A row spacing study was conducted at the Safford Agricultural Center from 1989 to 1991, evaluating the effects of 40 inch, 36 inch, 36-30 inch and 30 inch row spacing on Pima and upland cotton. The results of the study are not clear cut in favor of narrow or wide row cotton. Trends make it appear that narrow rows are more favorable for upland than Pima cotton varieties. Insufficient data is available at this point to make a firm recommendation.

Each planting season in the Safford valley there are fields that suffer stand reduction from adverse weather conditions. This study addresses some of the options and the economical effects from exercising these options on a field at the Safford Agricultural Center. References are made to work in California that have quantified the yield effect of stand reduction and chilling damage to cotton seedlings. This study shows that patience may pay better than rushing into the field to replant or rewater.

Four field experiments were carried out in several representative cotton producing areas of Arizona to evaluate the effectiveness of a number of defoliation treatments on Pima cotton. Somewhat variable but generally hot and dry conditions were encountered among the experimental locations in 1991 for treatment comparisons. It appears that consistencies in the effectiveness of several treatments for Pima defoliation offer a basis for further refinement of recommendations across the state.

A preliminary study of several defoliants and /or combinations was made on the Safford Agricultural Center. Even though conditions were less than ideal because of cool temperatures, acceptable defoliation occurred under several of the treatments. In fact, three of the treatments performed better than sodium chlorate, which is the predominant defoliant used in the area.

A field study was conducted at the Maricopa Agricultural Center to determine the influence of plant water status at the time of defoliation on the effectiveness of defoliants and yield of short-season cotton. Irrigation termination dates of 14 and 26 August and 10 September were used to achieve different levels of plant water stress at the time defoliants were applied (19 September). Irrigation termination dates had no effect on seedcotton yield for cotton defoliated in September. As the period between the termination irrigation and the date of chemical defoliation was increased the effectiveness of defoliants was increased. CWSI and plant water potential measurements indicated that the irrigation termination dates resulted in large differences in plant water stress at defoliation time. There was a significant increase in the defoliation percentage as CWSI values increased (from 0.32 to 0.96) and water potential decreased (from -1.5 to -3.5 MPa). Short- season cotton (163 days) produced 4,396 lbs. seedcotton /A as compared to 5,299 lbs./A for a full-season crop (212 days).

Field studies have been conducted over a four year period at the Maricopa Agricultural Center to determine the influence of nitrogen (N) fertility level on the effectiveness of chemical defoliants for short- season cotton production. Excessive N resulted in dense foliage and cotton that was difficult to defoliate. When plants were deficient in N from mid-season to termination, defoliants were very effective, but lint yields were reduced. The effectiveness of defoliants decreased as the petiole NO₃-N content increased. The optimum fertility program for short-season cotton is one that provides sufficient N during the season to produce maximum lint yields, but allows the crop to become deficient in N at the end of the season, prior to chemical defoliation.

Arizona Cooperative Extension generates and distributes weather -based Planting Date and Cotton Development Advisories for 10 cotton production areas (Marana, Litchfield Pk, Pinal Co., Parker, Safford, Yuma Valley, Dateland and Aguila). Planting Date Advisories are distributed from mid - February through the end of April and stress 1) planting all (particularly full season varieties) cotton varieties according to heat unit accumulations rather than calendar date and 2) the importance of soil temperature to good germination. Cotton Development Advisories are distributed from early May through mid -September and provide updates on crop developmen4 insects, weather and agronomy to growers. The Cotton Advisory Program will continue in 1993 and growers may obtain the advisories by mail (far only in Yuma County only) from the local county extension office or by computer from the AZMET computer bulletin board.

Six field experiments were conducted at three locations in 1992 in Arizona to evaluate the response of Upland and Pima cotton to dates of planting and dates of irrigation termination. Planting dates ranged from as early as 11 March in the Yuma Valley (150 ft. elevation) to 30 April at Marana (2,000 ft. elevation). Dates of irrigation termination ranged from 15 July in the Yuma Valley to 18 September at Maricopa. Planting date was commonly a significant effect in these experiments, particularly with Pima cotton. Irrigation termination results over three locations and four seasons show increases of approximately 60 to 120 lbs. lint /acre by extending later irrigations.

A crop monitoring program has been developed specifically for varieties and environmental conditions unique to Arizona. The monitoring program involves early season development guidelines, growth stage guidelines, and in- season evaluation of crop condition (vegetative /reproductive balance and fruit retention), by use of simple measurements such as height:node ratios (HNR), nodes above the top white bloom (NAWB) counts, and fruit retention estimates from plant mapping. The preliminary work necessary in terms of providing accurate and precise descriptions of the various crop development parameters has been provided through a detailed cotton phenology project conducted over many site years of experimental work. The resultant baselines describing crop development /monitoring parameters have been scaled as a function heat unit (HU, 86/55° F thresholds) accumulations. Application of these baselines have been developed through another facet of the research program to provide a basis for a feedback approach to crop management for inputs such as water, nitrogen (N), plant growth regulators, etc.. The crop monitoring program serves as a fundamental component to an active extension education program being delivered on a statewide basis to all cotton producing areas in Arizona.

A row spacing study was conducted on both long and short staple cotton on the Safford Agricultural Center. The results of this study showed that yields increased from the narrower spaced rows (36 -30 inch and 30 inch spacings) to the wider spaced rows (36 inch and 40 inch spacings). This is the same trend as reported previously with long staple cotton but differs from that previously reported for short staple cotton. Yields of 1.67 and 25 bales per acre for long and short staple cotton were reported.