Progress 10/01/12 to 09/30/17
Outputs
Target Audience:Scientists, outreach personell, and teachers involved with nutrition and soils for ornamental crops grown in soilless root substrates. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Opportunities were afforded me to attend conferences nationally and internationally where I accessed scientists working in my area of responsibility from whom I received background information and ideas for my profession. This advantage was reciprocal whereby those with whom I conferredreceived similar benefits from my expertise. Students working in this project gained insights and expertise which they have brought to their post-graduation positions. Benefits show up in their research and are transferred to students they in turn teach. How have the results been disseminated to communities of interest?Results were1) published in peer reviewed scientific journals, 2) orally presented at scientific meetings including the annual meetings of the Amer. Soc. for Hort. Sci and the ISHS International Symposiums on Growing Media and Soilless Cultivation in Sweden, France and Portugal, and 3)published in trade magazines for access by growers of ornamental crops and outreach personnel serving them. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
1. The effect of CO2 concentration (330 and 675 µL·L-1) and photosynthetic photon flux (PPF) (mean daily peaks of 550 to 1400 µmol·m-2·sec-1) on total mineral contents in shoots was studied in chrysanthemum [Dendranthema ×grandiflorum (Ramat) Kitam 'Fiesta'] during three times of the year. Growth (as measured by shoot dry weight) and shoot mineral contents of hydroponically grown plants were analyzed after five weeks. There was a positive synergistic interaction of CO2 concentration by PPF on growth with the greatest growth at high PPF (1400 µmol·m-2·sec-1) with high CO2 (675 µL·L-1). When growth was not used as a covariate in the statistical model, both CO2 concentration and PPF significantly affected content of all eight nutrients. However, after growth was included as a covariate in the model, nutrients were classified into three categories based on whether CO2 concentration and PPF level was needed in addition to growth to predict leaf nutrient content. Neither CO2 concentration nor PPF level were needed for Mg, Fe, and Mn contents, while PPF level was needed for N, P, K, and Ca contents, and both CO2 concentration and PPF level were required for B content. 2. There is little information addressing the impact of quantity of pre-plant phosphate charge in soilless substrate and leaching during production on soluble phosphate longevity when post-plant phosphate is omitted. Two experiments were conducted growing Petunia ×hybrida 'Primetime White' seedling crops over a 42-d period in a sphagnum peat moss-perlite substrate. Phosphate-phosphorus (P) charge levels of 0.03, 0.06, 0.12, and 0.18 kg.m-3 (0.05, 0.10, 0.20 and 0.30 lbs·yd-3, respectively) and 0, 20, and 50% leaching were tested. The first experiment was conducted in winter (late November through December) and the second in spring (mid-March through April). The minimum-targeted, soluble-bulk-solution phosphate-P level of 3 mg.L-1 (ppm) was achieved for 41 d in the winter with a phosphate-P charge of 0.06 kg.m-3 (0.10 lbs·yd-3) and 20% leaching . Longevity for this treatment was 4 d less in the spring. At 0% leaching, the soluble-bulk-solution phosphate-P level was above the minimum target level of 3 mg.L-1 (ppm) for the entire 42-d period in both seasons. Increasing the leaching from 20 to 50% resulted in a loss of longevity by 4 d in the winter and 6 d in the spring.
Publications
- Type:
Journal Articles
Status:
Awaiting Publication
Year Published:
2017
Citation:
Niedziela Jr., C.E., M.A. Depa, P.V. Nelson, D.H. Willits, M.M. Peet, D. A. Dickey, and N.C. Mingis. 2017. Effects of carbon dioxide and photosynthetic photon flux on mineral content in chrysanthemum allowing for growth as a covariate. HortScience.
- Type:
Journal Articles
Status:
Awaiting Publication
Year Published:
2017
Citation:
Horner, A.J.C., C.E. Niedziela Jr., P.V. Nelson, and D.A. Dickey. Effect of pre-plant phosphate charge and leaching on phosphorus longevity in soilless substrate. Journal of Environmental Horticulture.
- Type:
Journal Articles
Status:
Awaiting Publication
Year Published:
2017
Citation:
Barnes, J., P.V. Nelson, D. Hesterberg, W. Shi, and B.E. Whipker. 2017. Modeling impact of nitrogen carrier and concentration on root substrate pH. Journal of Plant Nutrition
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Progress 10/01/15 to 09/30/16
Outputs
Target Audience:Research scientists at governmental, university, and industrial organizations. Growers of crops in soilless root substrate. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Commercially important differences in substrate pH occurred across 13 plant species. This suggests the need to categorize greenhouse crops according to their association with substrate pH when developing fertilization programs. It further indicates a need in commercial production to analyze the substrate separately for these categories of crops for better management of pH. Expression of the current predicted PABRs assigned to fertilizers depends on the proportion of applied fertilizer taken up by the crop. Basic and neutral reaction fertilizers can have an acidic effect on substrate when applied to crops in high quantity. This calls attention to the importance of monitoring substrate electrical conductivity as a tool for regulating fertilizer application in accordance with crop demand. Furthermore, this justifies the value of understanding fertilizer use efficiency for implementation of best management practices. How have the results been disseminated to communities of interest?The resulting data was published in peer review journals. What do you plan to do during the next reporting period to accomplish the goals?In the final year of this project we plan to model the impact of mitrogen carrier and concentartion on soilless root substrate pH.
Impacts
What was accomplished under these goals?
In the first of three experiments the effects of 13 herbaceous plant species on pH in a 3 sphagnum peat moss: 1 perlite substrate was tested. A neutral fertilizer with a potential acidity/basicity rating (PABR) of 0 was applied. After 78 days, a decrease of 0.14 to 2.45 units occurred depending on species. In the second experiment four species covering the range of pH suppression were retested and resulted in similar decreases of 0.47 to 2.72 pH units. In the third experiment three fertilizers with PABRs of 193 acidity, 0 neutral, and 150 alkalinity were applied in a factorial design at 100 and 200 mg per liter nitrogen at each irrigation to kalanchoe, the species with the greatest pH suppression, for 56 days. When applied at the lower fertilizer rate the PABRs resulted in the final substrate pH levels of 4.68, 5.60, and 6.11 for the acid, neutral, and basic fertilizers while at the higher fertilizer rate pH levels of 3.97, 4.03, and 4.92 occurred for the acid, neutral and basic fertilizers. Expression of PABR depended on the balance between the abiotic (chemical) effect of fertilizers, which is typically acidic, and the biotic (physiological) effects of the fertilizers on microbes and plants. The PABR was best expressed when the fertilizer supply was just adequate or lower indicating a closer connection to the biotic effect.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Rippy, J.F.M., P.V. Nelson, D.L. Hesterberg, C.E. Niedziela Jr., E.J. Kamprath, and T. Bilderback. 2016. Importance of limestone specific surface for assessing neutralization effectiveness in soilless root substrate. Communications in Soil Science and Plant Analysis 47(4):521-526.
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Jeong, K.Y., P.V. Nelson, C.E. Niedziela Jr., W.F. Brinton, and W.C. Fonteno. 2016. Physical properties of peat-based substrates amended with a mature dairy cow manure compost before and after plant cultivation. J. Environ. Hort. 34(1):56-62.
