ABSTRACT
Development of cotton harvesting equipment which can spindle harvest 30- to 32-in rows has led to a renewed interest in narrow-row cotton production systems for the Mississippi Delta. Three studies were initiated at Stoneville, MS in 1989 to determine the feasibility of narrow-row cotton production compared to conventional 38- to 40-in systems. Factors evaluated in these studies consisted of row spacing, planting patterns, planting dates, nitrogen (N) management, plant growth regulators and varieties. Only the evaluation of N management and plant growth regulator applications will be discussed in this report. The objectives of this specific study included 1) determination of optimum N management by evaluation of N rates and application timing; 2) field evaluations of PIX (mepiquat chloride) plant growth regulator need and utilization; and 3) evaluation of plant characteristics and yield by GOSSYM/COMAX and COTMAP. Urea-ammonium nitrate (32% N) solution was applied either 100% preplant (PP) or 50% PP and 50% as a delayed sidedress application at early-bloom at rates of 90, 120, and 150 lb N/A. PIX application consisted of low rates and multiple applications (LRMA) as needed and no application. In both 1989 and 1990, all plots had to be replanted before sufficient stands were established. After two years of research, the 30-in row production system produced significantly higher yields in both 1989 (112 lb lint/A) and 1990 (98 lb lint/A) compared to the 40-in row production system when means were determined over rate, application system, and PIX applications. In 1989, 150 lb N/A decreased yields in both 30-in and 40-in row spacings, with the 100% PP application system producing higher yields than the split application system. In 1990, there was no significant yield response to N rates above 90 lb N/A and no significant difference between the N application systems. The 2-year average showed no response to increased N for 30-in rows, however, yields tended to decrease as N rate increased above 90 lb N/A. The 2-year average also showed no significant difference between the N application systems. It should be noted that in 1990, the PP applications were delayed until uniform stands were established. PIX application resulted in significant yield increase in 1989 but not in 1990. Further evaluations are underway to define the most acceptable and feasible 30-in row production system for the Mississippi Delta.
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