NARROW-ROW COTTON PRODUCTION IN THE MISSISSIPPI DELTA YIELD RESPONSE TO NITROGEN MANAGEMENT

M.Wayne Ebelhar, Randal A. Welch and Gordon R. Tupper

ABSTRACT

With the development of cotton harvesting equipment which can spindle harvest combinations of 30- or 32-in rows with various planting patterns, a renewed interest has occurred in narrow-row cotton production in the Mississippi Delta. Several field studies have been initiated in Mississippi since 1989 to determine the feasibility of narrow-row cotton production. Included in these studies were nitrogen (N) management, planting patterns, planting dates, plant growth regulators, potassium (K) rates and placement, and varieties. only the N management component will be included in this report. The major objectives of the study included 1) determination of optimum N management by evaluation of N rates and application schedules; 2) field evaluation of PIX (mepiquat chloride) plant growth regulator; and 3) evaluation of plant characteristics and yield by plant mapping using COTMAP and PMAP to summarize the data. This report will focus on objectives 1 and 2 with an additional discussion of the mapping data to follow in a subsequent report. Urea-ammonium nitrate solution (32% N) was applied either 100% preplant (PP) or 50% PP and 50% as a sidedress (SD) application at early bloom. The N rates were 90, 120, and 150 lb/A knifed in on either side of the row. PIX was applied to one-half of the plot each year with rates of 4-6 oz/A. In 1989 and 1990, lint yields were significantly higher (112 and 98 lb/A, respectively) for 30-in row cotton compared to 40-in rows when averaged over all N treatments. In 1991 and 1992, there was no significant difference between row spacings. Over the 4-year duration of the study, the yield increase has averaged 54 lb lint/A/yr (range from -46 lb/A to +112 lb/A) or an average annual increase of 4.74% for 30-in rows. Increasing N rates from 90 to 120 or 150 lb N/A has not significantly increased lint yields. In most years, as N rate increased lint yields from 30-in rows remained the same or decreased slightly while 40-in row yields decreased significantly. With this in mind, comparisons of 30-in rows with 40-in rows at a specific N rate gave different outcomes. By comparison with 4-year means, at 90 lb N/A applied 100% PP 40-in cotton produced 1192 lb lint/A and 30-in cotton, 1178 lb lint/A. However, if the same comparison is made at 150 lb N/A, 30-in rows produced an average of 142 lb lint/A more than 40-in rows. This net difference between 90 lb N/A and 150 lb N/A is 156 lb lint/A. At the same time, the additional 60 lb N/A produced 14 lb lint/A more in 30-in rows and reduced 40-in row yields by 142 lb lint/A. Split applications of N did help to reduce the large differences between 30-in and 40-in rows. Plant mapping data was taken at harvest from these plots in 1990, 1991, and 1992, and will be used to evaluate potential differences in fruiting patterns and growth characteristics. This information will be briefly summarized in a later report.





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Document last modified July 8, 2004