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Development of tools for evaluating herbicide injury to corn
Abstract
Herbicide phytotoxicity to corn is commonly documented by visible observations, however visible symptomology may not reflect physiological responses. A portable photosynthesis system was utilized for measuring photosynthesis and stomatal conductance of four 'Pioneer' corn hybrids treated with postdirected applications of sethoxydim. Photosynthesis measurements were compared with non-physiological measurements for ability to detect sethoxydim related stress and injury to corn. Sethoxydim is a herbicide used to control monocot species, and can be used as a postemergence-directed treatment in corn to control grassy weeds. The corn growth and yield model CERES-Maize (V 1.0) was modified to respond to herbicide induced grain yield reductions by incorporating a herbicide stress factor and the duration of this stress into calculation of the daily biomass production. The modified version of CERES-Maize was calibrated with field data from 1988 and was tested with independent field data from 1989. The results of the field research indicated that sethoxydim reduced net photosynthesis of four corn hybrids for 10 to 30 days. This reduction in net photosynthesis could be detected within one day after sethoxydim was applied. Herbicide stress was defined as the difference in net photosynthesis between sethoxydim treated and non-treated plants. Total herbicide stress was defined as stress intensity (percent reduction in net photosynthesis) times the duration of the stress. Total herbicide stress was highly correlated with grain yield. Visible injury evaluations, measurements of plant height, lodged or barren plants, kernels per ear, and kernel weight were not correlated with grain yield. In the dryland environments, sethoxydim did not affect corn yields. With irrigation, grain yields of hybrids 3475, 3377, and 3379 were reduced by 11, 12, and 15% respectively, by sethoxydim at 220 g ha$\sp{-1}$ applied at either V7 or V11 growth stages. Hybrid 3183 did not respond to any sethoxydim treatment. Net photosynthesis measurements detected corn response to sethoxydim without any externally visible effects. The model was able to predict grain yield of all treatments within 20% of actual measured values and was within 10% for most hybrids and sethoxydim treatments.
Subject Area
Agronomy
Recommended Citation
Smart, James Robert, "Development of tools for evaluating herbicide injury to corn" (1991). ETD collection for University of Nebraska-Lincoln. AAI9208114.
https://digitalcommons.unl.edu/dissertations/AAI9208114