Two field experiments were conducted in Arizona in 1990 at two locations ( Maricopa and Safford). The purposes of the experiments were to validate and refine nitrogen (N) fertilization recommendations for both Upland and Pima cotton. The experiments each utilized N management tools such as pre - season soil tests for NO₃⁻-N, in-season plant tissue testing (petioles) for N fertilirystatus, and crop monitoring to ascertain crop fruiting patterns and crop N needs. Results at both locations revealed a strong relationship between the crop fruit retention levels and N needs for the crop. This pattern was further reflected in final yield analysis in response to the N fertilization regimes used. At Maricopa, fruit retention levels were low, petiole NO₃⁻-N concentrations relatively high, and yield responses to higher and later applications of fertilizerN were negative. At Safford, fruit retention levels were higher, petiole concentrations of NO₃⁻-N reflected strong crop demand, and a positive response to rates of fertilizer N up to 170 lbs. N/acre was measured.

Over a three year study, two reduced tillage systems used significantly less energy than conventional tillage. The Sundance system averaged 46% of the energy used by the conventional system, and the Uprooter-Shredder-Mulcher (USM) averaged 65% of the energy used by the conventional system. These energy savings translate directly into cost savings of about the same proportions. Additionally, the Sundance and USM systems can plow down and prepare the next seedbed in about one-half the time that conventional tillage requires. In three years of testing we have not detected any significant differences in soil compaction, and we have not measured any yield reductions from these reduced tillage systems.

Two field experiments were established in Arizona in 1990 to evaluate the effects of banded phosphorus (P) fertilizer on cotton. Experiments involved both Upland (Gossvpium ltirsutum, L.) and American Pima (Q. barbadense L.). Banded applications of P fertilizerwere made with placement of the concentrated band of fertilizer 6 in. below and 3-6 in. to the side of the zone of seed placement. The P₂O₅ was supplied from 10-34-0. Rates of applied P ranged from 0 to 160 lb P₂O₅ /acre. In one experiment, treatments consisting of 5 to 10 lbs. Zn/acre were included in all possible combinations with the P₂O₅ treatments. In all cases, treatments in the field were arranged in a randomized complete block design with four replications. Plant measurements for plant height, flower numbers per unit area, number of mainstem nodes, and nodes to the first fruiting branch were initiated by the fifth true leaf stage to evaluate plant response in terms of growth and development. Plant tissue samples were also taken at several stages of growth from each experiment throughout the growing season. Tissue samples consisted of petioles from the uppermost fully - developed leaves. Petioles were analyzed for extractable PO₄-P. Lint yield measurements also were taken. No statistically significant differences (P ≤ 0.05) were found among any treatments for any of the plant growth parameters. The same was true with regard to petiole PO₄-P levels measured. No significant differences were detected among Upland or Pima cotton lint yields in response to the applications of P fertilizers.

The results of field studies with N rates from 0 to 336 kg/ha, in combination with two growth regulators, ethephon (Prep® ɑ-chloroethyl phosphonic acid, Rhone-Poulenc Ag Co., Research Triangle Parr NC) and thidiazuron (Dropp® N- phenyl -N' -1,2,3 -thiadiazol -5ylurea, Nor-Am Ag Prod. Inc., Naperville, IL). Results showed that sidedress applications of N (ammonium nitrate) to cotton did not influence the defoliation effects of ethephon and thidiazuron, or reduce number of immature green bolls at harvest. Under short-season conditions, sidedress N applications did not effect yields. Ethephon and thidiazuron at the rates tested did not affect cotton lint yields. Thidiazuron alone or in combination with ethephon resulted in high percentages of cotton defoliation.

Two field experiments were conducted in Arizona in 1991 at two locations (Maricopa and Safford). The purposes of the experiments were to validate and refine nitrogen (N) fertilization recommendations for both Upland and Pima cotton. The experiments each utilized N management tools such as pre-season soil tests for NO₃⁻-N, in- season plant tissue testing (petioles) for N fertility status, and crop monitoring to ascertain crop fruiting patterns and crop N needs. Results at both locations revealed a strong relationship between the crop fruit retention levels and N needs for the crop. This pattern was further reflected in final yield analysis as a response to the N fertilization regimes used.

A single field experiment was conducted near Gila Bend, Arizona in 1991 to evaluate the effects of both soil and foliar applied potassium (K) fertilizersto Upland (Gossvpium hirsutum L.) cotton to a soil testing 315 ppm K (high). Soil applied K fertilizer at rates of 0, 75,150, and 225 lbs. K₂O/acre as K₂SO₄ were broadcast and preplant incorporated before listing. Foliar applications were made in all combinations with the various soil applied K treatments and consisted of four applications of 4.6 lbs. K₂O /acre as KNO₃ (10 lbs. KNO₃ /acre) over the first fruiting cycle, by a ground applicator with approximately 25 gallons per acre as carrier. No differences among treatments were detected by any plant growth measurement taken, plant tissue analyses, lint yield or lint quality determinations which were made over this experiment. Conclusions (preliminary) based upon these results indicate that K fertilization was not warranted under the conditions characterized in this single field experiment.

