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Decision Criterion for Profitable Johnsongrass (Sorghum halepense) Management in Soybeans (Glycine max)

Published online by Cambridge University Press:  12 June 2017

Roland K. Roberts  and
Robert M. Hayes
Roland K. Roberts
Affiliation:
Dep. Agric. Econ. Rural Soc., Knoxville, TN 37916
Robert M. Hayes
Affiliation:
Dep. Plant Soil Sci., Univ. Tenn., Knoxville, TN 37916
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Abstract

A decision criterion is presented for postemergence johnsongrass control in soybeans. Models derived from actual data describing the relationship between johnsongrass density (X) and soybean yield loss are used to develop the decision criterion for soybeans planted in 0.25- and 1-m row spacings. The yield loss equations are L1 = 424–424 exp (-0.023X2) for 0.25-m row spacing and L2 = 643-643 exp (−0.004X2) for 1-m row spacing. When combined with the cost of control (Px) and the expected price of soybeans (Py), these equations can be used to find the density thresholds where johnsongrass control becomes profitable. For the 0.25-m row spacing, this relationship was Px = Py [424–424 exp (−0.023X2) or more simply Px = Py L1, which equates the cost of control to the value of the soybean yield increase from control. The johnsongrass density (X) that satisfies this equality is the threshold (X*) above which control is profitable.

Keywords

Johnsongrass, Sorghum halepense (L). Pers. #3 SORHAsoybeans, Glycine max (L.)Merr.Economic modeleconomic thresholdscontrol thresholdsweed management
Type
Research
Information
Weed Technology , Volume 3 , Issue 1 , March 1989 , pp. 44 - 47
Copyright
Copyright © 1989 by the Weed Science Society of America 

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References

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