| Earlier canopy closure and greater light interception in narrow row cotton (0.50 to 0.76 m row spacing) allows a potentially higher yield as compared with conventional cotton production systems (0.96 to 1.02 m row spacing). However, the increased shading of the leaves that supply assimilates to developing bolls affect the quality of the lint and limit further yield increases. Alterations of canopy architecture using a combination of management and genetic strategies to allow more light penetration into the canopy may be a way to increase the yield of cotton through greater canopy photosynthesis. The objective of this study was to evaluate the response of cotton to row spacing and plant density, and how plant architecture changes affect the light penetration into the canopy and yield of cotton. Two field experiments per year were established in 1995 and 1996. In the first experiment, combinations of row spacing (0.76 and 1.02 m) and plant densities (32,291, 64,582, and 96,873 plants per hectare) were evaluated. In the second experiment, different artificial plant architectures were evaluated. The canopy was modified by removing part of the leaves, mechanical topping, permanent and temporarily opening of the canopy, and trimming of branches. Photosynthetic photon flux density (PPFD) interception, PPFD penetration into the canopy, earliness, dry weight accumulation, yield, and yield components were measured. The 0.76 m rows had an earlier and higher light interception than 1.02 m rows due to a better distribution of plants on the ground. The effect of this behavior on the yield, yield components and earliness depended on the number of flowers per square meter produced early during the flowering period. The production of bolls and yield increased as the plant population increased, up to 64,582 plants per hectare. Also, the high plant population increased the days to 65% open bolls through the effect on the height of the first fruiting branch, number of fruiting positions and, the boll period. The results show that the earlier row closure in narrow row cotton as compared with conventional rows is an important constraint for further yield increase in cotton. Therefore, when the light Penetration into the canopy was increased through early canopy alterations, the boll production and the cotton yield were increased. Cultivars of cotton with short branches, short height, and modified leaves at high plant densities could be a way to increase the yield of cotton. |
