Jeffrey C Silvertooth

Interests

Research

The program has been directed towards the development of crop production management strategies (primarily irrigated cotton, chiles, cantaloupes, and leafy green winter vegetables) that optimize the soil-plant system agronomically and economically, with full consideration of the short- and long-term impact of inputs environmentally. Studies of the soil-plant relationships, particularly regarding nutrient and water requirements for cotton, chiles (New Mexico type), and cantaloupes have been principle areas of operation for the program. Salinity and sodicity management in agricultural soils are consistent and important aspects of the program. The overall goal in terms of managing irrigated crop production systems, by interacting and collaborating with other programs, is to reduce the level of inputs such as pesticides, fertilizers, and irrigation water; and maintain profitability and sustainability in both the short- and long-term agricultural production systems in the desert Southwest.

Courses

Scholarly Contributions

Journals/Publications

• Bronson, K. F., Norton, E. R., & Silvertooth, J. C. (2021). Revising Petiole Nitrate Sufficiency/Deficiency Guidelines for Irrigated Cotton in the Desert Southwest.. Soil Sci Soc Am J. 2021; 85:893-902., 85, 893-902.
• Bronson, K. F., Silvertooth, J. C., & Norton, E. R. (2021). Revising Petiole Nitrate Sufficiency/Deficiency Guidelines for Irrigated Cotton in the Desert Southwest.. Soil Sci Soc Am J., 85, 893-902.
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  Petiole NO3 sampling and testing remains a popular in-season N management practice in the Western US for cotton (Gossypium hirsutum). However, the present guidelines used by Arizona are > 35 years old and are in need of updating. The objectives of this study were to relate in-season petiole NO3 levels with lint yields and revise the former critical deficiency levels by growth stage guidelines. We sampled petioles between first square and peak bloom in nine site-years of cotton N management field trials in Maricopa and Safford, AZ from 2014-2108. Irrigation type in Maricopa was overhead sprinkler (OSI) (2014-2015), and subsurface drip irrigation (SDI) (2016-2018). In Safford (2014-2017), surface irrigation (SI) was used. Petiole NO3 in SDI was dramatically lower than with SI or OSI, mostly in the deficient range. Lower lint yields in zero-N treatments compared to pre-plant soil NO3 test-based reference treatments occurred in 8 site-years (Safford 2016 crop lost to hail), and were considered N deficient. Critical petiole NO3 levels from 1984 were revised downward 1g N kg-1, since several N-fertilized plot means of petiole NO3 were in that range and did not exhibit an N rate-related yield depression. Petiole nitrate concentrations before first bloom did not reliably indicate N deficiency or separate N-deficient from N-sufficient treatments.
• Bronson, K. F., Norton, E. R., & Silvertooth, J. C. (2020). Revising petiole nitrate sufficiency/deficiency guidelines for irrigated cotton in the Desert Southwest. Soil Science Society of America Journal, 85(3), 893-902. doi:10.1002/saj2.20213
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  Petiole nitrate-nitrogen (NO3–N) sampling and testing remains a popular in-season nitrogen (N) management practice in the western United States for cotton (Gossypium hirsutum L.). However, the present guidelines used by Arizona are greater than 35 yr old and are in need of updating. The objectives of this study were to relate in-season petiole NO3 levels with lint yields and N deficiencies and to revise the former critical deficiency level guidelines by growth stage. Petioles were sampled between first square and peak bloom in nine site-years of cotton N management field trials in Maricopa and Safford, AZ, from 2014 to 2018. Irrigation type in Maricopa was overhead sprinkler irrigation (OSI) (2014–2015) and subsurface drip irrigation (SDI) (2016–2018). In Safford (2014–2017), surface irrigation (SI) was used. Petiole NO3 in SDI was dramatically lower than with SI or OSI, mostly in the deficient range. Lower lint yields in zero-N treatments compared with pre-plant soil NO3 test–based reference treatments occurred in eight site-years (Safford 2016 crop lost to late hailstorm) and were considered N deficient. Critical petiole NO3–N levels from 1984 were revised downward 1 g N kg−1 because several N-fertilized treatment means of petiole NO3 were in that range and did not exhibit an N rate–related yield depression. Sampling cotton plants for petiole NO3 analysis should start within 1 wk of first bloom. Petiole NO3 dynamics and critical levels in SDI cotton required further study.
• Babcock, E. L., & Silvertooth, J. C. (2012). Soil Testing and Plant Analysis Relationships for Irrigated Chile Production. Communications in Soil Science and Plant Analysis, 43(20), 2651-2668.
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  Abstract: In a field study of irrigated chile (Capsicum annum L.) production in southeastern Arizona and southwestern New Mexico from 2008 through 2009, soil and tissue test samples were analyzed for a spectrum of plant nutrients at 16 different sites, including nitrogen (N), phosphorus (P), potassium (K), zinc (Zn), iron (Fe), and boron (B). The objectives were to evaluate soil and tissue nutrient testing procedures and to establish basic soil and plant tissue-testing guidelines and recommendations with respect to yield potentials. Soil samples were collected before planting. Plant tissue samples from plots at all sites were collected at the following four stages of growth: first bloom (FB), early bloom (EB), peak bloom (PB), and physiological maturity (PM). Fertilizer and nutrient inputs were monitored, managed, and recorded within current extension guidelines for irrigated chiles. Results for soil and tissue analyses were compared to yield results. The results provide estimates for baselines, which can be tested through subsequent calibration experiments to establish recommendations for critical soil- and tissue-test values. Absolute minimum soil-test nutrient values were identified as 10 parts per million (ppm) P, 110 ppm K, 0.3 ppm Zn, 2.0 ppm Fe, and 0.25 ppm B. Absolute minimum FB leaf tissue test values were 0.2% P, 4.5% K, 10 ppm Zn, 80 ppm Fe, and 30 ppm B. Complete data sets for leaf and petiole tissue-test values for all stages of growth were collected. These soil-test and plant nutrient values will be evaluated in subsequent experiments to better define fertilizer nutrient inputs and to gain better nutrient-management efficiencies in irrigated chile production systems. © 2012 Copyright Taylor and Francis Group, LLC.
• Silvertooth, J., Bronson, K., Norton, E., & Mikkelsen, R. (2011). Nitrogen Utilization by Western U.S. Cotton. Better Crops, 2, 21-23.
• Norton, E. R., & Silvertooth, J. C. (2008). Nitrogen volatilization from Arizona irrigation waters. Communications in Soil Science and Plant Analysis, 39(15-16), 2378-2397.
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  Abstract: A laboratory study was initiated to investigate the effects of temperature (25, 30, 35, and 40°C) and water quality on the loss of fertilizer nitrogen (N) through volatilization out of irrigation waters collected from 10 different Arizona sources. A 300-mL volume of each water source was placed in 450-mL beakers open to the atmosphere in a constant-temperature water bath with 10 mg of analytical-grade ammonium sulfate [(NH4)2SO4] dissolved into each sample. Small aliquots were drawn at specific time intervals over a 24-h period and then analyzed for ammonium (NH4 +)-N and nitrate (NO3 -)-N concentrations. Results showed potential losses from volatilization to be highly temperature dependent. Total losses (after 24 h) ranged from 30-48% at 25°C to more than 90% at 40°C. Volatilization loss of fertilizer N from irrigation waters was found to be significant and should be considered when making decisions regarding fertilizer N applications for crop production in Arizona particularly when using ammonia-based fertilizers. Copyright © Taylor & Francis Group, LLC.
• Silvertooth, J. C., & Soto-ortiz, R. (2008). A Crop Phenology Model for Irrigated New Mexico Chile (Capsicum annuum L.) Type Varieties. Vegetable Report.
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  Field experiments were conducted with the objective of developing a general New Mexico chile type plant (Capsicum annuum L.) phenological model as a function of heat units accumulated after planting (HUAP). Field experiments were conducted from 2003 through 2005 in the Sulfur Springs Valley of Arizona, near Sunsites in Cochise County, Arizona (31 o 56” N, 109 o 52” W, about 4,000 feet elevation) on a Borderline fine sandy loam (coarseloamy, mixed, superactive thermic Typic Calcigypsids) and in the Animas Valley, New Mexico (31 o 57” N, 109 o 48” W, about 4,400 feet elevation), on a Vekol fine sandy clay loam (fine, mixed, thermic, Typic Haplargids). Plant measurements were collected routinely and important phenological stages that corresponded to first bloom, early bloom, peak bloom, physiological maturity, and red harvest were identified and recorded. Results indicate that within locations, all varieties performed similarly in relation to HU accumulation patterns. A general New Mexico chile type plant phenological model as a function of HUAP for all sites and varieties was obtained. First bloom occurred at 954 ± 254 HUAP, early bloom at 1349 ± 306 HUAP, peak bloom at 1810 ± 261 HUAP, physiological maturity at 2393 ± 215 HUAP, and red chile harvest was identified to occur at 3159 ± 220 HUAP. The purpose of this phenological baseline or model is to provide a crop management tool for growers for predicting and identifying critical stages of growth. Further development and validation of this model is a continued objective of this research program.
