Fall tillage reduced nutrient loads from liquid manure application during the freezing season

Authors: STOCK, MELANIE - Utah State University; ARRIAGA, FRANCISCO - University Of Wisconsin; Vadas, Peter; GOOD, LAURA - University Of Wisconsin; Casler, Michael; KARTHIKEYAN, K. - University Of Wisconsin; ZOPP, ZACHARIAH - University Of Wisconsin

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/14/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary: Reducing agricultural nutrient loss in runoff is important year-round, but especially from fields that have manure applied in the winter. Fields in no-till management are typically associated with less runoff, but tilling fields may reduce winter runoff from frozen soils by increasing surface depressional storage of water and increasing infiltration. We monitored nutrient loss in winter runoff for two years from field plots in Wisconsin with and without tillage and having manure applied either in December or late January. Nutrient loss was less on chisel-plowed versus untilled plots during both monitoring years. Loss was also less from manure applied when soils were not fully frozen, which allowed greater water infiltration. Wintertime manure applications pose a risk for nutrient loss, but tillage and timing applications to thawed soils can help reduce that loss.

Technical Abstract: Reducing agricultural runoff is important year-round, particularly on landscapes that receive wintertime applications of manure. No-tillage systems are typically associated with reduced runoff loads during the growing season because of macropore development and aggregate stability. In contrast, surface roughness from tillage may aid the infiltration process of frozen soils by providing surface depressional storage. The timing of winter manure applications within tillage systems may also affect runoff depending on snow and soil frost conditions. Therefore, the objective of this study was to evaluate runoff and nutrient loads during the freezing season from combinations of tillage and manure application timings. Six management treatments were tested in south-central Wisconsin during the winters of 2015–16 and 2016–17 with a complete factorial design: two tillage treatments (fall chisel plow versus no-tillage) and three manure application timings (early December, late January, and unmanured). Nutrient loads were lower on chisel-plowed versus untilled soils during both monitoring years. Loads were also lower from manure applied to soils with less frost development. Wintertime manure applications pose a risk to surface nutrient losses, but tillage and timing applications to thawed soils can help reduce loads.