulfuron and thifensulfuron methyl were applied at four rates to established kentucky bluegrass in the first week of May 2018 and the third week of May in 2017 and 2018. Results were similar among the three application dates. Glufosinate application resulted in substantial yellowing of grass at all application rates, with the greatest yellowing occurring with the highest two rates. Application of sethoxydim and rimsulfuron-thifensulfuron methyl did not result in a change in grass color, but the combination of rimsulfuron-thifensulfuron methyl resulted in a cessation of grass growth and development. However, red-far red ratios for all herbicide treatments were similar to those of the untreated controls. A study was initiated in 2018 comparing timing and intensity of flaming kentucky bluegrass was repeated in 2019. Treatments included flaming aboveground leaves each of the four weeks in May, and flaming for two, three, and four consecutive weeks. General trends included elevated red-far red ratio, which is desirable to preclude the shade avoidance response from corn, in the first collection date after flaming. While a single flaming of bluegrass resulted in elevated red-far red ratio, flaming two and three consecutive weeks provided elevated red-far red ratio for several weeks longer than the single burn date, after which bluegrass initiated green regrowth. Flaming in four consecutive weeks weakened the bluegrass substantially and the red-far red ratio remained elevated for the season. Another filedstudy was conducted in 2020-2121 to assess application timing and groundcover suppressant chemistries on maize growth and development. Two chemical suppression treatments (Gramoxone or Gramoxone+Glufosinate) were applied to a kentucky bluegrass (Poa pratensis L.) 'Midnight' variety groundcover at day of planting (DOP) and each of seven consecutive maize development stages (VE, V1, V2, V3, V4, V5, and V6). We measured weekly for maize plant height, stage, R:RF, early vegetative and final plant density (V2 and R6), as well as grain and stover yield, yield components of kernel rows ear-1, kernels row-1, kernels ear-1, ear length, kernel weight, grain quality, and weed communities. The R:FR increased after suppressant chemistries were applied. While decreased R:FR triggered shade avoidance response and taller maize plants in early vegetative growth stages, final maize plant height was taller in better suppressed treatments. While treatment did not affect plant density, Gramoxone+Glufosinate was more effective at suppression in the post-establishment year, and yielded 8% more maize grain than Gramoxone alone across treatments in yr 1, as well as 11% greater stover and 5% greater TAB in yr 2.
Publications
- Type:
Journal Articles
Status:
Under Review
Year Published:
2022
Citation:
Chen, A. A., Fei, S., Lenssen, A. W. & Moore, K. J. (202_). Evaluating cool-season grass species as potential perennial groundcover for maize production. Submitted to Agronomy Journal. In revision.
- Type:
Journal Articles
Status:
Under Review
Year Published:
2022
Citation:
Chen, A. A., Fei, S., Lenssen, A. W. & Moore, K. J. (202_). Evaluating commercial cool-season turfgrasses as perennial groundcover in intercropped maize. In preparation.
- Type:
Journal Articles
Status:
Under Review
Year Published:
2022
Citation:
Chen, A. A., Fei, S., Lenssen, A. W. & Moore, K. J. Photothermal controls of vegetative dormancy in Poa secunda. In preparation.
- Type:
Journal Articles
Status:
Under Review
Year Published:
2022
Citation:
Bartel, C. A., Moore, K. J., Fei, S., Lenssen, A. W., Hintz, R. L. & Kling, S. M. (202_). Evaluating chemical treatments to alter red:far red in perennial groundcovers. In preparation.
- Type:
Journal Articles
Status:
Under Review
Year Published:
2022
Citation:
Bartel, C. A., Moore, K. J., Fei, S., Lenssen, A. W., Hintz, R. L. & Kling, S. M. (202_). Evaluating strip and no-till establishment and maintenance of perennial groundcovers. In preparation.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2020
Citation:
Moore, K. J. 2020. Oral Presentation at the workshop Growing Food Crops with Perennial Groundcover in conjunction with the 2020 International Annual Meetings of the American Society of Agronomy, Crop Science Society of America, and the Soil Science Society of America. November 11, 2020.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2020
Citation:
Bartel, C. A. 2020. Perennial Groundcover: Socioeconomic Implications & Policy Strategy. American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America Annual Meeting Tri-Societies Growing Food Crops with Perennial Groundcover Workshop. Invited session panel lead and planning committee event chair. November 11-16, 2020,
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2020
Citation:
Fei, S. 2020. Oral Presentation at the workshop Growing Food Crops with Perennial Groundcover in conjunction with the 2020 International Annual Meetings of the American Society of Agronomy, Crop Science Society of America, and the Soil Science Society of America. Presentation title: Breeding for Perennial Groundcover. November 14, 2020.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2019
Citation:
Chen, A. A. 2019. Poster presentation at the annual ASA-CSSA-SSSA meeting in San Antonio, TX (November 2019). Poster title: Perennial Cover Crop Systems for Maize Grain and Biomass Production.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2018
Citation:
Fei, S. 2018. Applications of genome editing in crops. Genome Editing Symposium, the Autonomous University of Nuevo Le�n, Monterrey, Mexico October 23-25, 2018.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2018
Citation:
Fei, S. 2018. Gene editing in polyploid grasses using CRISPR/Cas9. Anhui Agricultural University, Hefei, Anhui Province, China. August 13, 2018.