• Silvertooth, J. C., & Soto-ortiz, R. (2008). Crop Phenology for Irrigated Spring Cantaloupes (Cucumis melo L.). Vegetable Report.
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  Field experiments were conducted in 2007 to evaluate a cantaloupe (Cucumis melo L.) plant development model as a function of heat units accumulated after planting (HUAP). Field experiments were conducted in 2007 in the Yuma Valley, Arizona (32 o 42’ N, 114 o 42’ W), about 150 feet (~ 32 m) elevation in four commercial cantaloupe fields managed by a cooperator-grower using four varieties. Plant measurements were made on regular 14-day intervals and the following growth stages were identified in relation to plant measurement data collection: pre-bloom, early fruit set, early netting, and physiological maturity (harvest). The model was evaluated by comparing the observed HUAP versus the predicted HUAP values using a repeated measures design. Mean differences within each sampling stage were separated using the Fishers’ protected least significance difference (LSD) test at P≤ 0.01. In addition, regression models were performed for all in-season data collected and the accuracy of the model was evaluated on the basis of the R 2 values with a specified level significance (α = 0.01). No statistical differences were found between the observed phenological data and the predicted values from the model throughout the study period. Also, the model presented an overall accuracy of 54 ± 37 HUAP (2 ± 1 day) in predicting cantaloupe-harvesting time. It can be concluded that the model can be used as a useful tool to assist cantaloupe growers in predicting and identifying critical stages of growth for irrigated spring cantaloupe crops in Arizona and the desert Southwest.
• Norton, E. R., & Silvertooth, J. C. (2007). Evaluation of added nitrogen interaction effects on recovery efficiency in irrigated cotton. Soil Science, 172(12), 983-991.
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  Abstract: Studies were conducted in 1997 and 1999 at the University of Arizona Maricopa Agricultural Center to evaluate the added nitrogen (N) interaction or 'priming effect' on the determination of N recovery efficiencies (NRE) in Upland cotton (Gossypium hirsutum L.). Overall growth patterns of the crop were significantly different between the two years. In 1997, the crop experienced a favorable balance between reproductive and vegetative growth. The NRE estimates were 34.7% and 34.7% for Treatment 1 (recommended fertilizer N rate, 168 kg N ha (RecN)) and 25.2% and 26.0% for Treatment 2 (twice recommended fertilizer N rate, 336 kg N ha (RecN 2×)) for the difference and isotopic dilution technique, respectively. In 1999, however, the crop experienced very poor fruit load and vigorous vegetative growth. This resulted in a crop that produced much more vegetative dry matter at the expense of reproductive dry matter (yield). Higher NRE estimates were observed using the difference technique (50.8% and 40.5% for RecN and RecN 2×, respectively) when compared with the isotopic dilution technique (32.3% and 35.2% for RecN and RecN 2×, respectively). Higher amounts of soil N taken up by the plant were also observed in 1999 when compared with those in 1997. The results presented from these studies indicate that plant uptake of indigenous soil N was much higher in 1999 than in 1997, which is evidence of an added N interaction. However, this increase does not seem to have been stimulated by the addition of fertilizer N but rather the increased vegetative growth and root exploration that occurred in 1999. © 2007 Lippincott Williams & Wilkins, Inc.
• Galadima, A., Silvertooth, J. C., & Soto-ortiz, R. (2006). Cantaloupe Response to CN9™ Fertilizer. Vegetable Report.
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  Field experiments were conducted at four sites in 2005 in the Yuma Valley, AZ (approximately 150 ft. elevation) to evaluate the performance of CN9 fertilizer [a N-calcium (Ca) based fertilizer (9-0-0-11)] in comparison to a conventional N fertilizer source with irrigated melons/cantaloupes (Cucumis melo L.). Each field was divided into two equal (approximately 40 acres) sections. One section received the grower’s N fertilizer source (Conventional) while the other section received the CN9 fertilizer. Basic plant growth and development measurements, aboveground biomass, total and marketable yield, Sugar fruit content as well as total nutrient analysis were among the main variables analyzed. In general, all phenology variables responded similarly between conventional and CN9 treatments. Fresh weight yields ranging from 4,000 to 10,000 kg/ha were observed between conventional and CN9 treatments. Statistical analyses show that total yield between conventional and CN9 was statistically the same; with the exception of the Perriconi site. Similar results were observed for marketable yield. Brix values ranged from 10 to 14 percent, statistical differences for Brix values between the conventional and CN9 treatments were found on the Perriconi and Mason 80 sites where the conventional treatment had higher sugar content in the fruit. Overall, there were no differences in nutrient uptake and allocation patterns due to the addition of CN9 among experimental sites or sampling dates. Regarding the allocation of nutrients in the rind and flesh of melons, the same patterns between treatments at all sites were observed.
• Galadima, A., Silvertooth, J. C., & Soto-ortiz, R. (2006). Crop Phenology for Irrigated Chiles (Capsicum annuum L.) in Arizona and New Mexico. Vegetable Report.
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  To determine growth and development patterns of irrigated green chile plants as a function of heat units accumulated after planting (HUAP), as well as to develop a general irrigated chile plant development model as a function of HUAP. Field experiments were conducted in 2004 and 20055 at Sunsites in Cochise County, AZ (about 4,000 ft. elevation) and at the Massey Farm in the Animas Valley, NM (about 4,392 ft. elevation). Basic plant growth and development measurements were collected routinely and important phenological stages that corresponded to first bloom, early bloom, peak bloom, physiological maturity, and red harvest were identified and recorded. Results indicate that among all sites, all varieties have performed similarly in relation to HU accumulation patterns and preliminary plant phenology models are under development in this program. The primary difference between sites was that at Sunsites varieties tend to reach a 50/50 (green: red chile) ratio at 2900 HUAP and for Animas valley; this same ratio was reached at 3200 HUAP. Also, a general irrigated green chile plant development model as a function of HUAP for all sites and varieties was obtained. The purpose of this phenological baseline or model is to assist growers in predicting and identifying critical stages of growth for crop management purposes. First bloom occurred at 1369 ± 72 HUAP, early bloom at 1667 ± 79 HUAP, peak bloom at 1998 ± 84 HUAP; physiological maturity at 2285 ± 159 HUAP, and red chile harvest was identified to occur at 3295 ± 216 HUAP.
• Hunsaker, D. J., Pinter Jr., P. J., Clarke, T. R., Fitzgerald, G. J., Kimball, B. A., Barnes, E. M., Silvertooth, J. C., & Hagler, J. (2004). Scheduling cotton irrigations using remotely-sensed basal crop coefficients and FAO-56. ASAE Annual International Meeting 2004, 1931-1944.
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  Abstract: Techniques to more accurately quantify crop evapotranspiration (ET C) are needed for determining crop water needs and appropriate irrigation scheduling. In this study, remotely sensed observations of the normalized difference vegetation index (NDVI) were used to estimate cotton basal crop coefficients (Kcb), which were then applied within the dual crop coefficient procedures of the Food and Agricultural Organization (FAO), Paper 56 (FAO-56) to calculate daily ETC. An experiment in central Arizona during 2003 compared irrigation scheduling using a remotely sensed Kcb technique (NDVI treatment) with the FAO-56 Kcb curve (FAO treatment). The FAO curve was locally developed for optimum crop conditions and standard cotton density. Final lint yield means were not significantly different between the two irrigation methods, which included sub-treatments of two levels of nitrogen and three plant densities. However, NDVI attained higher yields under low N input, whereas FAO generally had higher yields under high N. The ETC estimated using the NDVI-KCb method was in closer agreement with measured cumulative ETC than the FAO Kcb. For high N treatments, the mean absolute differences between measured and estimated cumulative ETC during the growing season for typical, dense, and sparse populations (10, 20, and 5 plants m-2, respectively) were 4, 17, and 4 mm, respectively, for NDVI, whereas they were10, 32, and 13 mm, respectively, for FAO. Although additional research is needed for improving our remote sensing technique, it potentially offers an improvement over the FAO Kcb curve for quantifying actual ETC.
• Husman, S., Silvertooth, J. C., & Tronstad, R. (2003). Irrigation Termination of Cotton: An Economic Analysis of Yield, Quality, and Market Factors. Journal of cotton science, 7(3), 86-94.