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Jeong, K.Y., P.V. Nelson, C.E. Niedziela Jr., and D.A. Dickey. 2016. Effect of plant species, fertilizer acidity/basicity, and fertilizer concentration on pH of soilless root substrate. HortScience 51(12):1596-1601.
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Oh, Y-M., D.L. Hesterberg, P.V. Nelson, and C.E. Niedziela Jr. 2016. Desorption characteristics of three oxide minerals and a non-crystalline aluminosilicate for supplying phosphate in soilless root media. Communications in Soil Science and Plant Analysis 47(6):753-760.
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Oh, Y-M., P.V. Nelson, D.L. Hesterberg, and C.E. Niedziela Jr. 2016. Efficacy of a phosphate-charged soil material in supplying phosphate for plant growth in soilless root media. International Journal of Agronomy vol. 2016, Article ID 8296560, 10 pages, http://www.hindawi.com/journals/ija/2016/8296560/.
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Progress 10/01/14 to 09/30/15
Outputs
Target Audience:Scientific research personnell at governmental and industrial institutiions. Growers of plant crops in soilless root substrates. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Most growth during the annual cycle of the tulip crop occurs from autumn, shortly after planting, to late spring. Fertilization is conducted in fall and winter. Whether all macronutrients are required and the timing of these applications is not fully understood. Practical implications from this study include: 1) the importance of maintaining soil Ca levels throughout the fall to late spring period through use of limestone, 2) application of N, P, and Mg in split applications with smaller rates at planting and larger rates at emergence, and 3) application of all K at emergence in mid winter. How have the results been disseminated to communities of interest?Results were published in a journal paper and were presented orally at the Amer. Soc. Hort. Sci. meetings in New Orleans,La. What do you plan to do during the next reporting period to accomplish the goals?The first goal is to quantify the range of influence thirteen ornamental crop species can have on root substrate pH when grown in soilless root substrate. The second goal is to determine the interactive effects on substrate pH of fertilizer concentration versus the potential acidity/basicity rating of fertilizers.
Impacts
What was accomplished under these goals?
Tulips were grown under field conditions from mid-November through early-June. Plants were harvested and dissected into eight organs on twenty-one dates. These parts were dried, weighed, and analyzed for N, P, K, Ca, and Mg. A transition (as determined by curve join points) from a linear to a steep negative cubic response occurred prior to shoot emergence for N (82 days after planting (DAP)), at shoot emergence for K (93 DAP) and Ca (94 DAP), and after shoot emergence for Mg (102 DAP) and dry matter (118 DAP). A transition from a linear to a steeper linear response occurred at shoot emergence for P (93 DAP). Growth, organ development, and nutrient accumulation occurred continuously from planting to maturity (188 DAP), except for K which did not accumulate during the initial linear phase. Since the increase in accumulation of all five nutrients preceded the dry matter accumulation, these nutrients could be used as predictors in growth models.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2015
Citation:
Niedziela Jr., C.E., P.V. Nelson, and D.A. Dickey. 2015. Growth, development, and mineral nutrient accumulation and distribution from planting through post-anthesis shoot senescence in tulip. International Journal of Agronomy vol. 2015, Article ID 341287, 11 pages, http://www.hindawi.com/journals/ija/2015/341287/.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Barnes, B., P. Nelson, B.E. Whipker, D.A. Dickey, D. Hesterberg and W. Shi. 2015. Influence of nutrient accumulation in Chrysanthemum �morifolium on root substrate pH over time. Amer. Soc. Hort. Sci. Annual Meeting, New Orleans, LA. 4-7 Aug. HortScience 50(9):S141.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Barnes, B., P. Nelson, B.E. Whipker, D.A. Dickey, D. Hesterberg and W. Shi. 2015. Modeling the effects of macronutrients on fallow soilless root substrate pH. Amer. Soc. Hort. Sci. Annual Meeting, New Orleans, LA. 4-7 Aug. HortScience 50(9):S141.
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Progress 10/01/13 to 09/30/14
Outputs
Target Audience:Researchers at other academic and industrial organizations. Growers who produce plants in soilless root substrates. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Nearly all substrates in the container plant production industry are soilless. The primary problem associated with nutritional control in this production system is regulation of substrate pH. It is generally stated that over fifty percent of nutritional problems stem from improper substrate pH. While there are several factors that govern substrate pH, the one least understood is the impact of the specific ions, their form, and their ratios that make up the nutritional program. This study quantified the relative pH effects of these aspects of the five main macronutrient ions used to formulate fertilizers. Using this information, fertilizer manufacturers and growers can design their fertilizers to bring about more precise control of substrate pH. How have the results been disseminated to communities of interest?Results were disseminated through publication in journals and oral presentation at The International Symposium on Growing Media and Soilless Cultivation held in Leiden, The Netherlands. What do you plan to do during the next reporting period to accomplish the goals?The test crop will be tulip and objectives will include weekly measurement of growth of individual organs of the plant along with uptake of five macronutrients from fall planting to late spring senescence. The intended value of the data will be better planning of application timing for each nutrient ellement during production.
Impacts
What was accomplished under these goals?
Although many factors that influence substrate pH have been quantified, the effect from fertilizers continues to be elusive. A multifactorial experiment was conducted to test macronutrient effects using a rarely used statistical method known as the central composite design. Five nutrient factors, including nitrogen (N) carrier ratio (NH4+ vs. NO3-) and concentrations of phosphorus (P) (as H2PO4-), potassium (K), combined calcium (Ca) and magnesium (Mg), and sulfur (S), were varied at five levels each encompassing the proportionate range of these nutrients in commercial greenhouse fertilizers. Although a typical factorial experiment would have resulted in 55 = 3125 treatments, the central composite design reduced the number to 30 fertilizer treatments. An experiment was conducted twice in which 'Evolution White' mealy-cup sage (Salvia farinacea Benth.) was grown in 14-cm-diameter pots (1.29 L) in a 3 peat:1 perlite (v/v) substrate amended with non-residual powdered calcium carbonate to raise the substrate pH to 5.6 to 5.8. Harvests occurred after 3 and 6 weeks of growth. A statistical model described substrate pH over time with significant effects including four main effects of N carrier ratio, P, K, and combined Ca and Mg; three squared terms of N carrier ratio, P, and K; and seven interaction effects. The resulting model was used to calculate substrate pH levels between 25 and 45 days after planting, and it showed that N carrier had the greatest impact on substrate pH.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Barnes, J., P. Nelson, B.E. Whipker, D.A. Dickey, D. Hesterberg, and W. Shi. 2014. Statistical model for predicting macronutrient impacts on container substrate pH over time. HortScience, 49(2):207214.
Barnes, J., P. Nelson, W. Shi, D. Hesterberg, and B. Whipker. 2014. Fertilizer formulation effect on pH of fallow versus planted container substrate. The International Symposium on Growing Media and Soilless Cultivation. Acta Horticulturae 1034:465-469.
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Progress 10/01/12 to 09/30/13
Outputs
Target Audience:Research and extension personnell involved in the study of root substrates for container production of crops. Also crop management personell in crop production firms. Changes/Problems:
Nothing Reported
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 were disseminated through journal publication and presentations at professional meetings. What do you plan to do during the next reporting period to accomplish the goals?We will continue on with the original objective of identifing and quantifying those factors controlling substrate pH change during crop production in containerized soilless root substrates.
