Jeffrey C Silvertooth
- Associate Dean, Cooperative Extension / Economic Development
- Director, Cooperative Extension- Services
- Professor, Soil/Water and Environmental Science
- Professor, Plant Science
- Associate Director, Experiment Station
- Professor, Arid Lands Resources Sciences - GIDP
- Professor, Global Change - GIDP
- Ph.D. Soil Science (Soil Fertility)
- Oklahoma State University, Stillwater, Oklahoma, United States
- Methodology of total nitrogen determination in plant materials and the distribution of fertilizer nitrogen-15 in winter wheat
- M.S. Agronomy (Soil Fertility)
- Oklahoma State University, Stillwater, Oklahoma, United States
- Effects of iron fertilizers on soybeans
- B.S. Agriculture (Agronomy)
- Kansas State University, Manhattan, Kansas, United States
The research program has been directed towards the development of crop production management strategies (primarily irrigated cotton, chiles, and cantaloupes) 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.
Crop Science+ProductionPLS 306 (Fall 2016)
Independent StudyPLS 599 (Fall 2016)
- 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.More infoAbstract: 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.More infoAbstract: 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.
- 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.More infoAbstract: 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.
- 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.More infoAbstract: 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.
- 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.More infoAbstract: 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.More infoAbstract: 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.More infoAbstract: 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.More infoAbstract: 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).
- 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.More infoAbstract: 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.More infoAbstract: 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-.More infoAbstract: 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.More infoAbstract: 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.More infoAbstract: 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.More infoAbstract: 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.
- 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.More infoAbstract: 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.More infoAbstract: 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.More infoAbstract: 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.More infoAbstract: 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.More infoAbstract: 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.More infoAbstract: 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.
- 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.More infoAbstract: 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.
- 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.
- Silvertooth, J., & Norton, E. (2011, Fall). Management of Fertilizer Nitrogen in Arizona Cotton Production. Univ. of Arizona Cooperative Extension Bulletin 1243.