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  The decision to terminate the irrigation of cotton (Gossypium hirsutum L.) is complicated by interactions and uncertainties related to lint yield and quality, water costs, and market factors. High, medium, and low values for the cost of water, lint price, and quality discount/premium schedule for High Volume Instrument (HVI) quality factors were applied to lint yield and quality differentials realized from irrigation termination experiments conducted in central Arizona for the crop years of 1991 and 1992, 1994 through 1997, and 2000. Deviations in lint yield and quality for the first irrigation termination treatment versus the subsequent second and third irrigation termination treatments are the agronomic basis of this study. Irrigation termination dates were defined by heat units after planting (31/12.8o C or 86/55o F) to place the crop progression of different experimental sites and years on a more equal basis than using calendar dates. Classification and regression tree analysis was used to quantify the data. The relative ranking of results from this procedure in which the most important variable is normalized on 100 were as follows: cultivar (100), additional heat units after the first irrigation termination treatment (94), yield of first irrigation termination treatment trial (93), year of the field experiment or crop year (83), micronaire associated with the first irrigation termination treatment (68), heat units after planting for the first irrigation termination treatment (67), lint price (5), water cost (2), and the quality discount/premium year (0.09). In general, the season needs to be extended at least 330 to 360 heat units Centigrade (600 to 650 heat units Fahrenheit) to yield a profitable return for cultivars with potential to produce a top-crop. Also, a crop that has a yield less than 1533 kg ha -1 (1368 lb ac -1 ) at the first irrigation termination treatment is more likely to have the potential for producing a profitable top-crop than a crop that has already set a fruit boll load greater than this level.
• Tronstad, R., Silvertooth, J., & Husman, S. (2003). Irrigation termination of cotton: An economic analysis of yield, quality, and market factors. Journal of Cotton Science, 7(3).
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  The decision to terminate the irrigation of cotton (Gossypium hirsutum L.) is complicated by interactions and uncertainties related to lint yield and quality, water costs, and market factors. High, medium, and low values for the cost of water, lint price, and quality discount/premium schedule for High Volume Instrument (HVI) quality factors were applied to lint yield and quality differentials realized from irrigation termination experiments conducted in central Arizona for the crop years of 1991 and 1992, 1994 through 1997, and 2000. Deviations in lint yield and quality for the first irrigation termination treatment versus the subsequent second and third irrigation termination treatments are the agronomic basis of this study. Irrigation termination dates were defined by heat units after planting (31/12.8° C or 86/55° F) to place the crop progression of different experimental sites and years on a more equal basis than using calendar dates. Classification and regression tree analysis was used to quantify the data. The relative ranking of results from this procedure in which the most important variable is normalized on 100 were as follows: cultivar (100), additional heat units after the first irrigation termination treatment (94), yield of first irrigation termination treatment trial (93), year of the field experiment or crop year (83), micronaire associated with the first irrigation termination treatment (68), heat units after planting for the first irrigation termination treatment (67), lint price (5), water cost (2), and the quality discount/premium year (0.09). In general, the season needs to be extended at least 330 to 360 heat units Centigrade (600 to 650 heat units Fahrenheit) to yield a profitable return for cultivars with potential to produce a top-crop. Also, a crop that has a yield less than 1533 kg ha-1 (1368 lb ac-1) at the first irrigation termination treatment is more likely to have the potential for producing a profitable top-crop than a crop that has already set a fruit boll load greater than this level. © The Cotton Foundation 2003.
• Navarro, J. C., Norton, E. R., Sanchez, C. A., & Silvertooth, J. C. (2001). Evaluation of a NITROGEN-15 microplot design in furrow-irrigated cotton. Soil Science Society of America Journal, 65(1), 247-250. doi:10.2136/sssaj2001.651247x
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  Information is needed regarding an appropriate microplot design for use in furrow-irrigated row crop systems. Field experiments were conducted at two locations in Arizona, Maricopa in 1991 (Casa Grande sandy loam) and Marana in 1995 (Pima clay loam). The purposes of the experiments were to evaluate the dimensions of an 15 N microplot design used in a furrow irrigated row crop system. The experiments each utilized ammonium sulfate fertilizer with 5 atom% N enrichment applied at a rate of 56 kg N/ha in a simulated side-dress band application during the early bloom stage of development of Upland cotton (Gossypium hirsutum L.). At each location, microplots were four, 1.02-m rows wide and 1.00 m in length. Whole plant samples were collected at specific locations within and near the microplots. Collection of plant materials at a minimum distance of 25 cm from the microplot borders provided uniform 15 N enrichment levels for determining fertilizer N uptake and recovery. Microplots with the dimensions of those used in this study are sufficient for collecting plant materials from a 1-m 2 area, consisting of two, 50-cm segments from the interior two rows of the four row microplot.
• Galadima, A., Sanchez, C. A., & Silvertooth, J. C. (2000). 538 Understanding Why Horticultural Crops in the Desert Rarely Respond to K Fertilization. Hortscience, 35(3), 488-488. doi:10.21273/hortsci.35.3.488c
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  Vegetable and fruit crops produced in the desert southwestern United States generally do not respond to K fertilization. Even when pre-plant soil test K levels are low and crop K accumulations are high, responses are infrequent. We have performed a number of evaluations aimed at understanding why crops produced in this region fail to respond to K fertilization. First, data show the potential for substantial K inputs through irrigation. For example, Colorado River water, which is widely used for irrigation in this region, contains ≈5 ppm K, resulting in potential K inputs of 30 to 60 kg K/ha. Second, many of the soils used for crop production have a clay content and mineralogy making a response to K unlikely. Studies evaluating the kinetics of K release from the mineral fraction of soils in the region has shown that many soils used for crop production have a high capacity to replenish K to the soil solution and exchange sites following crop uptake. Finally, the observation that Na can partially substitute for the K requirement of many fast-growing leafy vegetables may also be a contributing factor for the infrequent K fertilizer responses for these commodities.
• May, L., Brown, S., Nichols, B., Kerby, T., & Silvertooth, J. (2000). Proposed guidelines for pre-commercial evaluation of transgenic and conventional cotton cultivars. 2000 Proceedings Beltwide Cotton Conferences, 503-507.
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  Abstract: The primary, commercial features of the recently-released, transgenic cotton cultivars are their respective pest management traits, including, tolerance to the herbicides Buctril® (bromoxynil) and Roundup Ultra® (glyphosate), and the capacity to synthesize a bacterial endotoxin Bacillus thuringiensis (Bt) for management of lepidopterous in pests. Many transgenic cultivars have been offered for sale with fewer years of public testing than most growers and their advisors would have liked. Lack of time and resources may have resulted in some having been sold in locations with no previous public testing in the immediate growing area. Despite the lack of public test-information, the collective market share of the transgenic cultivars has increased every year since their introduction, presumably because of high grower interest in their value-added, pest-management features. Obviously, transgenic pest management traits strongly influence the pest management programs that are appropriate for the transgenic cultivars, and the efficacy of the pest management programs may positively affect yields and the costs of production. However, in the Official Cultivar Trials (OCTs), comparison of the transgenic cultivars with non-transgenic (conventional) cultivars has been done using only conventional, and frequently, a high-level of pest management. Concerns, about the lack of public-test data on transgenic cultivars, and about relying solely on OCTs for their evaluation, prompted Cotton Incorporated to convene a working group (Appendix I.). The objective was to seek consensus among public and private sector researchers on how to enable growers to confidently choose the best cultivar and pest-management technology for their situation. The drafting subcommittee of the working group proposed guidelines for cultivar evaluation to a joint meeting of SRIEG-61 (Southern Regional Information Exchange Group 61 - Cotton Breeding), and a new Regional Project in preparation, SRDC-9801, (Southern Regional Development Committee 9801 - Development of Genetic Resources for Cotton). Principal points of the proposal were that a minimum of two years of public test data should be available to growers at the time of first sale, and that the data should include comparison of transgenic cultivars with cultivars generally recognized as having high-yield potential. The proposal also suggested that the testing should provide comprehensive economic evaluation of new cultivars by concurrently evaluating yields, fiber quality, and the efficacy and costs of the respective pest management programs.