Impacts
What was accomplished under these goals?
Addition of mature dairy manure compost (DMC) to peat-moss based root substrate adversely increases bulk density (Db) while enhancing water sorption of the substrate. Substrate manufacturers typically raise the weight-based water content of soilless root substrate to 50% to ensure adequate wettability during crop establishment. This study investigated the possibility of lowering the percentage of water in substrate containing DMC in order to reduce Db without adversely affecting wettability. DMC was incorporated into a 3 sphagnum peat moss : 1 perlite (v:v) formula as a partial substitution for peat moss at 0, 7.5, 15, 22.5, and 30% by volume of the substrate. The water content of each of the five formulations was adjusted to approximately 10, 20, 30, 40, and 50% by weight. Wettability curves were generated to assess the impact of DMC content and initial water content on substrate wettability. The wettability level in the 0% DMC substrate at the industry norm water content of 50% was achieved in 7.5, 15, 22.5, and 30% DMC substrates at water contents of 40, 30, 20, and 20%, respectively. Based on previous research, 15% DMC is a desirable level for plant growth. The Db of 0 and 15% DMC mixes at 50% water content are 130 and 232 g/L (a Db gain of 78%), respectively. However, our research indicated that only 30% water is required in the 15% DMC mix for it to equal the wettability in the 0% DMC-50% water mix. This reduction lowered the Db of the 15% DMC-30% water mix to 180 g/L (a 39% Db gain), which cuts the Db gain due to the DMC addition in half and lowers the handling and transportation costs of this mix rendering it an economically viable option.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Barnes, J., P. Nelson, K.Y. Jeong, W.C. Fonteno, B. Whipker, and J. Frantz. 2013. Impact of mature dairy manure compost and water content on wettability and bulk density in peat moss-perlite root substrate. ISHS Intl. Symposium on Responsible Peatland Management and Growing Media Production. Acta Hort 982:75-80.
- Type:
Books
Status:
Published
Year Published:
2013
Citation:
Barnes, J. B. 2013. Quantifying the Factors that Influence Substrate pH. PhD Dissertation. Department of Horticultural Science, North Carolina State University. Raleigh.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2013
Citation:
Barnes, J., P. Nelson, W. Shi, D. Hesterberg, and B. Whipker. 2013. Fertilizer formulation effect on pH of fallow versus planted container substrate. Abstract. The International Symposium on Growing Media and Soilless Cultivation. Leiden, The Netherlands, 17-21 June 2013.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2013
Citation:
Barnes, J., P. Nelson, D. Hesterberg, W. Shi, and B. Whipker. 2013. Impact of Fertilizer Leach Fraction on Container Substrate pH. Abstract. The International Symposium on Growing Media and Soilless Cultivation. Leiden, The Netherlands, 17-21 June 2013.
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Progress 10/01/11 to 09/30/12
Outputs
OUTPUTS: Most greenhouse fertilizer solutions are acidic. The objective of this experiment was to determine whether proton contribution to substrate is exclusively due to the substrate retained fraction of fertilizer solution or is additionally due to the leachate fraction of fertilizer passing through the substrate. To test this question, fallow 14cm diameter pots containing 3 sphagnum peat moss:1 perlite substrate were hydrated to container capacity with deionized water and placed on a greenhouse bench to dry. Each time substrates dropped to approximately 50% moisture content, substrate was treated with an industry fertilizer (17-2.2-14.1, 7.1 mmol N, pH 4.1) at leach fractions of 0% (closed system sub-irrigation) and 20% (open system top irrigation). There were a total of five harvests, one control harvested prior to first fertilizer application plus four harvests after fertilizer applications. Over time, substrate pH decreased from 6.0 to 5.4. Overall, substrate pH curves for the two treatments showed similar proton contributions from both treatments. These results indicate there was little or no contribution of protons by the leachate fraction of applied fertilizer above that contributed by the proportion of fertilizer solution retained by the substrate. From previous work testing the impact of 30 fertilizers on substrate pH, five fertilizer formulations that elicited the widest range of substrate pH biotic impacts during Salvia farinacea cv Evolution White cultivation were chosen for a follow up study to determine the abiotic impact of these fertilizers on fallow substrate. A 3 sphagnum peat moss:1 perlite substrate was formulated and adjusted to pH 5.6. Three sets of pots (14 cm diameter) were filled with substrate. Salvia plugs were installed in the first set for cultivation while the second set was left fallow followed by fertigation of both sets with 400 mL of fertilizer solution (each at 7 mmol N concentration and unaltered pH 4.2) to bring them to approximately container capacity. The third set of pots (control) were left fallow and irrigated with 400 mL deionized water instead of fertilizer solution. Each time cultivated substrates dried to approximately 50% of container capacity, 200 mL of fertilizer solution was applied to sets one and two and 200 mL deionized water to set three for a total of 11 applications. Substrates were harvested after 3 and 6 weeks. The pH of control substrate was 5.69 for both harvests. For the first and second harvest, cultivated substrate pH ranged from 6.08 to 5.03 and 6.22 to 4.85, respectively, while pH values of fallow substrate that received fertilizer solutions ranged from 5.66 to 5.19 and 5.44 to 4.97, respectively. Contrary to the expected abiotic effect of these acidic fertilizer solutions, pH in the fertilized fallow pots increased or decreased in a similar but diminished fashion to the changes that occurred to the pH in the cutivated pots. These results suggested a biotic effect in the fallow substrates due possibly to microflora and indicate the need to take into account a biotic effect of microbes when assessing the abiotic effect of fertilizer solutions on substrate pH. PARTICIPANTS: This study constituted the Ph.D. thesis project for Jared Barnes. It was instrumental in his training for a research career. TARGET AUDIENCES: The target audience includes research and extension personnell involved in the study of root substrates for container production of crops. It also includes crop management personell in crop production firms. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The greatest challenge to commercial production firms, as well as researches, in their irrigation and nutritional programs is that of control of the root substrate pH over time. The solution to this problem rests in the need for quantification of the proton shifts in substrate as a consequence of fertilizer formulation, concentration, volume of application, and frequency of application. Insufficient information existed for this quantification prior to this study. Our results aid in this quantification by demonstrating that fertilizer leaching through the substrate profile during fertilization need not be taken into account in these calculations. However, earlier assumptions that the biotic control of proton shifts in the root substrate result exclusively from plant interactions with fertilizer are not accurate. Microbial activity in the substrate also influences proton shifts and must be taken into account.
Publications
- Ahmad, I., J. M. Dole, and P. Nelson. 2012. Nitrogen application rate, leaf position and age affect leaf nutrient status of five specialty cut flowers. Scientia Hort., 142:14-22.
- Barnes, J., P. Nelson, D. Hesterberg, K. Y. Jeong, and B. E. Whipker. 2012. Evaluation of a rapid, automated titration system for evaluating lime requirements for peat-based substrates. Annual Meeting of the Amer. Soc. Hort. Sci., Miami, FL. July 31 to Aug 3. ASHS Annual Conf. Program. p.101.
