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Waiting for the Weather to Break for New Research

by Wyoming Livestock Roundup

By Jeremiah Vardiman, UW Northeast Area Extension Educator

Like our dry bean producers in the Bighorn Basin, Gustavo Sbatella waited this spring for the weather to let up enough to get his new research trial planted at the University of Wyoming’s Powell Research and Extension Center.

Sbatella is an assistant professor for the University of Wyoming with a focus in irrigated crops and weed management. His new two-year study focuses on herbicide carryover of pre-emergent herbicides used in dry beans and corn cropping systems, where carryover is the amount of herbicide that remains in soil from the previous year.

Pre-emergent herbicides are applied soon after planting but before the crop emerges. They can be incorporated into the soil through water or mechanical means. These soil-applied herbicides are an important tool for our farmers when it comes to fighting herbicide resistant weeds.

You are probably asking yourself, “Why is there interest in herbicide carryover in the soil. Doesn’t the herbicide label tell you that?”

You are correct that the herbicide residual duration is on the label. However, since the degradation of herbicides in the soil is influenced by environmental factors, the time stated in the label is the estimated breakdown under optimal conditions.

Herbicide degradation in soil is mainly the result of hydrolysis and microbial activity, with temperature and soil moisture being the main environmental factors affecting herbicide carryover. Therefore any water shortages, which could result from limited irrigation, drought conditions or others, could provide conditions to make the herbicide remain longer in the soil resulting in affects to the following crop and, depending on the magnitude of the affect, could be partial or total yield loss.

Sbatella has designed a study with 100 percent, 85 percent and 70 percent irrigation levels to mimic various levels of water shortages and to provide enough distinction in the data to identify the effects on herbicide carryover. These irrigation treatments will be applied to dry bean and corn crops that have been treated with the four different pre-emergent herbicides to each crop. Moisture levels within the field will be monitored through data loggers, and soil samples will be utilized to determine herbicide persistence, along with other data such as weed counts and crop yield.

The next growing season in 2016, the corn and dry bean fields will be divided into thirds to plant three rotational crops. Sugarbeets, dry beans and sunflowers will be planted in the corn plot, and sugarbeets, corn and sunflower in the dry bean plots. Moisture levels and soil samples will still be recorded along with herbicide effects and yield for these rotational crops.

Through this study, Sbatella is hoping to provide growers in the Big Horn Basin with pertinent local information regarding herbicide carry over and provide solid baseline data to apply for more grants to move this research project to a larger scale that includes other locations and variables such as tillage.

For more information on this research project, please contact Gustavo Sbatella at the University of Wyoming’s Powell Research and Extension Center at 307-754-2223.

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