LIGHT INTERCEPTION AND LINT YIELD OF NARROW-ROW COTTON

Narrow row spacings in crops can potentially increase total seasonal light energy interception. Our objective was to determine the effects of a combination of row spacing vith different genotypes on light interception and yield of upland cotton (Gossypium hirsutum L.). In 1989 and 1990, an okra-leaf genotype and its normal-leaf isoline were grown in the field, using 0.5-m (narrow) and 1.0-m (wide) row spacings in early and late plantings each year. The photosynthetic photon flux density (PPFD) intercepted by the canopy was determined weekly and insolation interception calculated. Aboveground dry matter accumulation and leaf area were determined at rive intervals throughout the season. Open bolls were counted, harvested, and their lint yield determined. Narrow row spacing increased seasonal insolation interception in both leaf types. Narrow rows increased the yield of the okra leaf over that of wide rows in both plantings in 1989 and for the late Planting in 1990. Yield of the normal leaf was reduced by narrow rows in one environment, but not significantly affected by row spacing in three other environments. For okra leaf planted early or late and for the normal leaf planted late, variation in lint yield was strongly correlated with total seasonal insolation intercepted. The yield increase of the okra leaf grown in narrow rows was a result of an increase in the number of mature fruit produced per unit ground area and not an increase in fruit size. Narrow rows increased the efficiency of PPFD interception by a given leaf area. The use of narrow-row culture for the okra-leaf type provides an opportunity for overcoming its low leaf area, increasing its insolation interception, and increasing its lint yield.