- Nelson, P. V., C. Y. Song, J. S. Huang, C. E. Niedziela, Jr., and W. H. Swallow. 2012. Relative effects of fertilizer nitrogen form and phosphate level on control of bedding plant seedling growth. HortScience. 47(2):249-253.
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Progress 10/01/10 to 09/30/11
Outputs
OUTPUTS: 1. Addition of mature dairy manure compost (DMC) to peat-moss based root substrate adversely increases bulk density (Db) while enhancing water sorption of the substrate. Substrate manufacturers typically raise the weight-based water content of soilless root substrate to 50% to ensure adequate wettability during crop establishment. This study investigated the possibility of lowering the percentage of water in substrate containing DMC in order to reduce Db without adversely affecting wettability. DMC was incorporated into a 3 sphagnum peat moss : 1 perlite (v:v) formula as a partial substitution for peat moss at 0, 7.5, 15, 22.5, and 30% by volume of the substrate. The water content of each of the five formulations was adjusted to approximately 10, 20, 30, 40, and 50% by weight. Wettability curves were generated to assess the impact of DMC content and initial water content on substrate wettability. The wettability level in the 0% DMC substrate at the industry norm water content of 50% was achieved in 7.5, 15, 22.5, and 30% DMC substrates at water contents of 40, 30, 20, and 20%, respectively. 2. Fertilizers with a high proportion of nitrogen (N) in the nitrate form are used in the ornamental industry to promote compactness in plants. While the common belief is that it is the high proportion of nitrate that causes compactness, these formulations also contain no or a low level of phosphate which can also cause compactness. This study was conducted to assess the relative effects of nitrate to ammonium ratio and phosphate supply, as found in high nitrate fertilizers, on seedling shoot growth. A series of fertilizers was formulated in which the level of phosphate and proportion of N in the nitrate form were varied factorially. Additionally, commercial fertilizers varying in these same two nutrient components were tested to verify the results obtained using the formulated fertilizers. Test plants included gomphrena (Gomphrena globosa L.), impatiens (Impatiens wallerana Hook. F.), petunia (Petunia x hybrida Juss.), marigold (Tagetes erecta L.), and tomato (Solanum esculentum Mill.) grown as plug seedling crops. A strong inverse relationship occurred between supply of phosphate and extent of compactness. The relationship between proportion of N in the nitrate form and compactness was comparatively small. In most comparisons within the study, shoot size increased with increasing proportion of nitrate, contrary to the common belief. These data indicate that it is the limited phosphate level in high nitrate fertilizers that accounts for compactness rather than the high proportion of N in the nitrate form. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: The root substrate formulating industry will benefit directly from this information. Growers who formulate their own substrate will benefit equally. Growers who use the substrate will benefit through easier handling of the substrate. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
1. Based on previous research, 15% DMC is a desirable level for plant growth. The bulk density (Db) of 0 and 15% mature dairy manure compost (DMC) mixes at 50% water content are 130 and 232 g/L (a Db gain of 78%), respectively. However, our research indicated that only 30% water is required in the 15% DMC mix for it to equal the wettability in the 0% DMC-50% water mix. This reduction lowered the Db of the 15% DMC-30% H2O mix to 180 g/L (a 39% Db gain), which cuts the Db gain due to the DMC addition in half and lowers the handling and transportation costs of this mix. This is an economic advantage for the root substrate formulation industry because it lowers the price of their products to greenhouse growers. It is an advantage for growers because working with lighter substrate eases the labor input in plant establishment. 2. Results of the high nitrate/low phosphate fertilizer research dispel the false assumption that it is the nitrate proportion that yields compact growth. By establishing the fact that it is primarily the low phosphate level that is accountable it allows growers to more judiciously select fertilizers for compactness. It is particularly helpful to growers who formulate their own fertilizers. This research has been responsible in great part to the national and international movement of the ornamental and young plant industries toward use of modest phosphate deficiencies for production of the compact plants required in their markets.
Publications
- Jeong, K. Y., Nelson, P. V., Frantz, J., and Brinton, W. 2011. Impact of composted dairy manure on pH management and physical properties of soilless substrate. Acta Hort. 891:173-180.
- Fisher, P. R., Huang, J, Argo, W. R., and Nelson, P. V. 2011. The LimeR series of analytical protocols for lime in container substrates. Acta Hort. 891:111-118.
- Whipker, B. E., Cavins,T. J., Gibson, J. L., Dole, J. M., Nelson, P. V., and Fonteno, W. 2011. Plant Nutrition. In: C. Beytes (ed.). Ball Red Book, 18th. Edition. Ball Publishing, Batavia, IL.
- Whipker, B. E., Cavins,T. J., Gibson, J. L., Dole, J. M., Nelson, P. V., and Fonteno, W. 2011. Water, media, and nutrition testing. Pg 49-66. In: C. Beytes (ed). Ball Red Book, 18th. Edition. Ball Publishing, St. Charles, IL.
- Nelson, P. V. 2012. Greenhouse operation and management. 7th edition. Prentice-Hall, Upper Saddle River, NJ 607 pp.
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Progress 10/01/09 to 09/30/10
Outputs
OUTPUTS: Liming materials are required to neutralize acidity in peat moss to make it a suitable substrate for growing container crops. A series of time-consuming incubations of peat:lime mixtures are typically used to determine the liming rate to achieve a desired pH. Our objective was to evaluate the utility of a rapid, acid-base titration method for predicting calcite (CaCO3) requirement. In this method, peat moss with an initial pH of 3.7 was titrated in aqueous suspension with 0.1 M NaOH or 0.1 M HCl solution from pH 3 to 11 (forward titration), then from pH 11 to 3 (backward titration). Because of hysteresis, the forward and backward titration curves were averaged to predict calcite requirements. For comparison, peat moss samples were incubated in plastic bags for 13 days after applying calcite at rates between 0 and 1.5 mol CaCO3/kg peat moss (dry weight basis), and pH was monitored until a steady-state was established. The pH achieved by calcite incubation could be predicted up to pH 6.2 by the averaged acid-base titration curve. Above pH 6.2, calcite solubility limits caused a deviation between the two methods as the pH in the incubation experiment reached a plateau with increasing calcite additions. Geochemical speciation calculations showed that calcite solubility limits imposed by atmospheric CO2 and dissolved Ca activity restricts the maximum pH achievable. Nevertheless, the acid-base titration is a quick method for accurately predicting calcite requirements of acidic peat moss for target pH levels ≤ 6.2. The Rhizon soil moisture sampler (RS) provides a non-destructive method for extracting soil solution. The RS with a 2.5 mm outer diameter draws solution from a small area and raises the question whether it can represent the whole pot. Also, when placed diagonally or vertically in a pot more solution would be expected to be collected from the base relative to the top of the pot due to lower water container capacity at the top. When 5 RS samplers were placed horizontally at 1, 3, 5, 7, and 9 cm above the bottom of 16.5 cm diameter, 10 cm substrate depth, 1.8 L volume pots containing lettuce plants, the following average gradients from bottom to top of pot were found: EC 1.1 - 1.8 dS/m, pH 6.3 - 5.6, and relative rate of solution extracted 1 : 0.32. When the solution from a Rhizon sampler oriented diagonally (D-RS) from top to bottom of the pot was compared to the five horizontally and equally spaced Rhizon samplers (H-RS), pH level in the D-RS extract was equivalent to that in the lower 20% of the substrate column (H-RS1). EC in the lower three H-RS and D-RS extracts were within standard error of each other. A comparison of extracts from D-RS, pour-through (PT), and saturated media extract (SME) showed equivalent EC levels for the D-RS (1.21) and PT (1.26) but lower values for SME (0.69). The pH levels were significantly different for all three methods and were 6.6, 6.2, and 5.5 for the PT, D-RS, and SME methods, respectively. Data indicated that the D-RS drew solution primarily from its lower end, far in excess of the proportion suggested by the five H-RSs. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Scientists working in the area of ornamental soils and plant nutrition. Personnell associated with greenhouse firms. Companies producing soilless root substrates. Oraganizations testing soilless root substrates. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Soilless root substrate formulation companies need an easier and more rapid method for titrating peat moss to determine the amount of limestone each batch will require when it is incorporated into their root substrate formulations. The procedure developed in this project meets this need. The procedure is of equal value to research scientists because the titrants used are a strong acid and strong base, free of solubility issues. The current limestone incubation method being replaced, while accurately indicating the amount of limestone required, does not quantify the true acidity of peat moss or amount of base required to shift pH up to a desired set point. Results indicated that the Rhizon soil moisture sampler is an effective device for extracting unaltered substrate solution for commercial and research purposes. It further indicated that most of the extracted solution comes from the lower end of the sampler. This points out the importance of placing the lower end of the RS at the level where the test analysis is desired or placing it in a horizontal position. The pour-through extraction method is the current method for obtaining unaltered substrate solution. The advantage of the Rhizon is less alteration of the substrate water and nutrient regimes during the extraction process because, unlike the pour-through system, no water is added in the process. This is very important for research where successive samples are drawn.
