EFFECT OF PLANT POPULATION AND ROW-WIDTH ON INSOLATION INTERCEPTION AND LEAF AREA INDEX IN COTTON

J.J. HEITHOLT

ABSTRACT

Plant population density and row spacing can be important factors related to the lint yield of cotton (Gossypium hirsutum L.). In 1991, the effect of selected plant populations in combination with 0.5-m or 1.0-m row spacings was investigated using two isolines of cotton (DES 24-8 normal- and okra-leaf) grown in a field environment. At the first true leaf stage, plots were thinned to either 5, 10, 15, or 20 plants per square meter (20,000, 40,000, 60,000, and 80,000 plant per acre). The plant population exhibiting the highest lint yield was not affected by row spacing but was dependent upon isoline. The maximum lint yield of normal-leaf (1460 kg ha-1) was achieved with 5 plants per square meter whereas the maximum lint yield of okra-leaf (1500 kg ha-1) was achieved with 10 plants per square meter. Averaged across leaf types and populations, the lint yield of 0.5-m rows was 1450 kg ha-1 which was significantly higher than that of the 1.0-m rows (1400 kg ha-1). Averaged across leaftypes, in 0.5-m rows the seasonal insolation intercepted from the 5 plants per square meter spacing was 1995 Mj m-2 and increased to 2220 MJ m-2 when population was 20 plants per square meter (an increase of 225 MJ m-2). Averaged across leaftypes, in 1.0-m rows the seasonal insolation intercepted by 5 plants per square meter was 1880 MJ m-2 but only increased to 2040 MJ m-2 when population was 20 plants per square meter (an increase of 150 MJ m-2). The maximum leaf area index and maximum aboveground dry matter at cutout were measured for both row-spacings and the two lowest plant populations and found to be unaffected by row-spacing and population. Fiber maturity (averaged across isolines) decreased significantly from 76% at 5 plants per square meter to 72% at 20 plants per square meter. In 1992, a similar experiment was conducted using 0.75-m and 1.0-m rows. The plant populations were 2, 3, 5, 10, and 15 plants per squaremeter. For okra-leaf, lint yields were highest at 10 plants per square meter (1150 kg ha-1) regardless of row-spacing. For normal-leaf, the populations of 2, 3, and 5 plants per square meter were all similar for the 0.76-m rows (1120 kg ha-1) and higher than that of 10 and 15 plants per square meter (910 kg ha-1). For the normal-leaf in 1.0-m rows, 3 plants per square meter proved optimal (1190 kg ha-1). Averaged across populations and leaf types, the yield of the 0.75-m rows (1100 kg ha-1) was significantly higher than the yield of the 1.0-m rows (1040 kg ha-1). In general, over the two years, the optimal plant populations were not affected greatly by row-spacing.





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Document last modified July 8, 2004