- Type:
Theses/Dissertations
Status:
Awaiting Publication
Year Published:
2022
Citation:
Allen A. Chen. 2022. Evaluating cool-season turfgrasses as potential perennial groundcover for maize production systems. Ph.D. Dissertation. Iowa State University, Ames, IA.
|
Progress 04/01/20 to 03/31/21
Outputs
Target Audience:The targeted audience includes primarily other scientists interested in solving nitrate and phosphorus pollution of Corn Belt waters and greatly reducing soil erosion and resultant sedimentation of waterways. Our results thus far have generated significant interest among a number of scientists and industry personnel in Iowa and surrounding states. Consequently, we are leveraging our preliminary results and have submitted a letter of intent for the Sustainable Agricultural Systems area of the NIFA AFRI program. Changes/Problems:Field research was impacted by the COVID-19 pandemic preventing hiring hourly employees. However, field work was carried by a graduate student (objective 1) and a postdoc that joined the project in 2020 (objective 3). A derecho storm that occurred in August caused significant wind damage in some plots. What opportunities for training and professional development has the project provided?Allen Chen - Poster submission to the annual ASA-CSSA-SSSA meeting (held virtually, November 2020). Poster title: Photothermal Control of Vegetative Dormancy in Poa secunda. Allen Chen - Oral presentation at the annual ASA-CSSA-SSSA meeting (held virtually, November 2020). Presentation title: Perennial Ground Covers for Maize Grain and Biomass Production. How have the results been disseminated to communities of interest?Fei, S. Oral Presentation at the workshop Growing Food Crops with Perennial Groundcover in conjunction with the 2020 International Annual Meetings of the American Society of Agronomy, Crop Science Society of America, and the Soil Science Society of America. Presentation title: Breeding for Perennial Groundcover. November 14, 2020 Fei S, Chen A and Galland P. Field Day presentation: Growing Food Crops with Perennial Groundcover. September 4, 2020. What do you plan to do during the next reporting period to accomplish the goals?All field research for the initial objectives have been concluded. Manuscript preparation for objective 2 will be completed soon and the submission process should begin shortly. Manuscript preparation for objective 1 and for the P. secunda growth chamber studies will begin once the objective 2 manuscript has been submitted. Data from objective three are being analyzed and a journal article reporting the results will be prepared. Follow-up studies described herein will be repeated a second year in 2021.
Impacts
What was accomplished under these goals?
Objective 1. Screen modern cultivars of turfgrass when grown with corn. A total of 20 cultivars from seven cool-season grass species were established at the Sorensen Research Farm near Ames, IA in the fall of 2017. The third and final data set was collected from this field in 2020. Visual estimation on a scale of 0-9, with 0 being no grass present and 9 being full coverage, was taken across the entire growing season. With the exception of sandberg bluegrass, all groundcovers maintained good to excellent cover throughout the growing season. Sandberg bluegrass expressed higher summer dormancy than the other groundcovers but recovered to a great extent in fall. Grain yields were not statistically different between treatments in 2020 including the control but yields were considerably lower than previous years, likely due to severe damage caused by a derecho in August 2020. Individual varieties of kentucky bluegrass (Blue Coat, Camas, and Award) performed better than the no-grass control though the species as a whole did not. However, kentucky bluegrass and sandberg bluegrass both were top performers in 2020, similar to the 2018 season. Kentucky bluegrass remains a species of interest as a result of this year's data and is the subject of further investigation with grant support provided by the Iowa Nutrient Research Center Objective 2. Identify unique germplasm from the USDA-GRIN. Data collection on the objective 2 field concluded in the 2019 season. Sandberg bluegrass (Poa secunda) growth chamber studies: Summer dormancy is a desirable trait for perennial groundcover. A dormancy induction study involving three accessions of P. secunda (PI232347, PI232348, and PI639272) and "Audubon " red fescue as a control was conducted and concluded by late 2019. Four temperature and day length combinations, 32.2oC/15hr, 26.6oC/14hr, 21.1oC/13hr, and 15.5oC/12hr, were used as treatments for the study. Based on the findings of the dormancy induction experiment, a new experiment investigating conditions that break dormancy in P. secunda was conducted in 2020 using the same treatments. The same three P. secunda accessions were first induced to complete dormancy in a 32.2oC/15hr chamber for three weeks, after which they are moved to chambers with treatments of 26.6oC/14hr, 21.1oC/13hr, or 15.5oC/12hr until dormancy was broken. After three weeks, PI639272 was most responsive to the treatments, with 86% of plants resuming growth in the 15.5oC/12hr treatment, 76% in the 21.1oC/13hr treatment, and 26% in the 26.6oC/14hr treatment. Eighty percent of PI232347 plants resumed growth in the 15.5oC/12hr treatment, 20% in the 21.1oC/13hr treatment, and 3% in the 26.6oC/14hr treatment. PI232348 had a similar response to the 26.6oC/14hr treatment, with only 7% of plants resuming growth, but responded better than PI232347 to the 15.5oC/12hr and 21.1oC/13hr treatments, with 90% and 60% of plants resuming growth, respectively. Objective 3. In 2020, two different herbicide treatments (Gramoxone or Gramoxone + Glufosinate) were applied to kentucky bluegrass 'Midnight' groundcover (seeded in fall 2019) at day of maize planting and each of five consecutive maize development stages (VE, V2, V3, V4, V5, and V6). Precipitation and wind in yr 1 prevented the V1 application; untreated plots were added as controls. Maize height, stage, and R/RF were measured weekly, with V2 and R6 maize plant density and end-of-season stover yield. Grain yield, row ear and kernel # ear (yield components), and grain quality are being measured this winter. Maize plant height for the control was greater than the maize in the suppression treatments, but this trend reversed at V5. During the first two maize plant height collection dates, increased maize plant height corresponded with lesser R/FR readings; however, as the maize matured, the maize in treatments with greater R/FR attained a greater final plant height. Faster maturing maize was observed in PGC with earlier chemical applications vs. the control. Three suppression methods on kentucky bluegrass 'Midnight' groundcover (seeded in fall 2019), inc. ETS tillage, Unverferth tillage, and Redball hooded band sprayer, each at two widths of 10" and 15" (with band sprayer at 20") were assessed on maize growth and development. Alternate groundcover strips at 10" and 15", as well as three non-PGC controls (conventional tillage, ETS tillage at 10", and no till), were also assessed. Maize height, stage, and R/RF were measured weekly, with V2 and R6 maize plant density and end-of-season stover yield. Grain yield, row ear and kernel # ear (yield components), and grain quality are being measured this winter. Maize plant density was similar among treatments at V2 and R6. Maize maturity within the PGC suppression lagged conventional maize during the early vegetative stages. Maize plant height was generally similar for the 10" and 15-20" suppression widths, similar for alternating PGC strips and conventional tillage, and greater for alternating PGC strips than in continual PGC rows, starting at ~June 24. Maize plant height was similar for continual PGC and non-PGC treatments.