Publications
- Nelson, P. V., Pitchay, D. S., Niedziela, C. E. Jr., and Mingis, N. C. 2010. Efficacy of soybean-base liquid fertilizer for greenhouse crops. J. Plant Nutrition. 33:351-361.
- Nelson, P. V., Niedziela, C., and Pitchay, D. 2010. Effectiveness, ammonium impact and potassium adequacy of soybean-base liquid fertilizer on bedding plants. J. Plant Nutrition 33(5):724-735.
- Song, C.Y., Nelson, P. V., Niedziela, C. E. Jr., and Cassel, D. K. 2010. Efficacy and physical properties of ground, composted rice hills as a component of soilless substrate for selected bedding plants. J. of Applied Horticulture. 12(1):16-20.
- Taylor, M. D., Nelson, P. V., Frantz, J. M., and Rufty, T. W. 2010. Effect of phosphorus deficiency and high temperature on ammonium and nitrate uptake and acidification by Pelargonium. J. Plant Nutrition.33(5):701-712.
- Nelson, P. and Niedziela, C. 2010. Ammonium toxicity symptoms in bedding plants. GPN Greenhouse Product News 20(11):34, 36, 38, 40.
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Progress 10/01/08 to 09/30/09
Outputs
OUTPUTS: Dairy cow manure compost (DMC) was evaluated to quantify its impact on soilless substrate pH establishment and stabilization throughout crop time and to test its effect on physical properties of substrate. Peat moss plus DMC (at 5 to 30% by volume) was held constant at 75% volume and perlite at 25% without limestone. Two additional control treatments of 75% sphagnum peat moss and 25% perlite were formulated with and without agricultural dolomitic limestone. Pot chrysanthemum cv. Kory plants were transplanted into 16.5 cm diameter (1.4 L) plastic pots and fertilized at each irrigation with 17N-2.2P-14.1K neutral fertilizer. Additions of 0 to 30% DMC resulted in initial substrate pH levels of 3.1 to 6.5. Although pH declined during plant production, the decline was similar in the agricultural limestone and the 20 to 30% DMC treatments that had similar initial pH levels. Thus, pH buffering capacity of DMC was similar to the limestone. The initial EC levels for all substrates were within the acceptable range for seedlings and bedding plants. Magnitude of shrinkage did not relate to addition of DMC and was of little commercial significance. Irrespective of time in the cropping cycle, DMC resulted in increased dry bulk density (Db), decreased total porosity (TP) and container capacity (CC), and little effect on air space (AS). AS levels were in a good range of 15% and above for the 7.6 cm tall test cylinders. End of crop tissue analysis indicated that DMC resulted in higher leaf concentrations of potassium, sulfur, copper, iron, and manganese and lower, but adequate, calcium and magnesium concentrations. Maximum plant growth (dry weight) occurred with 15% DMC in Expt. 1 and with 10% DMC in Expt. 2. All limestone and a portion of peat moss were effectively replaced with DMC. 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
Mature dairy manure compost incorporated into sphagnum peat moss base soilless container substrate without any limestone addition is as effective in establishing initial target pH and holding it against change over time as limestone.
Publications
- Jeong, K.Y., Hesterberg, D., Nelson, P., and Frantz, J. 2009. Predicting calcite (CaCO3) requirements of sphagnum peat moss from pH titration curves. 106th Annual Meeting of the Amer. Soc. Hort. Sci. St. Louis, MO. HortScience 44(4):1020.
- Jeong, K.Y., Nelson, P., Frantz, J., and Brinton, W. 2009. Impact of composted dairy manure on pH management and physical properties of soilless substrate. Intl. Symposium on Growing Media and Composting. Charlotte, NC. June 1-5. Conf. Program. P.51., Intl. Soc. Hort. Sci.
- Taylor, M., Nelson, P., and Frantz, J. 2009. Sudden substrate pH decline. Greenhouse Product News - Big Grower Supplement 19(1):16-18.
- Taylor, M., Nelson, P., and Frantz, J. 2009. A declining pH problem with geraniums. OFA Bulletin No. 917. p. 15-19.
- Nelson, P., Niedziela, C., and Pitchay, D. 2009. Daniels Plant Food: Does it work Grower Talks. 72(10):32,34,36.
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Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: Sudden pH decline (SPD) describes the situation where crops growing at an appropriate pH rapidly (within 1-2 weeks) cause the substrate pH to shift downward one to two units. 'Designer Dark Red' geraniums Pelargonium hortorum Bailey) were grown in three experiments to assess possible effects of light on SPD and phosphorous (P) uptake. The first experiment tested the effect of four light intensities (105, 210, 575, and 1020 25 umol per square meter per second) on substrate acidification. At 63 days, substrate pH declined from 6.0 to 4.8 as light intensity increased. Tissue P of plants grown at the highest two light levels was extremely low (0.10%-0.14% of dry weight). P stress has been reported to cause acidification. Because plants in the two lowest light treatments had adequate P, it was not possible to determine if the drop in substrate pH was a direct light effect or a combination of light and P. The second experiment used a factorial combination of the three highest light levels from Expt. 1 and five preplant P rates (0, 0.065, 0.13, 0.26, or 0.52 g per liter substrate) to assess this question. When tissue P concentrations were deficient, pH decreased by 0.6 to 1.0 pHunits within 2 weeks and deficiency occurred more often with high light intensity. These data indicated that P deficiency caused substrate acidification and indicated the possibility that P uptake was suppressed by high light intensity. The third experiment was conducted in hydroponics to determine the direct effect of high light intensity on Puptake. In this experiment, cumulative P uptake per gram root and the rate of P uptake per gram root per day both decreased 20% when light intensity increased from 500 to 1100 umol per square meter per second. It is clear from this study that P deficiency causes geraniums to acidify the substrate and that high light suppresses P uptake. It is not clear if high light can cause SPD if tissue P is adequate. 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
While we had a suspicion at the start of the project that the environmental factors of light and temperature might control sudden pH decline (SPD)of root substrate by geranium, we did not realize that the mode of action would involve mineral nutrition. Superoptimal light intensity was found to suppress phosphorus uptake which in turn can cause SPD. Superoptimal temperature caused an increase in the uptake ratio of ammoniacal to nitrate nitrogen which results in substrate acidification.
