(Field 5C)
James Bordovsky, Doug Nesmith, Steve Jackson, Stacey Ontai and Joe Mustian

Objective: To determine the effect of row spacing and cotton variety on lint yield with the expectation of improving water use efficiency.

Methodology: The field experiment was similar to last year’s study. Cotton varieties, Paymaster 2326RR and Paymaster 2156RR, were flat planted into 20 acres of terminated rye. Four blocks of each variety were planted at row spacings of 7.5 inches (120,000 seed/ac), 15 inches (100,000 seed/ac), and 30 inches (70,000 seed/ac) with a John Deere 1730 Max Emerge narrow row planter. Each treatment plot was 40 ft wide and ranged in length from 200 to 1300 ft oriented in an east-west direction. Seasonal irrigations totaling 13.3 inches were applied with LEPA applicators spaced every 5 ft along the length of the pivot. Nitrogen was applied with seasonal irrigations, P2O5 applied prior to planting rye on 14 January. Rainfall from planting until irrigation termination totaled 1.4 inches. A growth regulator was applied on 11 June after young cotton plants were accidentally burned by chemicals on 6 June. Hand-harvested samples were collected to determine lint yield.

Results: Within the Paymaster 2156RR variety, the 15-inch spacing produced significantly higher yields at 1965 lb lint/ac than the 30-inch spacing at 1748 lb lint/ac (Table 1). This was a 12% increase in yield with no increase in inputs other than higher seed population. Row spacing did not significantly affect lint yields in the Paymaster 2326RR variety. Similar to last year, Paymaster 2156RR produced significantly higher lint yields than Paymaster 2326RR at all row spacings. In dry growing seasons, lint yields appear to be affected more by the cultivar planted than by row spacing or plant population.

Table 1. Row spacing effect on cotton lint yield (lb/acre) of two cotton varieties.
*Means followed by the same letter in the same row are not significantly different (P<0.05 LSD)