Publications
|
Progress 04/01/19 to 03/31/20
Outputs
Target Audience:The targeted audience includes primarily other scientists interested in solving nitrate and phosphorus pollution of Corn Belt waters and greatly reducing soil erosion and resultant sedimentation of waterways. Our results thus far have generated significant interest among a number of scientists and industry personnel in Iowa and surrounding states. Consequently, we are leveraging our preliminary results and have submitted a letter of intent for the Sustainable Agricultural Systems area of the NIFA AFRI program. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Kaitlin Diggins, a former undergraduate intern of the lab, presented initial data and observations of the controlled environment dormancy study in two poster sessions. The first was presented with Lauren Bilek, another undergraduate intern with the lab, as a part of the ISU Honors Program poster session at the end of the spring semester in 2019 (Poster title: Temperature and Daylength Thresholds for Summer Dormancy in Sandberg Bluegrass). The same poster was presented by Kaitlin again with minor revisions at a poster session held by the LSAMP-IINSPIRE program in July 2019. Kaitlin continued assisting the project as a paid worker through the summer and fall semesters, assisting with field work and maintaining the collection of growth chamber data. How have the results been disseminated to communities of interest?Allen Chen - 3rd place Ph.D. poster in Graduate Program in Sustainable Agriculture Colloquium (April 2019). Poster title: Perennial Turfgrass Cover Crops for Midwestern Maize Systems. Allen Chen - Poster presentation at the annual ASA-CSSA-SSSA meeting in San Antonio, TX (November 2019). Poster title: Perennial Cover Crop Systems for Maize Grain and Biomass Production. What do you plan to do during the next reporting period to accomplish the goals?The last complete set of data will be collected in 2020 for Objective 1, after which manuscript preparation will begin. The results from Objective 2 are already in preparation for publication. The remainder of the dormancy breakage studies will continue, after which results will be combined with the dormancy induction experiment to produce a manuscript as well. A field trial was established on September 7, 2019 for the project funded by Iowa Nutrient Research Center. This project aims to investigate the above and below-ground nutrient dynamics and the potential of using perennial ground cover (PGC) to reduce non-point nitrogen and phosphorus pollution in the next couple of years. Data from objective three are being analyzed and a journal article reporting the results will be prepared.
Impacts
What was accomplished under these goals?
Objective 1. Screen modern cultivars of turfgrass when grown with corn. A total of 20 cultivars from seven cool-season grass species were established at the Sorensen Research Farm near Ames, IA in the fall of 2017. A second set of data was collected for the same field used for objective 1 in 2019. Visual estimation on a scale of 0-9, with 0 being no grass present and 9 being full coverage, was taken across the growing season. All grass species with exception to Sandberg bluegrass, western wheatgrass, and intermediate wheatgrass performed similarly to the previous year, with ratings above 6 throughout the season. Sandberg bluegrass, despite having low ratings the previous year, increased its coverage considerably in the 2019 season. Western and intermediate wheatgrass suffered wheel traffic damage early in the season, wiping out approximately half of the coverage gained the previous year. All grass treatments affected corn heights negatively, though differences in effect across treatments was minimal with exception of Sandberg bluegrass. Corn heights are presented in the graph below. Overall maize grain yields were much lower than the previous year, likely due to extreme rain events experienced throughout the beginning of the growing season that delayed maize planting. Plots planted with Rush (intermediate wheatgrass) and Arriba (western wheatgrass) were ranked highly in grain yield. This is likely due to decreased competition as a result of reduced ground coverage. Aside from these two cultivars, tall and sheep fescues dominate the top performers, though only Summer and JT-783 were statistically similar to the no-grass control. Objective 2. Identify unique germplasm from the USDA-GRIN. Twenty wild or unimproved accessions each for Kentucky bluegrass, red fescue, and Sandburg bluegrass were space-planted in spring 2017. Two years of data were already taken for 2017 and 2018 when these perennial ground covers were co-grown with maize. This is the third year of the project. Field plots for this research objective were unfortunately severely hindered by extreme weed pressure, partially a result of the inaccessibility of fields after severe rain events. Maize plant heights were not taken due to the extreme variability among and within replications. However, grass spread was still measured on a visual scale (0-9), with 0 being no grass present and 9 being full coverage. Kentucky bluegrass and red fescue performed similarly to last year, with Kentucky bluegrass experiencing an initial increase in spread followed by a decline then resurgence in the fall and red fescue remaining relatively stable throughout the entire season. Sandberg bluegrass performance varied greatly, but the vast majority maintained average spreads of a rating of 4 or below throughout the season, remaining fairly uncompetitive. The difference in performance can also be seen affecting grain yield, with plots of Kentucky bluegrass and red fescue yielding considerably lower than the no-grass control, but plots of Sandberg bluegrass yielding more than the no-grass control. P. secunda dormancy growth chamber study. A controlled environment study was done to determine the environment conditions that induce summer dormancy in sandberg bluegrass. Dormancy induction studies involving three accessions of Sandberg bluegrass (PI232347, PI232348, and PI639272) and "Audubon" red fescue as a control were conducted and concluded by late 2019. Four temperature and day length combinations, 32.2C/15hr, 26.6C/14hr, 21.1C/13hr, and 15.5C/12hr, were used as treatments for the study. Onset of dormancy was considered to be when 50% or more of the green tissue had senesced in a pot (corresponding with a visual rating of 5 or below). Onset of dormancy varied with accessions but began as early as about two weeks into treatment for the 32.2C/15hr combination. There appear to be accession and treatment interactions because PI232347 and PI232348 respond similarly to each of the different treatments whereas PI639272 behaves slightly differently. The 32.2C/15hr and 26.6C/14hr treatments both induced dormancy in PI232347 and PI 232348. 