Publications
- Taylor, M.D., Nelson, P.V., and Frantz, J.M. 2008. Substrate acidification by geranium: Temperature effects. J. Amer. Soc. Hort. Sci. 133(4):1-7.87.
- Taylor, M.D., Nelson, P.V., and Frantz, J.M. 2008. Substrate acidification by geranium: Light effects and phosphorus uptake. J. Amer. Soc. Hort. Sci. 133(4):1-6.
- Rippy, J.F.M., Nelson, P.V., Bilderback, T.E., Hesterberg, D.L., Kamprath, E.J., Swallow, W.H., and Jahn, D. 2008. Evaluation of limestone physical and chemical properties on neutralization capacity. Acta Hort. (ISHS) 779:139-148.
- Niedziela, C.E., Kim, S.H., Nelson, P.V., and DeHertogh, A.A. 2008. Effects of N-P-K deficiency and temperature regime on the growth and development of Lilium longiflorum `Nellie White' during bulb production under phytotron conditions. Scientia Horticulturae 116:430-436.
- Gibson, J.L., Pitchay, D.S., Williams-Rhodes, A.L., Whipker, B.E., Nelson, P.V., and Dole, J.M. 2007. Nutrient Deficiencies in Bedding Plants: A pictorial guide for identification with correction. Ball Publishing, Batavia, IL. 369pp.
- Taylor, M.D., Nelson, P.V., and Frantz, J.M. 2007. Effect of high temperature on substrate acidification by geranium. Southern Nursery Assoc. Research Conf. Proc. 52:101.1-101.7.
- Taylor, M.D., Nelson, P.V., and Frantz, J.M. 2007. Effect of high temperature on extreme substrate acidification by geranium Pelargonium x hortorum Bailey. 104th Annual Meeting of the Amer. Soc. Hort. Sci., Scottsdale, Ariz. HortScience 42(4):874.
- Taylor, M.D., Nelson, P.V., Frantz, J.M., and Rufty, T. 2007. Effect of phosphorus deficiency and high temperature on ammonium and nitrate uptake by geranium (Pelargonium x hortorum Bailey). HortScience 42(4):890.
- Taylor, M.D., Nelson, P.V., and Frantz, J.M. 2007. Are your geraniums suicidal GMPro 27(12):25-29.
- Gibson, J., Whipker, B., and Nelson, P. 2008. Diagnosing abiotic disorders in the greenhouse. Amer. Nurseryman 207(3):12,14,16.
- Gibson, J.L., Nelson, P.V., Pitchay, D.S., and Whipker, B.E. 2008.Identifying nutrient deficiencies of bedding plants. The Mayflower,2007-2008, no. 2: 1-4.
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Progress 10/01/06 to 09/30/07
Outputs
The cause of sudden substrate pH decline by geranium is unknown and may be due to a shift in cation-anion balance. Nitrogen plays a very important role in cation-anion balance since it can be absorbed as a cation or anion. Studies have shown that P deficiency can suppress nitrate uptake causing a shift in the cation-anion uptake ratio, potentially causing acidification of the rhizosphere. Geraniums (Pelargonium x hortorum Bailey 'Designer Dark Red') were grown in 200 L hydroponic tanks at 2 temperatures (18/22 and 22/26C night/day) and with or without P. Three, 11, and 19 days after transplanting (DAT), plants were placed into an identical solution containing either N-15 labeled ammonium or nitrate for 24 hours. Influx of ammonium and nitrate were not significantly affected by temperature, but P starvation suppressed ammonium uptake at 19 DAT and nitrate at 11 and 19 DAT. At the control temperature treatment the ammonium:nitrate influx ratio increased significantly from
0.34 to 0.46 and 0.30 to 0.38 when plants did not receive P at 11 and 19 DAT, respectively. Solution pH was maintained at 5.8 throughout the experiment and tanks with plants receiving P consumed less than half the mEq of titrating base per gram dry weight plant than tanks with plants that were devoid of P. Data indicate P stressed geraniums suppress uptake of N (primarily nitrate) and increase the rate of acidification, which offers one explanation for sudden substrate pH decline. High temperature was investigated as a second potential cause of acidification. With increasing increments of temperature, (14/10, 18/14, 22/18 and 26/22C day/night) substrate pH declined from 6.8 to 4.6 at 63 d. Tissue P was deficient (below 0.2) in the 3 highest temp treatments and it was unclear whether the cause of substrate acidification was due to P deficiency and/or high temperature. A subsequent experiment tested a factorial arrangement of 3 temperatures (18/14, 22/18 and 26/22C day/night) by 5
pre-plant P rates (0, 0.065, 0.13, 0.26, and 0.52 g P per L substrate). At 28 d tissue P was adequate in plants at all temperature and P treatments except 0. Yet, pH was lower in the high temperature treat with all P rates except the highest, indicating that temperature acts independent of tissue P level. At 63 d in the 0.065 and 0.13 P treatments, tissue P was deficient but not significantly different and pH decreased with increasing temperature from 5.6 to 4.8 and 5.9 to 4.7, respectively. In the 0.26 P treatment, tissue P was adequate at low temperature and deficient at the two higher temperatures yet pH decreased as temperature increased. In the highest P treatment all tissue P levels were adequate and pH declined with each increase in temperature. Again, the 63 day results showed that temperature acts independent of tissue P. When plants received P, pH fell to below 5.2 by 57 d when temperature was high. These data indicate high temperature stressed geraniums increase the rate of
acidification, which offers a second explanation for sudden substrate pH decline.
Impacts
Geraniums are the highest valued bedding plant of the $2.53 billion bedding plant industry (USDA, 2005). During the past 20 years growers have been plagued with a large, unpredictable, and sudden pH decline in the root substrate (SPD). Geraniums as well as at least ten other crops are devastated by SPD. Clearly, a signal is perceived in the plant that triggers SPD. However, the signal(s) have been unknown. Our study has unveiled three signals that can cause SPD. These include phosphorus deficiency stress, adversely high temperature, and adversely high light intensity. All can easily be detected and prevented. This now affords the floral production industry a means of averting the heavy economic losses they have been experiencing.
Publications
- Kim, S. H., Niedziela, C. E., Nelson, P. V., De Hertogh, A. A., Swallow, W. H., and Mingis, N. C. 2007. Growth and development of Lilium longiflorum `Nellie White' during bulb production under controlled environments: I. Effects of constant, variable and greenhouse day/night temperature regimes on scale and stem bulblets. Scientia Horticulturae 112:89-94.
