Purpose
As large dairies move into western Minnesota, a consistent supply of manure is available that was not historically present. These dairies are using a new technology to separate solids from liquids in the manure, and the impact on nutrient availability in this region’s climate and soil types is unknown. Understanding this is particularly important for sugarbeet growers in the region as late season N availability in the soil affects sugar content of the crop (high late season soil nitrate levels typical result in reduced sugar production). Where in the crop rotation should this manure be applied to maximize the beneficial properties while minimizing risk?
What Did We Do?
A three-year crop rotation including sugarbeet, corn, and soybean was set up at two locations (west central and northwestern Minnesota) with each crop present each year (Figure 1) and then rotated accordingly in subsequent years. Two rates of liquid separated dairy manure from a nearby commercial dairy were applied in the first year (in the fall prior to planting of each crop) and compared with standard synthetic fertilizer-only practices (fertilizers were applied each spring prior to planting). The two manure application rates were approximately 15,000 gallons per acre, which supplied approximately 195 pounds first-year available nitrogen per acre, or approximately 10,000 gallons per acre, which supplied approximately 150 pounds of first year available nitrogen per acre. In following years, only commercial fertilizer was applied according to soil test phosphorus and potassium levels or state nitrogen guidelines, considering manure nitrogen credits if applicable, for each crop. At the end of each growing season, yield was determined for each crop. Sugarbeet was also evaluated for sugar content and quality.
What Have We Learned?
The manured treatments typically resulted in similar or higher yields than synthetic- fertilizer-only for corn and sugarbeet during all three years of the rotation. For soybean, yields were significantly decreased by manure application at one site in the first year and generally unaffected at the second site. In the second and third years, there were no differences in soybean yield across nutrient treatments.
Future Plans
This study was conducted in two fields that did not have a recent history of manure application. Since we know that manure is the “gift that keeps on giving”, we want to repeat this study to see if there are long-term effects of nitrogen release from repeated applications of manure. Thus, manure was applied after the third growing season of the rotation and the rotation will begin again at both sites.
Authors
Presenting & corresponding author
Melissa L. Wilson, Associate Professor and Extension Specialist, University of Minnesota, mlw@umn.edu
Additional Information
Search for manure research: https://www.sbreb.org/research/
Acknowledgements
Thanks to the Sugarbeet Research and Education Board of Minnesota and North Dakota for funding this work.
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