50% of plants exhibited dormancy behaviors around two weeks and full dormancy was reached around three weeks in the 32.2C/15hr treatment. In contrast, the next highest treatment, 26.6C/14hr, induced dormancy much later around four weeks. In both PI232347 and PI232348, it took twice as long for the same amount of material to exhibit dormancy behaviors in the 26.6C/14hr treatment as the 32.2C/15hr treatment. This suggests that intensity of temperature and daylength may have temporal effects on dormancy induction. 21.1C/13hr and 15.5C/12hr treatments did not induce dormancy in either PI232347 or PI232348. In agreement with our initial observations in early 2019, every treatment combination induced dormancy in PI639272 with exception of the 15.5C/12hr treatment. Response to treatments seemed more evenly spread out, with the amount of dormant material increasing rapidly in the 32.2C/15hr treatment, slowly but steadily increasing in the 26.6C/14hr treatment, and remaining constant in the 21.1C/13hr treatment. This suggests that dormancy induction in PI639272 may be more sensitive to smaller changes in temperature and daylength when compared to PI232347 and PI232348. The non-dormant red fescue control behaved as expected, with little change over the entire experiment and no dormancy observed. An experiment investigating conditions that break dormancy in Poa secunda is ongoing. The same three Poa secunda accessions were first induced to dormancy in a 32.2C/15hr chamber for three weeks, after which they are moved to chambers with treatments of 26.6C/14hr, 21.1C/13hr, or 15.5C/12hr until dormancy was broken. This experiment will be replicated three times, after which results of both dormancy induction and breakage will be disseminated in the form of a journal article. Preliminary results from the first replication indicate that the 15.5C/12hr treatment breaks dormancy more rapidly and in more numbers than the 21.1C/13hr treatment. The 26.6C/14hr treatment did not break dormancy in plants in the first replication of the experiment. Field observation of bulbous bluegrass study. To broaden the candidate species pool for perennial groundcover, on September 12, 2018 we initiated a field observational study on dormancy response of Poa bulbosa in central Iowa in collaboration with Radix Research Inc. (Junction City, OR). Seeds of four experimental lines of PB 55, 333, 344 and 350 were established in 1'x12' strips with four replications at Sorenson Farm, located in Boone, IA. Establishment was conducted by broadcast seeding by hand within the designated plot area and plots were irrigated daily as needed until early October of 2018. Poa bulbosa growth persisted well into May, but began to decline with increasing weed pressure and high temperatures, longer photoperiod or both and by June 24, 2019, all plots of Poa bulbosa went complete dormancy. After a week of rain fall in early September, 2019, however all plots of Poa bulbosa broke dormancy and resumed vigorous growth. Objective 3. The flaming study initiated in 2018 comparing timing and intensity of flaming kentucky bluegrass was repeated in 2019. Treatments included flaming aboveground leaves each of the four weeks in May, and flaming for two, three, and four consecutive weeks. A single flaming of bluegrass resulted in elevated red-far red ratio, which is desirable to preclude the shade avoidance response from corn. Flaming two and three consecutive weeks provided elevated red-far red ratio for at least 4 weeks, after which bluegrass initiated green regrowth. Flaming in four consecutive weeks weakened the bluegrass substantially. We will evaluate red-far red ratio and greenness index from the flaming experiments until spring to determine if burning treatments have long-term effects on red-far red ratio and greenness index.
Publications
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Progress 04/01/19 to 02/29/20
Outputs
Target Audience:The targeted audience includes primarily other scientists interested in solving nitrate and phosphorus pollution of Corn Belt waters and greatly reducing soil erosion and resultant sedimentation of waterways. Our results thus far have generated significant interest among a number of scientists and industry personnel in Iowa and surrounding states. Consequently, we are leveraging our preliminary results and have submitted a letter of intent for the Sustainable Agricultural Systems area of the NIFA AFRI program. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Kaitlin Diggins, a former undergraduate intern of the lab, presented initial data and observations of the controlled environment dormancy study in two poster sessions. The first was presented with Lauren Bilek, another undergraduate intern with the lab, as a part of the ISU Honors Program poster session at the end of the spring semester in 2019 (Poster title: Temperature and Daylength Thresholds for Summer Dormancy in Sandberg Bluegrass). The same poster was presented by Kaitlin again with minor revisions at a poster session held by the LSAMP-IINSPIRE program in July 2019. Kaitlin continued assisting the project as a paid worker through the summer and fall semesters, assisting with field work and maintaining the collection of growth chamber data. How have the results been disseminated to communities of interest?Allen Chen - 3rd place Ph.D. poster in Graduate Program in Sustainable Agriculture Colloquium (April 2019). Poster title: Perennial Turfgrass Cover Crops for Midwestern Maize Systems. Allen Chen - Poster presentation at the annual ASA-CSSA-SSSA meeting in San Antonio, TX (November 2019). Poster title: Perennial Cover Crop Systems for Maize Grain and Biomass Production. What do you plan to do during the next reporting period to accomplish the goals?The last complete set of data will be collected in 2020 for Objective 1, after which manuscript preparation will begin. The results from Objective 2 are already in preparation for publication. The remainder of the dormancy breakage studies will continue, after which results will be combined with the dormancy induction experiment to produce a manuscript as well. A field trial was established on September 7, 2019 for the project funded by Iowa Nutrient Research Center. This project aims to investigate the above and below-ground nutrient dynamics and the potential of using perennial ground cover (PGC) to reduce non-point nitrogen and phosphorus pollution in the next couple of years. Data from objective three are being analyzed and a journal article reporting the results will be prepared.
Impacts
What was accomplished under these goals?