• Moser, H. S., McCloskey, W. B., & Silvertooth, J. C. (2000). Performance of transgenic cotton varieties in Arizona. 2000 Proceedings Beltwide Cotton Conferences, 497-499.
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  Abstract: The purpose of this test was to evaluate the performance of transgenic cotton varieties in Arizona. We conducted four field tests at three Arizona locations in 1999. We included a total of 34 varieties in one or more of these tests. Across locations and varieties, Bollgard (BG) and stacked (BGRR) varieties produced about 7 to 8% greater lint yields than the conventional varieties. Roundup Ready (RR) varieties produced similar lint yields as the conventional varieties. A few transgenic varieties were lower yielding than the conventional parent in these tests. Roundup Ready varieties tended to be taller and more vigorous than the conventional parent. Transgenic varieties were sometimes different from the conventional parent in other traits, such as lint percent, boll weight, or maturity, but the variation was not associated with a particular transgene.
• Silvertooth, J. C., & Norton, E. R. (1999). Environmental considerations for cotton fertilization. Proceedings of the 1999 Beltwide Cotton Conference, January, 1999, Orlando, Florida, USA, 29-31.
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  Abstract: Cotton (Gossypium spp.) fertilization is conducted primarily with agronomic objectives. These objectives are commonly oriented toward optimizing lint yield and quality by maintaining good plant nutrition and health. Economic objectives are also often considered in terms of optimizing the return on the investment (lint production in relation to dollars expended on crop fertilization). Another set of considerations that are important in the fertilization of a cotton crop is that of environmental impacts. Cotton is a dynamic crop with respect to growth and yield, and therefore, the management of the vegetative/reproductive balance is very important. Accordingly, crop fertilization is important in relation to managing crop vigor and yield potential. The nutrients that are most susceptible to having a negative impact on the environment are those that are mobile in the soil system such as nitrogen (N) and sulfur (S). There is experimental evidence that crop fertilization can be managed so that agronomic, economic, and environmental efficiencies can be optimized simultaneously. Efficient crop fertilization needs to take into account the soil fertility levels for a given field, in-season crop conditions (e.g. fruit retention, vigor, and fertility status), stage of growth, and crop-specific nutrient demand characteristics. Providing applications of appropriate nutrients in-season can provide a good means of maintaining plant nutrition and fertilizer efficiencies.
• Unruh, B. L., & Silvertooth, J. C. (1999). Cotton monitoring for in-season management decisions in far west Texas. Proceedings of the 1999 Beltwide Cotton Conference, January, 1999, Orlando, Florida, USA, 632-634.
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  Abstract: Cotton (Gossypium spp.) produced under fully-irrigated conditions in the Desert Southwest is expensive and management intensive, having many factors that affect cotton growth and development throughout the growing season. Therefore, many in-season decisions need to be made in a timely fashion, which can greatly affect final yield. Cotton monitoring assists producers make informed in-season management decisions: Presented here, is a method of taking simple plant measurements and graphing trends of plant growth and development against standard curves to identify if the crop is developing correctly. The standard curves include upper and lower thresholds, so that 'normal' growth and development can be easily identified. Trends that cross the thresholds indicate an abnormal situation, which requires a management correction. The standard curves used in this system were developed in the Desert Southwest under environmental conditions similar to the Trans-Pecos region of Texas (Silvertooth, 1994).
• Brown, P. W., Silvertooth, J. C., & Steger, A. J. (1998). Upland cotton growth and yield response to timing the initial postplant irrigation. Agronomy Journal, 90(4), 455-461. doi:10.2134/agronj1998.00021962009000040002x
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  Cotton (Gossypium spp.) production in arid and semiarid regions depends on well-managed irrigation systems for optimum yield and production efficiency. Water deficit stress early in the growing season can affect the subsequent growth and development of short-season cotton. A 2-yr field study was conducted in southern Arizona to determine the optimum timing of the initial postplant irrigation for a short-season upland cotton variety based on midday leaf water potential (LWP) measurements, and to evaluate the season-long effects of delayed irrigation on subsequent plant growth patterns. In both years, the short-season upland variety, DPL 20, was planted into a Pima clay loam soil [fine-silty, mixed (calcareous), thermic Typic Torrifluvent] that had received a preplant irrigation of 152 (1993) or 254 mm (1994) approximately 3 wk prior to planting. Treatments, designated T1, T2, and T3, received the initial postplant irrigation when the average midday LWP of the uppermost, fully expanded leaf measured -1.5, -1.9, and -2.3 MPa, respectively. Daily midday LWP measurements were taken using the pressure chamber technique. Soil water was measured at 25-cm depth increments using neutron attenuation. Plant height, number of mainstem nodes, nodes above white flower (NAWF), and canopy closure were measured at weekly intervals. All treatments reached maturity, as measured by NAWF ≤ 5, at approximately the same time during the growing season. Complete canopy closure was delayed in the T3 plots resulting in reduced interception and utilization of available solar radiation early in the growing season. When treatments were initiated, approximately 84% (T1), 62% (T2), and 32% (T3) of the total plant-available water (field capacity less permanent wilting point) was present in the upper 1.5 m of the soil profile. Yields were 1263, 1244, and 1110 kg lint ha -1 in 1993 and 1229, 1176, and 1095 kg lint ha -1 in 1994 for T1, T2, and T3, respectively. Lint yields were significantly different in 1993 (P = 0.001), indicating that timing the initial postplant irrigation affected plant growth and lint yield potential.
• Griffin, J. R., Silvertooth, J. C., & Norton, E. R. (1998). Evaluation of calcium soil conditioners in an irrigated cotton production system. Proceedings of the 1998 beltwide cotton conferences, San Diego, CA, USA, January 5-9 1999, 645-648.
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  Abstract: In 1996 a single field experiment was conducted at Paloma Ranch, west of Gila Bend in Maricopa County Arizona. Nucoton 33B was dry planted and watered-up on 15 April. Treatments consisted of various rates and times of application of nitrogen (N) and calcium (Ca) from two sources (N-Cal TM and CAN TM-17), as well as a standard N source, UAN-32, along with a Ca check, which received no Ca. Treatments 1, 2, and 3 each received a total of 280 lbs. N/acre. Treatment 4 received a total of 210 lbs. N/acre while treatment 5 received a total of 301 lbs. N/acre. Treatment 1 was a standard for reference and received only applications of UAN-32. Treatments 2 and 4 each received a total of 72 lbs. of Ca/acre. Treatment 5 is the same as treatment 2 except that it received a total of 79 lbs. Ca/acre that included a 7 lbs. Ca/acre at water up. Treatment 3 received a total of 300 lbs. Ca/acre. No significant differences were found among the various treatments in terms of plant growth, soil water content, EC(e) values, and sodium absorption ratios. Lint yields were significantly different (P
• Norton, E. R., & Silvertooth, J. C. (1998). Field validation of soil solute profiles in irrigated cotton. Agronomy Journal, 90(5), 623-630.
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  Abstract: Management of water and fertilizer N are important aspects of cotton production in the desert Southwest. GOSSYM, a cotton growth simulation model, has been used extensively to manage these inputs. Our objectives were to further validate GOSSYM by comparing model-simulated and measured soil NO3/--N profiles, to evaluate GOSSYM's potential as a management tool under irrigated growing conditions in the desert part of the U.S. Cotton Belt, and to address questions about the way GOSSYM simulates NO3/--N movement through the soil profile in relation to irrigation water management (which in turn affects prediction of plant growth and development). We compared measured profiles of NO3--N with GOSSYM-simulated profiles. Soil profile samples were obtained from an existing N-management field study, a split-plot within a randomized complete block design. Mainplots were upland and pima cotton (G. hirsutum L. cv. DPL 5415 and G. barbadense L. cv. Pima S-7, respectively). Subplots were a check (0 fertilizer N) and three other N-management strategies. The cotton was grown on a Casa Grande sandy loam [fine-loamy, mixed, hyperthermic Typic Natrargid (reclaimed)] near Maricopa, AZ, in 1994 and 1995. Fertilizer N rates ranged from 0 to 350 kg ha-1 in 1994 and 0 to 392 kg ha-1 in 1995. Soil samples taken to a depth of 120 cm in 30-cm increments were analyzed for NO3/--N. Comparisons of simulated and actual NO3/--N profiles revealed tendencies in GOSSYM to overestimate NO3/--N leaching out of the effective rooting zone, resulting in simulated N stresses midseason. When GOSSYM simulated an N stress, between 50 and 75% of the simulated soil NO3/--N values were greater than the measured values, yet the simulated N stress still occurred. This indicates possible limitations in GOSSYM's ability to adequately predict N uptake by plants. The dynamic soil N portion of the model needs further refinement, particularly for cotton production under irrigated desert conditions.
