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This article in AJ

  1. Vol. 79 No. 1, p. 42-47
     
    Received: Aug 30, 1985


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doi:10.2134/agronj1987.00021962007900010010x

Application of GOSSYM to Yield Decline in Cotton. I. Systems Analysis of Effects of Herbicides on Growth, Development, and Yield1

  1. V. R. Reddy,
  2. D. N. Baker,
  3. F. D. Whisler and
  4. R. E. Fye2

Abstract

Abstract

Cotton (Gossypium hirsutum L.) yields have declined since 1965 despite improvements in technology and introductions of higher yielding cultivars. Cotton scientists have been unable to identify exact causes of the yield decline. One suggested cause is the increased use of herbicides and their toxic effects on root growth in the herbicide incorporated zone. In this study, the computerized crop simulation model, GOSSYM, was used to predict cotton performance under several levels of herbicide-induced root reduction under various environmental conditions in a Leeper clay loam soil (fine, montmorillonitic, nonacid, thermic Vertic Haplaquept). The model predicted a small increase in yield when root reduction was moderate and at shallow depths. However, when the depth of root reduction increased to 200 mm or the percentage of root reduction increased, there was a predicted decrease of up to 40% in cotton lint yield. This decrease in lint yield was much larger when decreased root length was combined with reduced soil water permeability in remaining roots. Predicted yield was also reduced under unfavorable weather conditions. With increase in the depth of root reduction or increase in the percentage of root reduction and with permeability reduction there was a decrease in the root growth throughout the season. Increased N and water shortages were apparent with increase in the depth or level of root reduction. It was concluded that improper application of herbicides was one of the contributing factors for the cotton yield decline.

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