Objective 1. Screen modern cultivars of turfgrass when grown with corn. A total of 20 cultivars from seven cool-season grass species were established at the Sorensen Research Farm near Ames, IA in the fall of 2017. A second set of data was collected for the same field used for objective 1 in 2019. Visual estimation on a scale of 0-9, with 0 being no grass present and 9 being full coverage, was taken across the growing season. All grass species with exception to Sandberg bluegrass, western wheatgrass, and intermediate wheatgrass performed similarly to the previous year, with ratings above 6 throughout the season. Sandberg bluegrass, despite having low ratings the previous year, increased its coverage considerably in the 2019 season. Western and intermediate wheatgrass suffered wheel traffic damage early in the season, wiping out approximately half of the coverage gained the previous year. All grass treatments affected corn heights negatively, though differences in effect across treatments was minimal with exception of Sandberg bluegrass. Corn heights are presented in the graph below. Overall maize grain yields were much lower than the previous year, likely due to extreme rain events experienced throughout the beginning of the growing season that delayed maize planting. Plots planted with Rush (intermediate wheatgrass) and Arriba (western wheatgrass) were ranked highly in grain yield. This is likely due to decreased competition as a result of reduced ground coverage. Aside from these two cultivars, tall and sheep fescues dominate the top performers, though only Summer and JT-783 were statistically similar to the no-grass control. Objective 2. Identify unique germplasm from the USDA-GRIN. Twenty wild or unimproved accessions each for Kentucky bluegrass, red fescue, and Sandburg bluegrass were space-planted in spring 2017. Two years of data were already taken for 2017 and 2018 when these perennial ground covers were co-grown with maize. This is the third year of the project. Field plots for this research objective were unfortunately severely hindered by extreme weed pressure, partially a result of the inaccessibility of fields after severe rain events. Maize plant heights were not taken due to the extreme variability among and within replications. However, grass spread was still measured on a visual scale (0-9), with 0 being no grass present and 9 being full coverage. Kentucky bluegrass and red fescue performed similarly to last year, with Kentucky bluegrass experiencing an initial increase in spread followed by a decline then resurgence in the fall and red fescue remaining relatively stable throughout the entire season. Sandberg bluegrass performance varied greatly, but the vast majority maintained average spreads of a rating of 4 or below throughout the season, remaining fairly uncompetitive. The difference in performance can also be seen affecting grain yield, with plots of Kentucky bluegrass and red fescue yielding considerably lower than the no-grass control, but plots of Sandberg bluegrass yielding more than the no-grass control. P. secunda dormancy growth chamber study. A controlled environment study was done to determine the environment conditions that induce summer dormancy in sandberg bluegrass. Dormancy induction studies involving three accessions of Sandberg bluegrass (PI232347, PI232348, and PI639272) and "Audubon" red fescue as a control were conducted and concluded by late 2019. Four temperature and day length combinations, 32.2C/15hr, 26.6C/14hr, 21.1C/13hr, and 15.5C/12hr, were used as treatments for the study. Onset of dormancy was considered to be when 50% or more of the green tissue had senesced in a pot (corresponding with a visual rating of 5 or below). Onset of dormancy varied with accessions but began as early as about two weeks into treatment for the 32.2C/15hr combination. There appear to be accession and treatment interactions because PI232347 and PI232348 respond similarly to each of the different treatments whereas PI639272 behaves slightly differently. The 32.2C/15hr and 26.6C/14hr treatments both induced dormancy in PI232347 and PI 232348. 50% of plants exhibited dormancy behaviors around two weeks and full dormancy was reached around three weeks in the 32.2C/15hr treatment. In contrast, the next highest treatment, 26.6C/14hr, induced dormancy much later around four weeks. In both PI232347 and PI232348, it took twice as long for the same amount of material to exhibit dormancy behaviors in the 26.6C/14hr treatment as the 32.2C/15hr treatment. This suggests that intensity of temperature and daylength may have temporal effects on dormancy induction. 21.1C/13hr and 15.5C/12hr treatments did not induce dormancy in either PI232347 or PI232348. In agreement with our initial observations in early 2019, every treatment combination induced dormancy in PI639272 with exception of the 15.5C/12hr treatment. Response to treatments seemed more evenly spread out, with the amount of dormant material increasing rapidly in the 32.2C/15hr treatment, slowly but steadily increasing in the 26.6C/14hr treatment, and remaining constant in the 21.1C/13hr treatment. This suggests that dormancy induction in PI639272 may be more sensitive to smaller changes in temperature and daylength when compared to PI232347 and PI232348. The non-dormant red fescue control behaved as expected, with little change over the entire experiment and no dormancy observed. An experiment investigating conditions that break dormancy in Poa secunda is ongoing. The same three Poa secunda accessions were first induced to dormancy in a 32.2C/15hr chamber for three weeks, after which they are moved to chambers with treatments of 26.6C/14hr, 21.1C/13hr, or 15.5C/12hr until dormancy was broken. This experiment will be replicated three times, after which results of both dormancy induction and breakage will be disseminated in the form of a journal article. Preliminary results from the first replication indicate that the 15.5C/12hr treatment breaks dormancy more rapidly and in more numbers than the 21.1C/13hr treatment. The 26.6C/14hr treatment did not break dormancy in plants in the first replication of the experiment. Field observation of bulbous bluegrass study. To broaden the candidate species pool for perennial groundcover, on September 12, 2018 we initiated a field observational study on dormancy response of Poa bulbosa in central Iowa in collaboration with Radix Research Inc. (Junction City, OR). Seeds of four experimental lines of PB 55, 333, 344 and 350 were established in 1'x12' strips with four replications at Sorenson Farm, located in Boone, IA. Establishment was conducted by broadcast seeding by hand within the designated plot area and plots were irrigated daily as needed until early October of 2018. Poa bulbosa growth persisted well into May, but began to decline with increasing weed pressure and high temperatures, longer photoperiod or both and by June 24, 2019, all plots of Poa bulbosa went complete dormancy. After a week of rain fall in early September, 2019, however all plots of Poa bulbosa broke dormancy and resumed vigorous growth. Objective 3. The flaming study initiated in 2018 comparing timing and intensity of flaming kentucky bluegrass was repeated in 2019. Treatments included flaming aboveground leaves each of the four weeks in May, and flaming for two, three, and four consecutive weeks. A single flaming of bluegrass resulted in elevated red-far red ratio, which is desirable to preclude the shade avoidance response from corn. Flaming two and three consecutive weeks provided elevated red-far red ratio for at least 4 weeks, after which bluegrass initiated green regrowth. Flaming in four consecutive weeks weakened the bluegrass substantially. We will evaluate red-far red ratio and greenness index from the flaming experiments until spring to determine if burning treatments have long-term effects on red-far red ratio and greenness index.