• Norton, E. R., & Silvertooth, J. C. (1998). The University of Arizona cotton monitoringsystem. Proceedings of the 1998 beltwide cotton conferences, San Diego, CA, USA, January 5-9 1999, 103-.
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  Abstract: Cotton production in the desert Southwest is commonly characterized by a high input system oriented toward high yields. Water is commonly the first, most limiting factor in desert cotton production systems. Other important inputs include pest control, fertilizer nitrogen (N), and plant growth regulators. Since cotton is very responsive to crop inputs, such as water and fertilizer N, management of these factors is critical to achieve not only maximum agronomic, but also economic yield. Efficient management of all inputs is extremely important for crop management and realizing a profit. Producers need to critically manage crop inputs and have a relatively good assurance that any specific input actually has a high probability of having a positive effect on the crop. One method that has been proposed which can lead to a more efficient management of inputs is the use of a 'feedback' approach to input management. This is contrasted by a 'scheduled' approach, which commonly involves the scheduling of inputs based upon a calendar or days after planting. The 'feedback' approach to input management can employ crop monitoring techniques in order to ascertain the past and current status of the crop. The resultant information can then be used to make informed management decisions.
• Ozuna, S. E., Norton, E. J., & Silvertooth, J. C. (1998). Fruiting distribution patterns among three cotton varieties under irrigated conditions. 1998 proceedings Beltwide Cotton Conference, January, San Diego, volume 2, 1725-1730.
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  Abstract: A field experiment was conducted at the UA Maricopa Agricultural Center (MAC) to determine the fruiting distribution patterns of two commonly grown Upland varieties, DP 33b and DP 5415, and one American Pima variety, Pima S-7. Results indicate that cotton plants (G. hirsutum L. and G. barbadense L.) produce total yield at fruiting branches one through 18, with the majority of yield occurring at fruiting branches one through 12. Among these fruiting branches, the majority of yield is occurring at fruiting positions one and two. These results indicate that the bulk of the yield is produced early in the season and declining as the season progresses, in general with the highest yields occurring at fruiting branch one and then declining at subsequent fruiting branches.
• Smith, J. H., Silvertooth, J. C., & Norton, E. R. (1998). Comparison of two methods for the analysis of petiole nitrate nitrogen concentration in irrigated cotton. Proceedings of the 1998 beltwide cotton conferences, San Diego, CA, USA, January 5-9 1999, 651-652.
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  Abstract: A study was conducted in Arizona in 1997 with the objective of analyzing the accuracy of a recently developed portable nitrate meter (Cardy meter) to effectively measure nitrate-nitrogen (NO3-N) in irrigated cotton (Gossypium ssp.). This task was accomplished by performing a correlation and linear regression analyses on NO3-N concentrations of cotton petiole sap, as measured by the Cardy meter, against the standard procedure using dried petiole NO3-N concentrations, as measured by the ion selective electrode (ISE). Results revealed that the NO3-N concentrations of petiole sap were highly correlated with dried petiole NO3-N (pearson correlation coefficient = 0.96, P
• Unruh, B. L., & Silvertooth, J. C. (1997). Planting and irrigation termination timing effects on the yield of Upland and Pima cotton. Journal of Production Agriculture, 10(1), 74-79.
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  Abstract: There have been conflicting results reported about the effect on cotton (Gossypium spp.) lint yield of altering planting and irrigation termination (IT) timing. The objectives of this study were to identify a planting window (PW), on a heat unit (HU) basis, and IT timing, as a function of crop growth stage, for optimum yield potential of Upland (G. hirsutum L.) and American Pima (G. babadense L.) cotton. Two PWs of Upland 'Deltapine 90' (DPL 90), Pima 'S-6', and IT treatments were included in field experiments for 11 site-years. Planting windows were defined as PW1 and PW2 for plantings prior to and following 600 HU accumulated after 1 January, respectively. Two IT treatments were imposed for each planting. Irrigation termination in the desert Southwest generally results in cessation of growth (crop termination). The first IT treatment (IT1), was imposed to ensure full development of bolls set up to cutout, and the second (IT2) was after two additional irrigations. From covariate analysis, there was no evidence of interaction between PW and IT, indicating that these treatments responded the same across the different environments for both cotton species. There were, however, differences in lint yields among treatments. For DPL 90, PW1 IT2 yielded 83 and 97 lb/acre more than PW1 IT1 and PW2 IT2; and for Pima S-6, PW1 IT2 was 118 and 204 lb/acre more than PW1 IT1 and PW2 IT2, respectively. Early planting is necessary for optimum yield potential of full-season cotton varieties; with the greatest yield coming from early planting and termination after the development of a second fruiting cycle (PW1 IT2). However, if a reduction in input costs and the avoidance of late-season insect pests are important considerations then cotton should be planted early (300 to 600 HU after 1 Jan) and terminated at the end of the first fruiting cycle (approximately 600 HU past cutout) to maintain the lint yield potential of full-season maturity types of Upland and Pima cotton.
• Sanchez, C. A., & Silvertooth, J. C. (1996). Managing Saline and Sodic Soils for Producing Horticultural Crops. Horttechnology, 6(2), 99-107. doi:10.21273/horttech.6.2.99
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  Summary. About 33% of all irrigated lands worldwide are affected by varying degrees of salinity and sodicity. Soil with an electrical conductivity (EC) of the saturated extract >4 dS·m -1 is considered saline, but some horticultural crops are negatively affected if salt concentrations in the rooting zone exceed 2 dS·m -1 . Salinity effects on plant growth are generally osmotic in nature, but specific toxicities and nutritional balances are known to occur. In addition to the direct toxic effects of Na salts, Na can negatively impact soil structure. Soil with exchangeable sodium percentages (ESPs) or saturated extract sodium absorption ratios (SARs) >15 are considered sodic. Sodic soils tend to deflocculate, become impermeable to water and air, and puddle. Many horticultural crops are sensitive to the deterioration of soil physical properties associated with Na in soil and irrigation water. This review summarizes important considerations in managing saline and sodic soils for producing horticultural crops. Economically viable management practices may simply involve a minor, inexpensive modification of cultural practices under conditions of low to moderate salinity or a more costly reclamation under conditions of high Na.
• Unruh, B. L., & Silvertooth, J. C. (1996). Comparisons between an Upland and a Pima cotton cultivar: I. Growth and yield. Agronomy Journal, 88(4), 583-589.
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  Abstract: American Pima cotton (Gossypium barbadense L.) is an extra-long staple cotton produced in the southwestern USA and in other regions around the world. Pima cotton generally yields less than Upland (G. hirsutum L.), but there have not been any studies conducted to document the basis for these differences. Field trials were conducted at two south-central Arizona locations from 1990 through 1992 for the purpose of comparing growth and yield between representative cultivars of Upland and Pima cotton. The aboveground portion of Upland 'Deltapine 90' (DPL 90) and Pima 'S-6' were harvested and separated into stems, leaves (including petioles), burs (carpel walls), lint, and seeds. The bur fraction also included immature fruiting forms. Dry matter accumulation was modeled as a function of heat units (HU) accumulated after planting (HUAP). Both cultivars exhibited a linear increase of total dry matter over the duration of sampling. By the end of sampling, DPL 90 produced more total, stem, seed, lint, and reproductive (bur + seed + lint) dry matter than Pima S-6; the dry matter that accumulated in leaves, bur fraction, and vegetative structures (leaf + stem) did not differ. The reproductive/vegetative ratio (RVR) was found to be similar for both cultivars, increasing rapidly with HU accumulation. Comparisons of lint dry matter accumulation as a function of RVR and harvest index (HI) revealed that DPL 90 yields more lint than Pima S-6 due to a greater total biomass production and more efficient partitioning of dry matter into reproductive organs.
