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The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers. / A drip irrigation trial was conducted at Eloy, Arizona to investigate optimal irrigation levels for cotton. Five irrigation levels (23.6, 26.7, 29.9, 32.8 and 33.8 acre inches) were applied to DPL 41, DPL 90 and DPL 774. The varieties were planted at 5, 10, and 20 pounds/acre. There were no statistical differences in yield in the 3 wetter irrigation treatments. Both of the drier water levels produced significantly lower yields. Significant differences were also detected in the response of the varieties and populations.

The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers.

The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers. / Nitrogen at five rates and water at three levels (0.6, 1.0, and 1.3 CU) were studied in a buried drip irrigation system on a Casa Grande sandy loam soil at the Maricopa Agricultural Center in 1985. Yield was increased by N at 50 lbs/Ac on the 1.0 and 1.3 CU water levels but not at the 0.6 CU water treatment. Yields were higher with increasing water application, 28.6" < 40.4" < 48.9". Soil nitrate-N was lower in 1985 than 1984 resulting in a greater fruiting and yield response to applied N fertilizer.

The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers. / Fertilizer nitrogen rates and the addition of phosphorus, potassium and zinc were studied in a drip irrigated field at Eloy. Response to nitrogen was found with the optimum rate being about 170 lbs/acre although higher rates tended to increase yields. Significant response to P and K were not found, but there appeared to be a response to zinc. Yields were below desired levels because of problems with obtaining a good stand and infestations of cotton rust and root rot.

The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers. / A modified, low- pressure linear move irrigation system was used to irrigate cotton at the Marana Agricultural Center, University of Arizona in 1985. Irrigations were scheduled using the Crop Water Stress Index (CWSI) for timing and a neutron probe to determine soil moisture deficits. Irrigations were applied when the CWSI reached 0.1 resulting in minimal seasonal water stress. Yields ranged from 3.14 bales /acre to 2.73 bales/acre from 2 acre plots. Total applied water ranged from 31.3 inches to 32.3. Total seasonal rainfall was 2.90 inches.

The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers. / Planting pattern 2x1 skip row cotton outyielded variable row 32"x44" per gross field acre under drip irrigation with saline water. Skip row planting in deep water areas appears to be a feasible selection with high water cost, reduced tubing requirement, lowered land rentals and increased yield response.

The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers. / Both trickle and level-basin irrigation methods, when properly managed and operated, achieved high cotton yields and water use efficiencies on a low water holding capacity soil in 1985. A maximum lint yield of 1906 kg/ha (3.8 bales/ac) was achieved for the DPL-90 variety with a single trickle irrigation line per every two rows irrigated daily on the narrow row spacing; however, the new DPL-775 was best overall. The single trickle line per every two rows irrigated daily averaged 15% more lint cotton than the level-basin, every furrow irrigated weekly for both row spacings. The narrow-row spacing (30 inch between rows) outyielded the conventional spacing (40 inch between rows) by 15%, partly because of a higher plant populations. Daily trickle irrigations averaged about 10% more yield than the twice weekly trickle irrigations, and the weekly level-basin irrigations averaged over 20% increase in yield over the biweekly (every two weeks) level-basin irrigations. Light-frequent irrigations can be advantageous for nonhomogenous soils in the semiarid Southwestern United States.

The 1985 and 1986 Cotton Reports have the same publication and P-Series numbers. / Deltapine 90 was grown under daily trickle, and weekly and bimonthly level-basin irrigation treatments. The cotton in each treatment received equal amounts of irrigation water over the course of the growing season. The daily irrigated plants maintained more constant leaf water potential (WP) and net photosynthesis (Pn) than the level-basin irrigated plants. The level-basin irrigated plants experienced water stress-induced reductions in WP and Pn prior to irrigation.