- Kim, S. H., Niedziela, C. E., Nelson, P. V., De Hertogh, A. A., Swallow, W. H., and Mingis, N. C. 2007. Growth and development of Lilium longiflorum `Nellie White' during bulb production under controlled environments: II. Effects of shifting day/night temperature regimes on scale bulblets. Scientia Horticulturae 112:95-98.
- Gibson, J. L., Williams, A., Whipker, B. E., Nelson, P. V., Dole, J. M., Cleveland, B., and Walls, F. R. 2007. Foliar symptomology and tissue concentrations of nutrient-deficient vegetative strawflower plants. Comm. Soil Science Plant Analysis 38(17):2279-2294.
- Taylor, M. D. 2007. Elucidation and control of sudden pH decline of geranium. Ph.D. Thesis, N.C. State. Univ., Raleigh, NC.
- Niedziela, C. and Nelson, P. 2007. Topple troubles in tabletop tulips. Floraculture Intl. 16(8).
- Taylor, M. D. and Nelson, P. V. 2007. Five factors controlling substrate pH. Amer. Nurseryman 206(8):36-44.
- Taylor, M. D. and Nelson, P. V. 2007. Do you have suicidal geraniums? N.C. Flower Growers' Bulletin 52(4):1, 3-5.
- Godwin, P., Dole, J., and Nelson, P. 2007. Managing cut flower nutrition in the field. The Cut Flower Quarterly 19(2):20-25.
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Progress 10/01/05 to 09/30/06
Outputs
Sudden pH decline (SPD) of root substrate mediated by geranium is a serious commercial problem and the signal causing it is unknown. Since low Fe and P stresses cause many other plants to acidify the rhizosphere, these stresses were applied in a hydroponic greenhouse study to 2 geranium (Pelargonium x hortorum Bailey) cultivars prone to SPD and 2 resistant. Treatments consisted of a complete nutrient solution and two similar solutions devoid of either Fe or P. Solution pH was set at 5.8 and changed weekly. Since all cultivars showed similar responses, results were combined. Twenty days after transplanting, plants in all treatments, including control, caused solution pH to fall below 5. At 37 days, solution pH levels for control, minus Fe, and minus P treatments were 4.1, 3.7, and 3.6, respectively. Results indicated that geranium is an acidifying plant when N is supplied as 15% NH4 and 85% NO3. Additionally, low Fe and low P stresses increase the acidification rate.
Five additional experiments were conducted to explore the potential role of flowering, light intensity (105, 210, 450 and 1020 micro mol per sq. m per sec), and temperature (14/10, 18/14, 22/18 and 26/22C day/night) as signals causing SPD. In the initial experiment, plants allowed to form flowers had a final substrate pH of 5.7 compared to 6.3 for plants where flowers were removed. Increasing increments of temperature resulted in pH decline from 6.8 to 4.6 and increasing light intensity from 6.1 to 4.8. In later experiments, the flower removal and high light effects were not duplicated. Temperature effects, although not as large as in the first trial, were significant with the lowest value of 5.5 attained in the high temperature treatment. There is an indication that an additional factor is involved in expression of the light, temperature, and flowering control of acidification.
Impacts
Nearly all greenhouse crops, about 60 percent of landscape nursery crops, most seedlings for horticultural, forestry, and agronomic crops, and all house plants are grown in container substrates. These substrates are mixtures of materials that only infrequently include soil and are not well buffered against pH shifts. Most contain acidic components such as peat moss, pine bark, or coir coconut fiber that require limestone for upward pH adjustment. Current tests used for defining the neutralization capacity of limestone work for soil in the field but not for container substrates. As a result, initial substrate pH is not consistently achieved and there are major problems of pH drift away from the initial target level. The perennial statement made at grower conferences is, If substrate pH could be controlled, 50 to 75 percent of all nutritional problems would be avoided. Results from this study will pave the way for soilless substrate formulators to measure the
neutralization requirement of individual substrate mixes or their components as well as to determine the neutralization capacity of individual lots of limestone. The two pools of data will be used to match limestone with substrate more accurately than is currently possible with the resulting benefit of more precise achievement and control of target pH in container substrates.
Publications
- Taylor, M.D., P.V. Nelson, and J.M. Frantz. 2006. Impact of flower removal and light and temperature stresses on acidification of nutrient solution by geranium. 103rd Annual Meeting of the Amer. Soc. Hort. Sci., New Orleans, La. HortScience 41(4):970.
- Taylor, M.D., P.V. Nelson, and J.M. Frantz. 2006. Impact of low iron and phosphorus stresses on acidification of nutrient solution by geranium. 103rd Annual Meeting of the Amer. Soc. Hort. Sci., New Orleans, La. HortScience 41(4):970.
- Nelson, P., B. Whipker, J. Dole, D. Pitchay, J. Gibson, A. Rhodes, and B. Cleveland. 2006. Diagnosis of nutrient deficiencies in bedding plants. GPN (Greenhouse Product News) Vol 17(1).
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Progress 10/01/04 to 09/30/05
Outputs
Particle size distribution and CaCO3 content have been deemed adequate measures to classify agricultural limestones for field use but do not adequately define neutralization capacity to meet horticultural container substrate specifications. We evaluated the effects particle size, CaCO3 and MgCO3 content, internal porosity, hardness, soundness, specific gravity, and specific surface of limestones from twenty quarries (selected to maximize differences in properties) on limestone reactivity in order to determine the degree of influence of these factors on neutralization capacity of the limestones. Data for all these physical/chemical properties were analyzed in multiple regressions with particle size included and with particle size held constant at coarse [30-50 mesh (600-300 microns)], medium [170-200 mesh (90-75 microns)], and fine [325-400 mesh (45-38 microns)] fractions. Particle size accounted for slightly more than half of the neutralization capacity of the
limestones. With particle size held constant, CaCO3 or MgCO3 had the greatest impact on limestone reactivity, accounting for about 50% of the reactivity. Specific surface did not correlate significantly to particle size, thus addressed an additional aspect of limestone reactivity. Porosity, hardness and bulk density were highly correlated to each other, thus measured the same aspect of limestone reactivity. Soundness had little influence on reactivity. Adding specific surface measurements to particle size and CaCO3 content increased the power of the reactivity prediction model to 82% of the reactivity. The addition of a fourth measurement; either porosity, hardness or bulk density, increased the model strength to only 88%. Adding specific surface measurements to the description of limestones used for horticultural purposes would be advantageous.
Impacts
Nearly all greenhouse crops, about 60 percent of landscape nursery crops, most seedlings for horticultural, forestry, and agronomic crops, and all house plants are grown in container substrates. These substrates are mixtures of materials that only infrequently include soil and are not well buffered against pH shifts. Most contain acidic components such as peat moss, pine bark, or coir coconut fiber that require limestone for upward pH adjustment. Current tests used for defining the neutralization capacity of limestone work for soil in the field but not for container substrates. As a result, initial substrate pH is not consistently achieved and there are major problems of pH drift away from the initial target level. The perennial statement made at grower conferences is, If substrate pH could be controlled, 50 to 75 percent of all nutritional problems would be avoided. Results from this study will pave the way for soilless substrate formulators to measure the
neutralization requirement of individual substrate mixes or their components as well as to determine the neutralization capacity of individual lots of limestone. The two pools of data will be used to match limestone with substrate more accurately than is currently possible with the resulting benefit of more precise achievement and control of target pH in container substrates.