• Unruh, B. L., & Silvertooth, J. C. (1996). Comparisons between an Upland and a Pima cotton cultivar: II. Nutrient uptake and partitioning. Agronomy Journal, 88(4), 589-595.
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  Abstract: Uptake and partitioning of N, P, and K by Upland cotton (Gossypium hirsutum L.) have been studied, but no such work has included American Pima cotton (G. barbadense L.). Our objective was to describe the N, P, and K uptake and partitioning into various plant parts for two representative Upland and Pima cotton cultivars. Upland 'Deltapine 90' (DPL 90) and Pima 'S- 6' were grown at two south-central Arizona locations for 3 yr. Beginning 14 to 20 d after emergence, the aboveground portions of cotton plants were harvested and separated into stems, leaves (including petioles), burs (carpel walls), lint, and seeds. The bur fraction also included squares, flowers, immature bolls, and burs from mature bolls. Total N, P, and K analyses were conducted on each fraction (except lint). Nutrient concentration, uptake, and partitioning by cotton was modeled on a heat unit accumulation basis (HUAP). Up to about 1500 HUAP, leaves were major N sinks, leaves and the bur fraction were major P sinks, and leaves and stems were major K sinks for both cultivars. After 1500 HUAP, the bur fraction and seeds were major N and P sinks and the bur fraction was the major K sink. For DPL 90, the total N, P, and K uptake was 201, 31, and 254 kg ha-1 and for Pima S-6, it was 201, 32, and 226 kg ha-1, respectively. Nutrient requirements for producing 100 kg lint ha-1 were 15-2.3-19 kg ha-1 N-P-K for Upland cotton and 21-3.3-23 kg ha-1 for Pima cotton.
• Wrona, A. F., Guthrie, D. S., Hake, K., Kerby, T., Lege, K. E., & Silvertooth, J. C. (1996). The 1995 production year. Beltwide cotton conferences. Proc. conf. Nashville, 1996. Vol. 1, 3-6.
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  Abstract: This overview of the 1995 production season is a compilation of information provided by extension agronomists and entomologists from across the Cotton Belt. With the exception of last year, producers can be pleased with recent trends in upland cotton yields in the US. However, whereas records for yield, production and price were set in 1994, the 1995 season was disappointing. Yields for 1995 look slightly better when compared with five-year yield averages for each of the cotton producing states. In spite of an increase in acreage planted to cotton in all four regions, yields in terms of pounds of lint produced per acre decreased. Production, as total bales produced, also decreased across the belt with the exception of the Southeast where a resounding 59% increase in acreage compensated for the decreased yields also experienced in that region.
• Unruh, B. L., Silvertooth, J. C., & Hendricks, D. M. (1994). Potassium fertility status of several Sonoran desert soils. Soil Science, 158(6), 435-441.
• Silvertooth, J. C., Watson, J. E., Malcuit, J. E., & Doerge, T. A. (1992). Bromide and nitrate movement in an irrigated cotton production system. Soil Science Society of America Journal, 56(2), 548-555.
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  Abstract: A field experiment was conducted for the purpose of determining the worst-case potential for solute leaching under furrow-irrigated conditions, and to assess the spatial variability associated with solute movement. The experiment was carried out on a Mohall sandy loam soil (Typic Haplargid) within a field of upland cotton with uniformity of all management factors, including fertilizer N and irrigation water. Appreciable amounts of solute movement were measured, with a very high degree of spatial variability. The highest degree of leaching potentials was measured early in the season, when soil water depletions were the lowest and crop root development would not be extended past very shallow regions of the soil profile. The results reinforce the need to split fertilizer-N applications throughout the course of a growing season. -from Authors
• Inskeep, W. P., & Silvertooth, J. C. (1988). Inhibition of hydroxyapatite precipitation in the presence of fulvic, humic, and tannic acids. Soil Science Society of America Journal, 52(4), 941-946.
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  Abstract: The objectives of the present study were to (i) determine if soluble organic materials common in soils and natural waters influence the rate of HAP precipitation and, (ii) determine the mechanism of inhibition of organic constituents on the precipitation of HAP. To accomplish these objectives the authors studied HAP precipitation in controlled seeded crystal growth experiments in the absence and presence of humic, fulvic, tannic, and other smaller molecular weight organic acids. Study materials, methods and results are discussed.
• Inskeep, W. P., & Silvertooth, J. C. (1988). Kinetics of hydroxyapatite precipitation at pH 7.4 to 8.4. Geochimica et Cosmochimica Acta, 52(7), 1883-1893.
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  Abstract: The rate of hydroxyapatite (HAP) precipitation was studied using a reproducible seeded growth technique under pH stat conditions. Thirty different experiments were performed at initial Ca2+ and PO43- concentrations ranging from 0.37-0.86 and 0.29-1.0 mmol L-1, respectively, ionic strengths from 0.015-0.043 mol L-1, HAP seed concentrations from 7.1-28.4 m2 L-1, temperatures from 10-40°C, and pH from 7.4 to 8.4. Initial rates expressed as mole HAP L-1 s-1 were used to test several empirical rate equations and derive a rate equation based on experimentally determined reaction orders. The rate equation: R = kfsγ2γ3[Ca2+][PO43-], where R = rate of HAP precipitation (mol HAP L-1 s-1), kf = rate constant (L2 mol-1 m-2 s-1), γ2 and γ3 = divalent and trivalent ion activity coefficients, s = surface area (m2 L-1), and brackets = concentrations of Ca2+ and PO43- (mol L-1), was derived based on the reaction orders with respect to S, [Ca2+] and [PO43-]. The equation was also verified using the integral method, and the average value for the precipitation rate constant was 173 ± 11 L2 mol-1 m-2 s-1. The Arrhenius activation energy was 186 ± 15 kJ mol-1, indicative of a surface controlled precipitation mechanism. We speculate that the rate limiting steps include migration of surface Ca2+ and HPO42- into lattice vacancies, with subsequent dehydration and incorporation into the crystal lattice. © 1988.
• Silvertooth, J. C., & Westerman, R. L. (1988). Digestion of plant materials for the determination of total nitrogen to include nitrate. Agronomy Journal, 80(5), 733-736. doi:10.2134/agronj1988.00021962008000050007x
• Barreto, H. J., Minter, D. L., Silvertooth, J. C., & Westerman, R. L. (1984). Phosphorus and potassium effects on yield and nutrient uptake in arrowleaf clover. Soil Science Society of America Journal, 48(6), 1292-1296. doi:10.2136/sssaj1984.03615995004800060018x
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  Arrowleaf clover (Trifolium vesiculosum Savi 'Yuchi') is a winter annual legume that can be used to extend the grazing of warm-season perennial grasses in forage production systems. Stand establishment from overseeding often fails because of unfavorable climatic coditions and nutrient deficiencies in soils. The objectives of this research were to determine the effects of P and K fertilization on yield and nutrient uptake of arrowleaf clover and accumulation of soil P and K. Arrowleaf clover was seeded in field plots in the fall of 1978. Fertilizer treatments consisted of an incomplete factorial arrangement of multiple rates of P, K, and P plus K. The soil type was a Taloka silt loam (Mollic Albaqualfs). Yield and N, P, and K uptake in forage were determined in four consecutive years starting in 1979. Soil test indices were measured prior to seeding in 1977, in the fall of 1978, and after four annual fertilizations in 1982. Regression equations with linear, quadratic, and interaction terms were calculated to describe dependent variable response surfaces for each year and the average over years. Phosphorus fertilization increased yield each year.
• Westerman, R. L., Silvertooth, J. C., Barreto, H. J., & Minter, D. L. (1984). PHOSPHORUS AND POTASSIUM EFFECTS ON YIELD AND NUTRIENT UPTAKE IN ARROWLEAF CLOVER.. Soil Science Society of America Journal, 48(6), 1292-1206.
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  Abstract: Arrowleaf clover (Trifolium vesiculosum Savi 'Yuchi') is a winter annual legume that can be used to extend the grazing of warm-season perennial grasses in forage production systems. Stand establishment from overseeding often fails because of unfavorable climatic coditions and nutrient deficiencies in soils. The objectives of this research were to determine the effects of P and K fertilization on yield and nutrient uptake of arrowleaf clover and accumulation of soil P and K. Arrowleaf clover was seeded in field plots in the fall of 1978. Fertilizer treatments consisted of an incomplete factorial arrangement of multiple rates of P, K, and P plus K. The soil type was a Taloka silt loam (Mollic Albaqualfs). Yield and N, P, and K uptake in forage were determined in four consecutive years starting in 1979. Soil test indices were measured prior to seeding in 1977, in the fall of 1978, and after four annual fertilizations in 1982. Regression equations with linear, quadratic, and interaction terms were calculated to describe dependent variable response surfaces for each year and the average over years. Phosphorus fertilization increased yield each year.

