Tillage and herbicide indices illustrate relationships among cropping systems
Farming systems based on reduced inputs and increased diversity of crop types are of interest to producers as alternatives to conventional systems. Indices can be derived to estimate the impact of various farming practices on the system and its environment. The paper presents methods for calculating simple, weighted and modeled herbicide and tillage indices. The simple indices are based solely on farm input use records. The simple indices illustrated in the paper are number of herbicide applications and number of tillage operations. The weighted indices incorporate some knowledge about the operations using external data sources. The examples illustrated are herbicide active ingredient and cumulative disturbance. The third level of complexity is to model the impact of the operations on the environment using several external sources. The paper calculates environmental exposure to herbicides and residue removed. All indices are calculated for nine cropping systems included in the Scott Alternative Cropping System Study. Each index ranked the cropping systems differently. Number of herbicide applications underestimated the relative amount of active ingredient applied in the high input systems as compared to the reduced input (minimum tillage) systems. The types of herbicide necessary to control weeds in high input systems tended to result in higher environmental exposure to herbicides. The number of tillage passes also underestimated the relative amount of disturbance in the high input systems as compared to the organic systems. The amount of residue removed in the organic and high input systems was similar.
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