Integrated aquaculture utilizing pre- irrigation water will hypothetically increase the levels of dissolved nitrogen products in the resulting effluent. Research was performed to assess the levels of additional nutrients added. The results suggest however, that integrated aquaculture may reduce the amount of nitrogen as nitrate applied to the fields.

Potassium (K) fertility requirements for cotton ( Gossypium spp) have been a matter of concern due to increasing interest and emphasis on fiber quality and numerous reports of K deficiencies in various cotton producing regions. To address this matter appropriately, a thorough understanding of the chemical, physical, and mineralogical composition of the soils in question is in order. Soil samples were collected from ten sites across southern Arizona that are representative of the common agricultural soils of the region. At all locations soils were sampled to a depth of 120 cm in 30 cm increments. All soils were characterized with respect to chemical composition by the following parameters: exchangeable K, total K, cation exchange capacity and particle size analysis. With the exception of one soil (a soil not commonly employed in cotton production), none of the chemically characterized soils contained less than 150 mg K kg⁻¹ of extractable K in the surface 90 cm of soil. All of the soils contained K- bearing mica and none of the soils contained any K- fixing vermiculite. From the initial chemical and mineralogical information, K fertilization is not likely for similar situations in Arizona. Further research is under way to quantify the K-fixing ability of each soil in this survey and additional field studies are also being conducted to evaluate K fertilization in both Upland (G. hirsutum L.) and Pima (G. barbadense L.) cotton.

In a mail survey, we asked Arizona cotton growers which characteristics of a tillage system are important to them. Burial of crop residue, low cost, easy maintenance, reliability, low field work time, and breaking insect life cycles were all rated as important characteristics. Dust control was rated as not important. In rating their perceptions of conventional and alternative tillage systems, cotton farmers indicated that they were not completely satisfied with any of the currently available tillage alternatives.

Due to a limited information describing the response of cotton (Gossvpium spp.) in Arizona to K fertilization, three studies were conducted in 1992 with the objective of evaluating the response of cotton crop growth and lint yield to soil and/or foliar applications of K fertilizer. The locations of the trials included the Safford Agriculture Center (Pima clay loam), Maricopa Agriculture Center (Casa Grande sandy loam), and a site located near Coolidge, AZ on a Mohall sandy loam soil. All irrigation, pest management, and fertilization inputs (other than K) were provided on an as- needed basis throughout the season. Routine plant measurements and plant mapping analyses were carried out at each location on regular intervals throughout the season. At the Safford location both Upland (G. hirsutum L., var DPL 90) and Pima (G. barbadense L., var S-6) cotton were planted with treatments including soil and foliar K applications imposed in a factorial arrangement. All soil K applications were broadcast and preplant incorporated using K₂SO₄ as the K source at rates of 0, 200, and 400 lbs. K₂O/acre. Four 4.6 lbs K₂O /acre foliar applications of KNO₃ were applied at 1626, 2016, 2326, and 2510 heat units after planting (HUAP). The trial at the Maricopa Agriculture Center included four foliar K applications over the growing season applied to Pima cotton (S-6) at 2427, 2762, 3200, and 3515 HUAP. The six foliar treatments included rates which ranged from 0 to 37 lbs. K₂O /acre using KNO₃ as the K source. Treatments were arranged over the experimental area in a randomized complete block design with five replications. At Coolidge all K treatments were band-applied to the soil at a depth of 8 in. using two shanks per row, preplant. The treatments were 0, 218, 436, and 654 lbs. K₂O /acre using K₂SO₄ as the fertilizer source. Upland cotton (STV KC311) was planted and treatments were arranged in a randomized complete block design with four replications. Results from all three trials indicated no differences among any of the treatments (including soil verses foliar and unfertilized treatments). All of the plant measurements taken for all the locations reveal crop growth resulting in excellent fruit retention without vegetative growth (i.e. height-to-node ratios within the long -term 95% confidence intervals for both Upland and Pima cotton. This indicates ample nutrient demand so that if available soil K is inadequate to meet crop needs, deficiency symptoms and reduced yields should occur. No visual deficiency symptoms were detected for any treatment in the experiments (all locations). All plots experienced vigorous and wellbalanced growth and development throughout the growing season. The results of these K fertility experiments supports current University of Arizona recommendations that unless exchangeable K is less than 150 ppm, crop response is not likely, although an exact critical level for exchangeable K is still lacking.