Reducing the risk of crop injury due to soil-applied herbicides

Soil-applied herbicides are valuable tools: they control early season weeds and, if they are residual, can provide season-long control. However, miscalculations in the use of soil-applied herbicides could cause crop injury or fail to control weeds. Montana producers know that losing a crop due to lack of rain is an unfortunate but inevitable experience. Losing a crop due to herbicide injury could be as bad as a weather calamity, but it can be prevented. Indeed, uncertainty with soil residual herbicides remains a chief obstacle for diversifying dryland cropping systems in Montana to include broadleaf crops such as pea, lentil, canola and sunflower.

To minimize the risk of herbicide-injured crops, we need to understand how herbicides function and the several factors that affect their activity. For example, the soils of Montana are unique in that they have lower organic matter and higher pH than is typically encountered outside this region. Also, many times Montana’s soils are different than those where herbicide residue studies have occurred and upon which current recommendations are based.

For the last 3 years, researchers and graduate students at Montana State University have been evaluating the potential damage that soil-applied herbicides could cause in crops. To determine the best way to maximize the benefits of soil-applied herbicides while avoiding herbicide carryover and crop injury we have assessed carryover effects on different crops and soil types across Montana have been assessed.

This information has been compiled in this web-site to provide agricultural professionals across the State with the necessary tools to prevent and diagnose herbicide injuries. The information presented here include: 1) a link to a 3-step key to assess herbicide injuries developed by the University of Wisconsin, 2) a Power Point presentation summarizing our research, 3) a series of high quality photos showing the responses of twelve crops to several soil applied herbicides, and 4) a PDF document that provides an overview of the factors that influence the fate, effectiveness, and persistence of soil applied herbicides. Collectively, this information will assist you in the development of integrated weed management in agricultural fields.