The importance of residual soil nitrogen (N) in the production of upland cotton in Central Arizona has not been adequately studied. A subsurface drip irrigation experiment was conducted at the Maricopa Agricultural Center to examine the effect of residual soil nitrate content on lint yields of upland cotton, and to evaluate the validity of current cotton petiole nitrate interpretations under high yielding conditions. Different levels of water and N fertilizers applied to the plot area in previous years had resulted in a range of residual NO₃-N content ranging from 36 to 166 lbs /acre. Lint yields increased from 2.8 to 4.3 bales /acre as residual soil N increased from 5.7 to 27.7 ppm NO₃-N although the correlation between yield and soil N was relatively low. This was thought to be due to difficulty in obtaining soil samples that accurately reflect the true plant availability of N in soils irrigated with drip systems. The interpretation of cotton petiole data under high yielding conditions (> 4 bales/acre) proved to be essentially the same as that currently recommended for conventional furrow irrigated cotton.

Seedling emergence, plant establishment, plant height, and seed cotton yield for cotton grown with liquid sewage sludge were similar to the seedling emergence, plant establishment, plant height, and seed cotton yield for cotton grown with recommended inorganic fertilizer. High applications of liquid sewage sludge decreased water penetration in Pima clay loam soil.

Data on the potential salts and organics leaching under cotton fertilized with municipal sewage sludge is necessary to delineate best management practices when cotton is fertilized in this manner.

No description available.

The use of nitrification inhibitors delays the conversion of ammonium fertilizers to the nitrate form and has the potential to increase nitrogen use efficiency in irrigated agriculture. Two field experiments were conducted at the Maricopa Agricultural Center in 1986 to evaluate the effect of two nitrification inhibitors (N-Serve and an experimental compound, ACP) on the growth, yield, nitrogen uptake, and fertilizer use efficiency obtained by growing cotton using buried-drip and furrow irrigation. ¹⁵N labeled ammonium sulfate was applied with and without nitrification inhibitors at the beginning of the season. Whole plant samples were taken at the end of the season to determine N uptake efficiency. No significant differences in growth, lint yield or N uptake efficiency were detected due to the application of either inhibitor. The conditions where nitrification inhibitors might improve nitrogen use efficiency in furrow irrigated cotton production are discussed.

In 1987, seed samples from three cotton fields in Avra Valley, Arizona, grown with liquid sewage sludge and inorganic nitrogen fertilizer, were analyzed for five heavy metals. Concentrations of cadmium, copper, lead, nickel, and zinc were similar in cotton seeds fertilized with either sewage sludge or inorganic nitrogen fertilizer. The levels of all five metals were well below the allowable EPA limits.

Plant growth products manufactured by BioHumaNetics, Inc. (BHN) were evaluated at the Maricopa Agricultural Center for the third consecutive year in the same field. Treatments included: 1) no fertilizers added; 2) standard fertilization used on cotton at the farm; and 3) a treatment schedule prescribed by BHN. Yields in 1987 were significantly different; the BHN treatment produced the highest yield, and the unfertilized treatment produced the lowest yield. Yields from all three treatments were substantially lower than corresponding 1986 yields.

Three field experiments were conducted in Avra Valley, Arizona, in 1986, to compare the lint quality of upland cotton fertilized with liquid sewage sludge with the lint quality of cotton fertilized with commercial inorganic fertilizer. Most lint quality components were similar for cotton fertilized with sewage sludge or inorganic nitrogen. Fertilization of cotton with sewage sludge tended to increase lint yield and decrease lint quality. Fertilization of cotton with sewage sludge increased vegetative growth and delayed lint maturity.

A field experiment was conducted in 1987 in Avra Valley, Arizona, to compare the plant growth and cotton lint yield from upland cotton fertilized with liquid sewage sludge with the plant growth and cotton lint yield from cotton fertilized with commercial inorganic fertilizer. Plant growth and cotton lint yields were similar when cotton was fertilized with liquid sewage sludge or inorganic fertilizers.

A preplant application of zinc was made to a short staple cotton field where the soil analysis had shown a zinc concentration of 0.64 ppm. No significant yield response was measured.