Publications
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Progress 04/01/18 to 03/31/19
Outputs
Target Audience:At this time, the targeted audience includes primarily other scientists interested in solving nitrate and phosphorus pollution of Corn Belt waters and greatly reducing soil erosion and resultant sedimentation of waterways. Our results thus far have generated significant interest among a number of scientists and industry personnel in Iowa and surrounding states. Consequently, we are leveraging our preliminary results and have submitted a letter of intent for the Sustainable Agricultural Systems area of the NIFA AFRI program. Changes/Problems:A controlled environment study was added to complement the field studies conducted under Objectives 1 and 2. Because the fertilizer N treatments did not suppress bluegrass growth as anticipated those treatments were replaced by herbicide and flaming treatments as described under Objective 3 above. What opportunities for training and professional development has the project provided?Allen Chen, 2nd year Ph.D. student is making good progress. He will be presenting posters on research conducted under objectives 1 and 2 at the upcoming Graduate Program in Sustainable Agriculture conference as well as at the annual meeting of Crop Science Society of America in November. Two First-Year Honors Students, Kaitlin Diggins and Lauren Bilek are participating in the controlled environment study. A mini-grant was awarded from ISU's Honors Program to support the students' research. Kaitlin Diggins was scheduled to make a presentation on her research at the Society for Advancement of Chicanos/Hispanics and Native Americans in Science (SACNAS) this November in Honolulu, HI. How have the results been disseminated to communities of interest?Co-PD Fei made four presentations in which results of the perennial groundcover project were presented and considerable interest was expressed by the audiences: Increased tiller production in switchgrass by targeted mutagenesis of theteosinte branched 1genes with CRISPR/Cas9. Chinese Academy of Tropical Agricultural Sciences, Haikou, Hainan Province, China. August 8, 2018. Gene editing in polyploid grasses using CRISPR/Cas9. Anhui Agricultural University, Hefei, Anhui Province, China. August 13, 2018. Applications of genome editing in crops. Genome Editing Symposium, the Autonomous University of Nuevo León,Monterrey, MexicoOct 23-25, 2018. Opportunities and Challenges of Genome Editing in Polyploids: A Switchgrass Perspective. R. F. Baker Center for Plant Breeding Symposium, March 1, 2019. What do you plan to do during the next reporting period to accomplish the goals?The field studies described above underObjectives 1 and 2 will be repeated in 2019 to generate more robust results. The controlled environment study will also be repeated as well and will include additional treatments to determine the environmental conditions that break dormancy in sandberg bluegrass.The herbicide and flaming experiments described under Objective 3 will be repeated in 2019.
Impacts
What was accomplished under these goals?
Objective 1. Screen modern cultivars of turfgrass when grown with corn. A total of 20 cultivars from seven cool-season grass species were established at the Sorensen Research Farm near Ames, IA in the fall of 2017. The firstcomplete set of data were taken for Objective 1 on a fully established perennial ground cover in 2018. Visual estimation on a scale of 0-9, with 0 being no grass present and 9 being full coverage was taken to measure the grass coverage during the entire growing season. With the exception of sandberg bluegrass, which scored below 2 or lower during the season, all other species scored at least 6 and coverage increased as the season progressed, suggesting shade resulting from closing maize canopy did not negatively affect grass coverage. Kentucky bluegrass, red and sheep fescues are the top three performers on ground coverage. Kentucky bluegrassaffected maize plant height the least among all tested species. On grain yield, the top three grass species that resulted in the highest grain yield were sandberg bluegrass, kentucky bluegrass and western wheatgrass. There is a large variation among Kentucky bluegrass cultivars on their impact on maize grain yield. Maize grain yield from the best-performing Kentucky bluegrass cultivar, A05-319 is better than the average yield of the control. This reflects the large amount of variation observed in growth habit of the select kentucky bluegrass ciltivars. Objective 2. Identify unique germplasm from the USDA-GRIN. Twenty wild or unimproved accessions each for kentucky bluegrass, red fescue, and sandberg bluegrass were interplanted with maize in spring2017 and overwintered. The second year of complete data were taken for all plots in 2018. On ground coverage, sandberg bluegrass had consistently low coverage (~1). Ground coverage for red fescue began with about 3.5 and increased until late July and early August when it started to decline gradually. Kentucky bluegrass began with a rating of slightly below 3 and increased until early May followed by a steady decline. Maize plants grown with either kentucky bluegrass or red fescue were shorter than those on the non-grass control plots while maize plants grown on plots with sandberg bluegrass as ground cover had negligible effect on maize plant height. On grain yield, red fescue, on average reduced yield while kentucky bluegrass and sandberg bluegrass produced comparable grain yield with that from the non-grass control. P. secunda dormancy growth chamber study. A controlled environment study was done to determine the environmental conditions that induce summer dormancy in sandberg bluegrass. Four temperature and day length combinations, 32.2 C/15 hr, 26.6 C/14 hr, 21.1 C/13 hr, and 15.5 C/12 hr were used for the study. Three sandberg bluegrass accessions, PI232347, PI639272, and PI232348, were evaluated. 