Publications
- Rippy, J.F.M. and Nelson, P.V. 2005. Soilless root substrate pH measurement technique for titration. HortScience 40(1):201-204.
- Rippy, J.F.M, Nelson, P.V., Hesterberg, D.L. and Kamprath, E.J. 2004. Specific surface versus particle diameter of limestones. 101st. Annual Meeting of the Amer. Soc. for Hort. Sci., Austin, Tex. HortScience 39(4):877.
- Rippy, J.F.M., Nelson, P.V. and Bilderback, T.E. 2005. Cation exchange capacity and base saturation of 64 peat mosses. 102nd. Annual Meeting of the Amer. Soc. for Hort. Sci., Las Vegas, Nev. HortScience 40(4):1124.
- Rippy, J.F.M. 2005. Factors affecting pH establishment and maintenance in peat moss-based substrates. Ph.D. Thesis, N.C. State Univ., Raleigh.
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Progress 10/01/03 to 09/30/04
Outputs
Agricultural limestone is classified primarily by its particle size distribution. This is adequate for agronomic crops but not for horticultural container substrate crop applications. We evaluated specific surface area (sq. m/g) (SSA) to determine its additive or substitutive value relative to particle size for assessing neutralization capacity of limestones for horticultural container substrate use. Limestone samples from 20 North American quarries were analyzed for CaCO3 and MgCO3 content and were each wet-sieved into eight particle diameter fractions from 600 to < 38 microns (passing through 30 to 400 mesh U. S. Standard screens). The surface area of each fraction was measured using the Monosorb Surface Area Analyzer (Quantachrome, Corp., Boynton Beach, FL) utilizing the BET theories. As expected, for all limestone sources the coarsest particles had smaller SSA than the finest particles. Eight of the twenty sources had increasingly larger SSA as particle diameter
decreased. The remaining sources exhibited a decrease in SSA from the coarsest particles to around the 170-200 mesh screen size particle fraction. As particle diameter decreased further SSA increased. It is probable that the larger limestone particles contained internal pores sensed by the surface area analyzer. Smaller particles may have occurred due to breakage along the axes of these internal pores causing a reduction in SSA. There was a 74-fold difference in SSA in the coarsest particle category across the 20 sources. With decreasing particle size this differential decreased to 20 fold in the finest particle size. The weak relationship between particle size and SSA explains the poor capacity of particle size for predicting limestone neutralization capacity. SSA appears to be a beter predictor, however it is a tedious procedure. There was a weak inverse correlation between SSA and proportion of Mg relative to Ca; however, this relationship was not strong enough for Mg percentage to
replace SSA.
Impacts
These results pave the way for soilless substrate formulators to measure the neutralization requirement of individual substrates or components and to determine the neutralization capacity of individual lots of limestone. The two pools of data will be used to match limestone with substrate more accurately than is currently possible with the resulting benefit of more precise achievement of target pH. This has been a major problem for growers and formulators of soilless substrate.
Publications
- Rippy, J.F.M., Peet, M.M., Louws, F.J., Nelson, P.V., Orr, D.B. and Sorensen, K.A. 2004. Plant development and harvest yields of greenhouse tomatoes in six organic growing systems. HortScience 39(2):223-229.
- Nelson, P.V., Oh, Y.M. and Cassel, D.K. 2004. Changes in physical properties of coir dust substrates during crop production. Acta Horticulturae 644:261-268.
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Progress 10/01/02 to 09/30/03
Outputs
Procedural parameters were developed for titrating sphagnum peat moss for purposes of determining its neutralization requirements. A moisture content of 95% of container capacity was found to be as effective as higher levels of 100, 120, and 150% for bringing base into contact with peat moss. Equal equivalent levels of Ca(OH)2 resulted in lower rises in peat moss pH compared to NaOH. This indicated a higher affinity of the cation exchange sites of peat moss for Ca and thus a preference to use Ca(OH)2 as the titrant for agricultural applications of the data. Titration with either base resulted in an initial high rise in pH followed by a decline to a stable level. Time to equilibrium was shortened by addition of CaSO4. Peat moss pH was lower with CaSO4 in the ranges around 4 and 8 but not between indicating that it is not necessary for a titration curve within the pH range of crop production. Twenty four hours contact between base and peat moss was sufficient to reach
equilibrium with and without CaSO4. Samples of limestone were collected from 40 quarries across North America for purposes of identifying parameters to be used in predicting neutralization capacity for soilless substrate application. Data was collected for each source including hardness (LA abrasion test), weatherability (magnesium sulfate test), calcium/magnesium ratio, internal porosity, and specific gravity. Three sources were sieved into 10 particle size ranges from 16 to 30 to less than 635 mesh. Surface area was measured for each fraction using a Quantachrome Monosorb Surface Area Analyzer with N2 as the absorbate. The ratio of particle diameter to surface area varied among limestone sources suggesting that surface area would be a better predictor of neutralization value.
Impacts
These results pave the way for soilless substrate formulators to measusre the neutralization requirement of individual substrates or components and to determine the neutralization capacity of individual lots of limestone. The two pools of data will be used to match limestone with substrate more accurately than is currently possible with the resulting benefit of more precise achievement of target pH. This has been a major problem for growers and formulators of soilless substrate.
Publications
- Davis, J.M., Sanders, D.C., Nelson, P.V., Lengnick, L., and Sperry, W.J. 2003. Boron improves growth, yield, quality, and nutrient content of tomato. J. Amer. Soc. Hort. Sci. 128(3):441-446.
- Nelson, P.V., Kowalczyk, W., Niedziela, Jr., C.E., Mingis, N.C., and Swallow, W.H. 2003. Effects of relative humidity, calcium supply, and forcing season on tulip calcium status during hydroponic forcing. Scientia Horticulturae. 98(4):409-422.
- Nelson, P.V. 2003. Greenhouse operation and management. 6th edition. Prentice-Hall, Inc., Upper Saddle River, NJ 692 pp.
- Whipker, B.E., Cavins, T.J., Gibson, J.L., Dole, J.M., Nelson, P.V., and Fonteno, W.C. 2003. Plant Nutrition. In: V. Ball (ed.). Ball Red Book, 17th. Edition. Ball Publishing, St. Charles, IL.
- Whipker, B.E., Cavins, T.J., Gibson, J.L., Dole, J.M., Nelson, P.V., and Fonteno, W.C. 2003. Water, media, and nutrition testing. In: V. Ball (ed.). Ball Red Book, 17th. Edition. Ball Publishing, St. Charles, IL.
- Whipker, B.E., Nelson, P.V., Dole, J.M., Williams, A.L., Gibson, J.L., Walls, F.R., and Cleveland, B.R. 2003. Nutrient deficiencies of pepper. GM-PRO 23(1):34-37.
- Nelson, P.V., Dole, J.M., Williams, A.L., Whipker, B.E., Walls, F.R., and Cleveland, B.R. 2003. Nutrient deficiencies of Brachycome 'Jumbo Mauve'. GM-PRO 23(2):30-34.
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