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Manipulation of crowding stress in corn
Abstract
Competition in corn crop was studied through manipulation of crowding (density and spacing) and assimilate supply in several experiments conducted in 1986-1988. Growth and yield responses of 2 hybrids differing in maturity period and prolificacy were studied in a wide range of densities. Under favorable condition, Agway 584S (single-ear, late maturity) out yielded Cornell 281 (multiple-ear, early maturity). Higher yield in Agway 584S was attributed to heavier kernels compared to Cornell 281, which resulted from a longer grain filling duration. Growth analysis indicated that crop growth rate as well as net assimilation rate were greater in Cornell 281 than in Agway 584S. Higher crop growth rate in Cornell 281, however, was directed toward tiller production with no fertile ears. Agway 584S maturing later had longer growth duration contributing to its higher yield than Cornell 281. Intensity of competition was quantified by comparing the grain yield and its components to "isolated" plants. Yield per plant decreased 75% and 80% compared to isolated plants in Agway 584S and Cornell 281 respectively, as density increased from 3 to 12 plants m$\sp{-2}$. Number of kernels per row in Agway 584S and number of productive ears per plant in Cornell 281 were found to be the most sensitive yield components. The timing of competitive stress was investigated by removal of alternate plants at different stages of growth. Most of the competition within the corn canopy occurred during the period between vegetative stage and anthesis. Adjustment in grain yield in response to releasing the competition pressure occurred primarily through increase in kernel number in Agway 584S and number of productive ears per plant in Cornell 281. Artificial shading (50% light reduction) showed that reduction in yield in high densities is due to reduction in photosynthesis rate caused by mutual shading and also by lengthening of the intervals between anthesis and silking. Density-light relationships in six corn hybrids having different leaf orientation indicated that hybrids with upright leaves had some yield advantages over horizontal leaf hybrids in favorable climatological conditions when high densities are used. Results supported the model proposed by Duncan (Crop Sci., 1984) that a linear relationship exists between the logarithm of yield per plant and crowding.
Subject Area
Agronomy|Ecology
Recommended Citation
Hashemi-Dezfouli, Abolhassan, "Manipulation of crowding stress in corn" (1990). Doctoral Dissertations Available from Proquest. AAI9110151.
https://scholarworks.umass.edu/dissertations/AAI9110151