'Audubon' red fescue was grown as a non-dormant control. Growth and decline of the grasses were measured by a greenness rating and overall plant height on a daily basis. With the exception of the 15.5 C/12h, all treatments triggereddormancy in all sandberg bluegrass accessions, although the onset time of the dormancy varied among the three accessions. No dormancy was observed for the Audubon red fescue. It was also shown that increased temperature/day length triggered rhizome development in red fescue. Objective 3. Spring suppresion of kentucky bluegrass with urea ammonium nitrate (UAN) and potassium chloride (KCl) additions was examined in a field study in April 2017.Each fertilizer was applied to established grass at four rates. Somewhat contrary to reports in the turfgrass literature, neither urea nor KCl application caused substantial browning of leaves. Leaf burn did occur, particularly on tips and margins following application at the higher rates of urea, 200 and 250 lbs N/acre. However, following UAN application and a rainfall event, grass greenness ratings and red-far red ratios showed that grass competitiveness with corn likely was increased. Consequently, a new field study was developed and initiated in the field in May 2017. Three herbicides were selected for comparison of reducing competitiveness of kentucky bluegrass. Selection was based on two criteria: 1) herbicide is currently labeled for use on corn, and 2) herbicide is documented to require more than one application for causing mortality of kentucky bluegrass. Formulated glufosinate, sethoxydim, and a combination of rimsulfuron and thifensulfuron methyl were applied at four rates to established kentucky bluegrass in the first week of May 2018 and the third week of May in 2017 and 2018. Results were similar among the three application dates. Glufosinate application resulted in substantial yellowing of grass at all application rates, with the greatest yellowing occurring with the highest two rates. Application of sethoxydim and rimsulfuron-thifensulfuron methyl did not result in a change in grass color, but the combination of rimsulfuron-thifensulfuron methyl resulted in a cessation of grass growth and development. However, red-far red ratios for all herbicide treatments were similar to those of the untreated controls. None of the herbicides applied at any rate in 2017 resulted in mortality or loss of grass stand, and thus are suitable in corn-bluegrass weed management systems. A new study was initiated in 2018 comparing timing and intensity of flaming kentucky bluegrass.Treatments included flaming aboveground leaves each of the four weeks in May, and flaming for two, three, and four consecutive weeks.A single flaming of bluegrass resulted in elevated red-far red ratio, which is desirable to preclude the shade avoidance response from corn.Flaming two and three consecutive weeks provided elevated red-far red ratio for at least 4 weeks, after which bluegrass initiated green regrowth. At the time of writing this annual report, flaming in four consecutive weeks appears to have weakened the bluegrass substantially. Regrowth has initiated in the four-times-burned plots but it is patchy. We will continue to monitor red-far red ratio and greenness index from the herbicide and flaming experiments until all plots have substantial regrowth providing data similar to the untreated controls.
Publications
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Progress 04/01/17 to 03/31/18
Outputs
Target Audience:At this time, the targeted audience includes primarily other scientists interested in solving nitrate and phosphorus pollution of Corn Belt waters and greatly reducing soil erosion and resultant sedimentation of waterways. Our results to this time have excited a number of scientists and industry personnel in Iowa and surrounding states. Consequently, we are leveraging our preliminary results and have submitted a letter of intent for the Sustainable Agricultural Systems area ofthe NIFA AFRI program. Changes/Problems:In Objective 2, 2-3 plots (seeded to different accessions) on the south end of the experimental field were planted into an area that was previously an actively growing soybean field. It was tilled fresh to accommodate additional accessions. Because the soil moisture was relatively high when tillage was done, wheel tracks were visible and the field was not very even. Grass seed are small and when they are in recessed areas such as wheel tracks, emergence becomes a problem. This may lead to bias in evaluating the affected accessions. We plan to overseed these plots in the fall of 2018 to correct the problem. As noted above, application of UAN and KCl to bluegrass resulted in nominal damage and browning of the established grass in the Objective 3 experiment. Although burning did occur, it was not enough to (likely) preclude the response of corn to perceived competition, which reduces corn grain yield. The burning would have negatively affected the appearance of a golf green or homeowner lawn, but for the needs of avoiding a light quality response from corn, burning was inadequate. In response to this finding, we initiated two new grass management studies as described above. Both of these studies are providing appropriate results for concomitant reduction in competitiveness of grass and reduction in perception of competition by corn. What opportunities for training and professional development has the project provided?Allen Chen is a PhD student in the Department of Horticulture, Iowa State University supported by this project. He is actively involved with Objectives 1, 2, and 3. Drs. Fei and Lenssen serve as his co-major professors and Drs. Moore and Laird are on his graduate committee. Additionally, three undergraduate student hourly workers provide substantial help during summer and fall months with our field projects for plot maintenance and data collection. How have the results been disseminated to communities of interest?Allen Chen made an oral presentation on his research at the Annual Horticulture Research Retreat and another at the departmental seminar series. Our research was highlighted in the Research News published by the office of the vice-president for research at Iowa State University. Preliminary results were presented to the ISU Perennial Cover Crop working group at a monthly seminar in December 2017. The working group is composed of ISU research faculty. Monthly seminar speakers have been internal to ISU or from other institutions. The Dean of the College of Agriculture and Life Sciences ISU has supported this working group with funds to foster outreach to interested researchers and future competitive grant proposals to appropriate RFA. What do you plan to do during the next reporting period to accomplish the goals?For Objectives 1 and 2, the experiments initiated in 2017 will be continued with data collection occurring during the growing season. A growth chamber study to determine the environmental cues that trigger or break summer dormancy in sandbergbluegrass will be conducted in the fall and winter. For Objective 3, flaming treatments will be applied to the previously established Kentucky bluegrass in 2019, repeating the study initiated in 2018. Weed community will be assessed in all herbicide and flaming study plots in late June or early July 2018 and 2019. An additional acre of perennial grass strips, including kentucky bluegrass, will be established following soybean harvest in 2018 for a perennial grass flaming treatment study that includes corn in a strip tillage system. This study will include subplots with two nitrogen application rates banded within the strip-tilled corn zone.