Proceedings Publications

• Barnes, E. M., Hagler, J. R., Hunsaker, D. J., Pinter, P. J., & Silvertooth, J. C. (2004). Scheduling Cotton Irrigations Using Remotely-Sensed Basal Crop Coefficients and FAO-56. In 2004, Ottawa, Canada August 1 - 4, 2004.
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  Techniques to more accurately quantify crop evapotranspiration (ETc) are needed for determining crop water needs and appropriate irrigation scheduling. In this study, remotely sensed observations of the normalized difference vegetation index (NDVI) were used to estimate cotton basal crop coefficients (Kcb), which were then applied within the dual crop coefficient procedures of the Food and Agricultural Organization (FAO), Paper 56 (FAO-56) to calculate daily ETc. An experiment in central Arizona during 2003 compared irrigation scheduling using a remotely sensed Kcb technique (NDVI treatment) with the FAO-56 Kcb curve (FAO treatment). The FAO curve was locally developed for optimum crop conditions and standard cotton density. Final lint yield means were not significantly different between the two irrigation methods, which included sub-treatments of two levels of nitrogen and three plant densities. However, NDVI attained higher yields under low N input, whereas FAO generally had higher yields under high N. The ETc estimated using the NDVI-Kcb method was in closer agreement with measured cumulative ETc than the FAO Kcb. For high N treatments, the mean absolute differences between measured and estimated cumulative ETc during the growing season for typical, dense, and sparse populations (10, 20, and 5 plants m-2, respectively) were 4, 17, and 4 mm, respectively, for NDVI, whereas they were10, 32, and 13 mm, respectively, for FAO. Although additional research is needed for improving our remote sensing technique, it potentially offers an improvement over the FAO Kcb curve for quantifying actual ETc.

Presentations

• Silvertooth, J. C. (2023, 8 March).

  “Soil Health: Background and Fundamentals”.

  Attendance: 30

  . 8 March 2023. UA Cooperative Extension Soil Health Workshop, Phoenix, AZ.. UA Cooperative Extension Soil Health Workshop, Phoenix, AZ.: UA Cooperative Extension.
• Silvertooth, J. C. (2023, April).

  13 April 2023.  “Soil Health in Desert Crop Production Systems”.  California-Arizona Pest Control Association.  Brawley, CA.

  Attendance: 68

  . California-Arizona Pest Control Association. Brawley, CA.. Brawley, CA: California-Arizona Pest Control Association..
• Silvertooth, J. C. (2023, August).

  15 August 2023.  “Soil Fertility and Plant Nutrition Management”.  UA Cooperative Extension Pima County Master Gardener Program.  Attendance: 40

   

  . UA Cooperative Extension Pima County Master Gardener Program.. Tucson, AZ: UA Cooperative Extension Pima County Master Gardener Program..
• Silvertooth, J. C. (2023, August).

  16 August 2023.  “Soil Fertility and Plant Nutrition Management”.  UA Cooperative Extension Pima County Master Gardener Program.  Attendance: 40

  . UA Cooperative Extension Pima County Master Gardener Program.. Tucson, AZ: UA Cooperative Extension Pima County Master Gardener Program..
• Silvertooth, J. C. (2023, December).

  13 December 2023.  “Dynamics of the Western Water Outlook for 2024”.  Western Forage and Alfalfa Symposium.  Sparks, NV.  Attendance: 400

  . Western Forage and Alfalfa Symposium. Sparks, NV.. Sparks, NV: Western Forage and Alfalfa Symposium. Sparks, NV..
• Silvertooth, J. C. (2023, July).

  19 July 2023.  “Soil Health”.  UA Cooperative Extension Pima County Master Gardener Program.  Attendance: 40

  . UA Cooperative Extension Pima County Master Gardener Program.. Tucson, AZ: UA Cooperative Extension Pima County Master Gardener Program..
• Silvertooth, J. C. (2023, June).

  13 June 2023.  “Using Crop Phenology for Nutrient and Water Management”.  California-Arizona Pest Control Association.  Blythe, CA.

  Attendance: 59

  . California-Arizona Pest Control Association. Blythe, CA. Blythe, CA: California-Arizona Pest Control Association. Blythe, CA.
• Silvertooth, J. C. (2023, March).

  10 March 2023.  UA Cooperative Extension Soil Health Workshop, Tucson, AZ.  “Soil Health: Background and Fundamentals”.

  Attendance: 60

  . UA Cooperative Extension Soil Health Workshop, Tucson, AZ.. Tucson, AZ: UA Cooperative Extension.
• Silvertooth, J. C. (2023, March).

  13 March 2023.  UA Cooperative Extension Soil Health Workshop, Solomon, AZ.  “Soil Health: Background and Fundamentals”.

  Attendance: 30

  . UA Cooperative Extension Soil Health Workshop, Solomon, AZ.. Solomon, AZ: UA Cooperative Extension.
• Silvertooth, J. C. (2023, March).

  9 March 2023.  UA Cooperative Extension Soil Health Workshop, Flagstaff, AZ.  “Soil Health: Background and Fundamentals”.

  Attendance: 40

  . UA Cooperative Extension Soil Health Workshop, Flagstaff, AZ.. Flagstaff, AZ: UA Cooperative Extension.
• Silvertooth, J. C. (2023, Summer).

  11 July 2023.  “Improving Farming Practices”.  UA Water Resource Research Center Annual Conference.  Moderator for panel discussion.

  . UA Water Resource Research Center Annual Conference. Moderator for panel discussion.. Tucson, AZ: UA Water Resource Research Center Annual Conference..
• Silvertooth, J. C. (2011). Agronomic Studies in Irrigated Chile and Yuma Chile Experiment. New Mexico Chile Association Quarterly Project Update. Deming, New Mexico: New Mexico Chile Association.
• Silvertooth, J. C. (2011). Chile Agronomy Program - Nutrient and Water Management Studies. Chile Field Day. Pearce, AZ.
• Silvertooth, J. C. (2011). Evaluation of Mepiquat Chloride Management in Irrigated Cotton. 2011 Beltwide Cotton Conference. Atlanta, Georgia.
• Silvertooth, J. C. (2011). Managing Plant Nutrients and Soil Fertilizers for Cotton Production in Arizona. 2011 Southwest Agricultural Summit. Yuma, Arizona.
• Silvertooth, J. C. (2011). Optimizing Management Efficiencies in Irrigated Crops. 2011 AZCPA Desert Ag Conference. Casa Grande, AZ: AZCPA.
• Silvertooth, J. C. (2011). Soil and Plant Tissue Test Relationships for Irrigated Chile Production Systems. 2011 New Mexico Chile Conference. Las Cruces, New Mexico.

Poster Presentations

• Silvertooth, J. C. (2023, 23 February).

