Jeffrey C. Silvertooth. Professor and Extension Agonomist, Department of Plant Sciences. Ph.D., Oklahoma State University. Pursuing greater efficiency of agronomic inputs into cotton production systems of Arizona.

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Jeffrey C. Silvertooth. Professor and Extension Agronomist, Department of Plant Sciences. Ph.D., Oklahoma State University. (75% Extension; 25% Research)

Office: Forbes, #214 (621-7616)

Laboratory: Forbes, #126 and #114D (621-8910)

Mobile Telephone: 603-0191

e-mail: silver@ag.arizona.edu

• Arizona Cotton Information Site: http://ag.arizona.edu/cotton

Pursuing greater efficiency of agronomic inputs into cotton production systems of Arizona.

As the Extension Agronomist - Cotton for the University of Arizona, I conduct an applied research program which is oriented towards agronomic aspects of cotton (Gossypium spp.) production in the desert Southwest and complements an Extension education program. The entire research program that I direct could be divided into seven basic categories including: (1) nutrient management/plant nutrition; (2) plant growth and development (plant phenology); (3) crop management; (4) plant growth regulators; (5) crop simulation models; (6) seed treatment evaluation; and (7) variety testing. These research projects involve field experiments at numerous locations across the cotton producing areas of Arizona and both Upland (G. hirsutum L.) and American Pima (G. barbadense L.) cotton. Extensive laboratory activities are also conducted to complement and support the field research program.

A major area of focus in my research program is that of soil-plant relationships regarding several important nutrients essential to cotton. Nitrogen (N) management experiments are being conducted with the principal objective of refining and demonstrating the use of best management practices (BMP's) associated with managing N in irrigated cotton production systems. A group of experiments are also being conducted to characterize the leaching potential of soil solutes such as NO3--N. These experiments utilize bromide (Br-), a biologically conserved anionic solute, as an analogue of NO3- to assess the worst-case leaching potential of such solutes under irrigated conditions. In addition, experiments are being conducted using 15N, a naturally occurring stable isotope of N, as an enriched label on fertilizer N to determine fertilizer N efficiencies, uptake and recovery, and explicit measurements of fertilizer derived N movement within the soil-plant system.

Several research projects have also been directed towards identifying conditions which may lead to deficiencies of phosphorus (P), potassium (K), and zinc (Zn). In this regard, experiments have been conducted which characterize the soil-chemical, and physical environment concerning these nutrients, and the plant response associated with additions of fertilizer sources of these nutrients. The nutrient uptake patterns for N, P, K, and Zn are also being studied and described for both Upland and Pima cotton.

Another major focus in my research program is directed towards the development of cotton production management strategies that optimize the soil-plant system agronomically and economically, with full consideration of the short- and long-term impact of inputs environmentally. Cotton production in the desert Southwest has traditionally been oriented towards long, full-season production, with a goal of attaining the absolute maximum agronomic yields possible. An alternate approach is that of pursuing the maximum "economic" yields. With the perennial, indeterminate nature of the cotton plant, this requires the identification of the "point of diminishing return" with regard to the inputs necessary to sustain full-season production. A series of experiments are being conducted which are part of an interdisciplinary research project. The goal is to significantly 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.

Silvertooth, J.C., K.L. Edmiston, W.H. McCarty, and D.R. Krieg. 1999. Production practices. In Cotton (a monograph), C.W. Smith and J.T. Cothren, Eds. John Wiley & Sons. New York, NY. p. 451-488.

Steger, A., J.C. Silvertooth, and P.W. Brown. 1998. Upland cotton growth and yield response timing the initial post-plant irrigation. Agron. J. 90: 455-461.

Norton, E.R. and J.C. Silvertooth. 1998. Field testing and validation of modeled soil solute movement in an irrigated cotton system. Agron. J. 90:623-630.

Unruh, B.L. and J.C. Silvertooth. 1997. Date of planting and irrigation termination effects on yield of Upland and Pima cotton. J. Prod. Agric. 10(1):74-79.

Sanchez, C.A. and J.C. Silvertooth. 1996. Managing saline and sodic soils for producing horticultural crops. HortTech 6(2):99-107.

Unruh, B.L. and J.C. Silvertooth. 1996. Comparisons between an Upland and a Pima cotton cultivar: II. Nutrient uptake and partitioning. Agron. J. 88:589-595.

Unruh, B.L. and J.C. Silvertooth. 1996. Comparisons between an Upland and a Pima cotton cultivar: I. Growth and yield. Agron. J. 88:583-589.

Unruh, B.L., J.C. Silvertooth, and D.M. Hendricks. 1994. Potassium fertility status of several Sonoran desert soils. Soil Sci. 158(6):435-441.

Silvertooth, J.C., J.E. Watson, J.E. Malcuit, and T.A. Doerge. 1991. Solute movement in an irrigated cotton production system. Soil Sci. Sco. Am. J. 56:548-555.

Silvertooth, J.C. 1991. Fertilizer use in cotton production worldwide. In W. Wichmann (ed.) International Fertilizer Use Review. International Fertilizer Industry Association. Paris, France. p. 457-471.

Watson, T.F. and J.C. Silvertooth. 1992. Seasonal dynamics of sweetpotato whitefly, Southwest Entomologist Journal 17(2):149-167.

Unruh, B.L., J.C. Silvertooth, and D.M. Hendricks. 1994. Potassium fertility status of several sonoran desert soils. Soil Sci. 158(6):435-441.

Unruh, B.L. and J.C. Silvertooth. 1996. Nitrogen, phosphorus, and potassium uptake by Upland and Pima cotton. Agron. J.