GROWTH, FLOWERING, BOLL SET, AND YIELD OF DRIP IRRIGATED COTTON IN ARIZONA.

Abstract

Studies were conducted on commercial farms in 1982 and 1983 to study the effects of above surface drip irrigation, below surface drip irrigation, and furrow irrigation on flowering, boll set, yield, and growth of cotton (Gossypium hirsutum L.). Two varieties were used in 1982, 'Deltapine 62' and 'Deltapine 90', using both above and below ground drip irrigation and Deltapine 90 was grown under furrow irrigation. In 1983 the study was conducted at a different location with above ground drip irrigation and furrow irrigation using the cotton variety 'Deltapine 41'. The irrigation water was monitored to deliver 100% of consumptive use (CU), 85% of CU, 70% of CU, 100% of CU every other day and CU which was the grower's estimate of consumptive use. All open flowers were tagged using Kwik-Lok labels dated with the day the flower opened. Tagging of flowers started from first open flower and continued for 17 weeks in 1982 and 15 weeks in 1983. Plants were sampled twice in 1982 and three times in 1983 for LAI and partitioning studies. All open bolls were harvested on a weekly basis for a total of 12 harvests. In the 1982 experiments no statistical analyses were made because the five treatments were grown in different fields and could not be randomized together. A general comparison showed that Treatment 1, Deltapine 62 above ground drip system produced the highest number of flowers but it had the lowest percent of boll set. Treatment 5, Deltapine 90, furrow system, produced the lowest number of flowers but it had the highest percent of boll set. Treatment 3, Deltapine 62 below ground drip system, had the highest boll set and Treatment 5 retained the least number of bolls. Treatment 2, Deltapine 90 above ground dry system, had the highest seed cotton yield and Treatment 5 had the lowest yield. In the 1983 experiment, there were no significant differences in flowering, boll set, or yield among the five irrigated treatments. The furrow treatment could not be compared statistically with validity with the drip treatment because it was grown in a different field but a general comparison showed that it produced the lowest number of flowers and seed cotton yield although it had the highest percent of boll set.