Impacts
What was accomplished under these goals?
Objective 1. A total of 20 cultivars from seven cool-season grass species (sandburg bluegrass, red fescue, sheep fescue, tall fescue, sandberg bluegrass, western wheatgrass and an intermediate wheatgrass) were established at the Sorensen Research Farm near Ames, IA in the fall of 2017 by hand seeding. The size of each plot is 10 by 22.5ft (3.05 x 6.86 m) and all plots were irrigated as necessary. Three 15-inch grass-free strips were created by strip tilling into established grass stand in the spring of 2018. Seed of the corn hybrid DK57-75 was subsequently planted at a rate of 33,600-34,000 seed/acre on 30-inch centers. Measurements were done for grass plant height and leaf canopy height as well as the maize seedling count/plot and staging. Maize seedling count per plot varied greatly, ranging from 105 plants/plot (sheep fescue, cv. Quattro), which is 76.3% of the no-grass control to 135 plants/plot (kentucky bluegrass cv, A05-319), which is 98% of the no-grass control. However, maize development does not appear to be affected greatly by PGC as all plots exhibited uniform stages. Correlation analyses showed a weak, but negative correlation between maize seedling count per plot and grass plant height (R2=0.09) and canopy height (R2=0.20 or R2=0.09 with the two wheatgrass cultivars removed from analysis). Poor maize seedling emergence observed in some plots is likely caused by poor seed bed preparation which could be the result of the unique root profile of a particular PGC. This issue can be resolved with improved, dedicated tilling machinery. Objective 2. Twenty wild or unimproved accessions each for kentucky bluegrass, red fescue, and sandberg bluegrass were interplanted with maize in spring, 2017. Grass plugs established in a greenhouse from seed were transplanted into the field. Twenty individuals of each accession were space planted in alternate rows between maize (DeKalb DK57-75) which was planted at a rate of 33,600-34,000 seed/acre on 30-inch centers. Lateral spread of the grass was measured biweekly beginning at corn stage V6. Maize grain yield data measured from each plot was extrapolated to a per acre basis. In general, lateral spread, as measured by the percentage of ground cover varied greatly among species and among accessions within each species. Percentage of ground cover for kentucky bluegrass accessions ranged from 0.22% to 56.91%. Most kentucky bluegrass accessions continued to grow until the first week of July in 2017, after which green tissue declined continuously over the course of the data collection period. Sandberg bluegrass spread ranged from 0.08% to 32.72% overall depending on the accession and ranged from 0.08% to 10.98% if the likely misidentified accessions are removed. This low lateral spread reflects the bunchgrass nature of sandburg bluegrass. Most sandberg bluegrass plots experienced a sharp decline in green tissue presence during June and July of 2017 due to summer dormancy, a trait that is innately present in sandberg bluegrass and considered to be desirable in perennial ground covers. Percentage of ground cover for red fescue accessions remained relatively stable throughout the entire maize growing season. However, percentage of ground cover among red fescue accessions varied greatly from 1.81% to 64.63%. On average, there was no difference in maize grain yield between treatments. In fact, maize with red fescue as the PGC, which had consistent good ground cover throughout the summer, has the highest grain yield whereas maize grown with sandburg bluegrass as PGC, which had the lowest ground coverage throughout the summer, has the lowest grain yield. Objective 3. Managing kentucky bluegrass with urea ammonium nitrate (UAN) and potassium chloride (KCl) additions was examined in a field study in April 2017. Each fertilizer was applied to established grass at four rates. Somewhat contrary to reports in the turfgrass literature, neither urea nor KCl application caused substantial browning of leaves. Leaf burn did occur, particularly on tips and margins following application of the higher rates of urea, 200 and 250 lbs N/acre. However, following UAN application and a rainfall event, grass greenness ratings and red-far red ratios showed that grass competitiveness with corn likely was increased. Consequently, a new field study was developed and initiated in the field in May 2017. Three herbicides were selected for comparison of reducing competitiveness of kentucky bluegrass. Selection was based on two criteria: 1) herbicide is currently labeled for use on corn, and 2) herbicide is documented to require more than one application for causing mortality of turfgrass bluegrass. Formulated glufosinate, sethoxydim, and a combination of rimsulfuron and thifensulfuron methyl were applied at four rates to established kentucky bluegrass in the first week of May 2018 and the third week of May in 2017 and 2018. Results were similar among the three application dates. Glufosinate application resulted in substantial yellowing of grass at all application rates, with the greatest yellowing occurring with the highest two rates. Application of sethoxydim and rimsulfuron-thifensulfuron methyl did not result in a change in grass color, but the combination of rimsulfuron-thifensulfuron methyl resulted in a cessation of grass growth and development. However, red-far red ratios for all herbicide treatments were similar to those of the untreated controls. None of the herbicides applied at any rate in 2017 resulted in mortality or loss of grass stand, thus are suitable in corn-bluegrass weed management systems. A new study was initiated in 2018 comparing timing and intensity of flaming kentucky bluegrass. Treatments included flaming aboveground leaves each of the four weeks in May, and flaming for two, three, and four consecutive weeks. A single flaming of bluegrass resulted in elevated red-far red ratio, which is desirable to preclude the shade avoidance response from corn. Flaming two and three consecutive weeks provided elevated red-far red ratio for at least 4 weeks, after which bluegrass initiated green regrowth. At the time of writing this annual report, flaming in four consecutive weeks appears to have weakened the bluegrass substantially. Regrowth has initiated in the four times-burned plots but it is patchy. We will continue to monitor red-far red ratio and greenness index from the herbicide and flaming experiments until all plots have substantial regrowth providing data similar to the untreated controls.
Publications
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