   “The Colorado River Water Shortage: Agricultural Perspectives”.  Attendance: 100

  . 23 February 2023. Southwest Ag Summit.. Yuma, AZ: Yuma Fresh Vegetable Association.
• Cusimano, J., Fausel, C., Silvertooth, J. C., Mclain, J. E., & Megdal, S. B. (2013, March). Impacts of short-term fallowing on soils and crop growth in the Palo Verde Irrigation District. Water Resources Research Center Annual Conference. Tucson, Arizona: UA-WRRC.
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  Poster presentation of Master's research.

Reviews

• Silvertooth, J. C. (2023.

  Compendium of Pepper Diseases and Disorders.  2023.  JCS role: Review and update section on nutrient disorders and deficiencies of peppers.  Ed. Soum Sanogo, New Mexico State University.

   

  . Las Cruces, NM.

Creative Productions

• Silvertooth, J. C. (2023.

  Farm Bureau Communications Network

   

              Talk to a Farmer Program (four live interview session with Julie Murphree)

              Conducted on 4, 11, 18, and 25 August 2023

   

  4 August 2023

   

  https://www.instagram.com/reel/CwYGFgNpNPh/?igshid=NzZhOTFlYzFmZQ==

   

  11 August 2023

   

  https://www.instagram.com/p/Cv0DBwWJ2Ny/

   

  18 August 2023

   

  https://www.instagram.com/reel/CwGFO8JL9i8/?utm_source=ig_web_copy_link&igshid=MzRlODBiNWFlZA%3D%3D&fbclid=IwAR1BNPwnI_fwghMxLkPMoz0k8iGmcGxvTtlPdnVaAf__zHrRikqK-KViEjs

   

  25 August

   

  https://www.instagram.com/reel/CwYGFgNpNPh/?igshid=NzZhOTFlYzFmZQ==

  . Talk to a Farmer Program (four live interview session with Julie Murphree). AZFB Instagram Program: Arizona Farm Bureau. https://www.instagram.com/reel/CwYGFgNpNPh/?igshid=NzZhOTFlYzFmZQ==
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  Live interviews
• Silvertooth, J. C. (2023.

  Interviews for Regional and National Media

   

  27 January 2023.  Morgan Loew, CBS Ch. 5, Phoenix, AZ.  Agricultural Impacts of the Colorado River Water Shortage.

   

  31 January 2023.  André Duchesne, French-Canadian journalist working at La Presse, a daily in Montreal, Canada.

  https://www.lapresse.ca/international/etats-unis/2023-02-01/reduction-de-la-consommation-d-eau-du-fleuve-colorado/la-californie-rechigne.php

  3 February 2023.  Stephanie Hines Wilson, Christian Science Monitor.  Agricultural Impacts of the Colorado River Water Shortage.

   

  7 March 2023.  Christopher Flavelle, NY Times.  Agricultural Impacts of the Colorado River Water Shortage.

   

  11 May 2023.  Liz Scherflius, AZPM, Agricultural Impacts of the Colorado River Water Shortage.

   

  11 July 2023.  Liz Scherflius article in “Tucson Lifestyle Magazine”:  Water Wars – Will Arizona be the Loser?

   

  https://www.tucsonlifestyle.com/local/water-wars-will-arizona-be-the-loser/article_7d4bd3ec-2007-11ee-880d-f3c54278c56d.html

   

   

  24 May 2023.  Shelby Slaughter, KOLD News, Tucson, AZ

   

  https://www.kold.com/2023/05/25/tucson-signs-deal-voluntarily-forfeit-portion-colorado-river-allotment/

   

  29 August 2023.  Christopher Conover and Zachary Ziegler, AZPM, Agriculture and water management in Arizona.  Why is alfalfa one of Arizona's biggest crops? 

  AZPM, 9/7/23 

  University of Arizona professor of agronomy and soil science Jeff Silvertooth discusses the place of farming and ranching in the state's traditional economy, and water as a variable in the current calculus. 

  . Various media outlets. Various media outlets: Various media outlets.
  More info

  Please note specific interview events for URL connections.
• Silvertooth, J. C. (2023.

  Bill Buckmaster Radio Program – I serve as the regular contributor in agriculture for this program and I provide monthly radio program interviews. KVOI AM 1030, Tucson, Arizona. https://www.buckmastershow.com/

   

  24 January 2023

  21 February 2023

  21 March 2023

  25 April 2023

  30 May 2023

  11 July 2023

  4 October 2023

  14 November 2023

  21 December 2023

   

  . Bill Buckmaster Radio Program – I serve as the regular contributor in agriculture for this program and I provide monthly radio program interviews. KVOI AM 1030, Tucson, Arizona. https://www.buckmastershow.com/. Tucson, AZ: Bill Buckmaster Radio Program. KVOI AM 1030, Tucson, Arizona. https://www.buckmastershow.com/. https://www.buckmastershow.com/

Other Teaching Materials

• Silvertooth, J. C. (2023.

  Agronomy Update for the Weekly Cotton Advisories, nine Arizona production areas covered weekly.  UA Cooperative Extension System. June – October 2021.

   

  UA Vegetable IPM Newsletter, University of Arizona Cooperative Extension Agronomic Contributor, 2023 Vol. 14:

              Water Management in Desert Agriculture, 11 January 2023, No. 1

              Soil Health – A Brief Introduction, 25 January 2023, No. 2

              Colorado River Water Shortage – Recent Proposals, 8 February 2023, No. 3

              Colorado River Water Shortage: Ag Perspectives, 22 February 2023, No. 4

              Colorado River Water Shortage: Ag Perspective Updates, 8 March 2023, No. 5

              Fertilizer Resources, 22 March 2023, No. 6

              Cantaloupe (Melon) Growth and Development, 5 April 2023, No. 7

              Nutrient and Water Management in Irrigated Cantaloupes, 19 April 2023, No. 8

              Basic Root System Development, 3 May 2023, No. 9

              Irrigation Efficiency and Crop Water Use, 16 May 2023, No. 10

              International Fertilizer Price Fluctuations, 31 May 2023, No. 11

  Crop Growth, Development, Nutrient, and Water Demand for Irrigated Chile (Capsicum annuum), 14 June 2023, No. 12

  Art and science of crop production.  28 June 2023, No. 13

  Chile crop nitrogen and water demand.  12 July, No. 14

  Soil formation, 26 July 2023, No. 15

  Fluctuations in international fertilizer prices.  9 August 2023, No. 16

  Colorado River Water & Arizona Agriculture.  23 August 2023, No. 17

  Soil health: Soil physical properties.  6 September 2023, No. 18

  Management proposals for Colorado River Water.  20 September 2023, No. 19

  Vegetable crop root systems.  4 October 2023, No. 20

  Plant-available water.  18 October 2023.  No. 21

  Merits of Alfalfa Production in the Desert Southwest. 1 November 2023.  No. 22

  Crop water management basics.  15 November 2023.  No. 23

  Soil health: soil cation exchange capacity.  28 November 2023, No. 24

  Vegetable crop production capacity in the U.S.  12 December 2023, No. 25 

  . UA Cooperative Extension Vegetable Intergrated Pest Management (IPM) Newsletter.
  More info

  I provide the agronomic input section for each of our UA Vegetable IPM Newsletters, which are published 2X each month.  

Others

• Cusimano, J., Megdal, S. B., Mclain, J. E., Silvertooth, J. C., Cusimano, J., Megdal, S. B., Mclain, J. E., & Silvertooth, J. C. (2014, Winter). Fallowing effects on soil quality in the Palo Verde Irrigation District. Arizona Water Resource (WRRC Quarterly Newsletter). https://wrrc.arizona.edu/sites/wrrc.arizona.edu/files/AWR%20Winter%202014%2001-07-14.pdf
  More info

  The newsletter can be found at the above URL. My role in this publication was to supervise the associated laboratory research associated with soil microbiology, and to strongly aid in editing of the final article.
• Silvertooth, J. C., & Pater, S. E. (2013, January). Cooperative Extension - Historic Milestones..
  More info

  Backyards and Beyond. Vol. 7 Number 1. Arizona Cooperative Extension. 2 pp.
• Silvertooth, J., & Norton, E. (2011, Fall). Management of Fertilizer Nitrogen in Arizona Cotton Production. Univ. of Arizona Cooperative Extension Bulletin 1243.