LAUSR

In cold regions, nutrient losses from dairy agroecosystems are a longstanding and recurring problem, especially when manure is applied during winter over snow-covered frozen soils. This study evaluated two tillage (fall chisel and no-tillage) and three manure-type [un-manured control, liquid (<5% solids) and solid (>20% solids) manure] management treatments. The liquid and solid manure used in this study were from the same animal species (Bos taurus) and facility. The six management treatments were field-tested in south-central Wisconsin during the winters (November-April) of 2017-18 and 2018-19 with a complete factorial design. Seasonal runoff losses were significantly lower from fall chisel tillage compared to no-tillage during both seasons. Manure applications (both liquid and solid) on top of snow significantly increased most of the nutrients (NH4 + , DRP, TKN and TP) in runoff compared to un-manured control. Irrespective of tillage and multiple runoff events, solid manure was present on the surface for longer periods, potentially releasing nutrients each time it interacted with runoff. In contrast, liquid manure infiltrated the snowpack and was partly lost with snowmelt and infiltrated soil depending upon soil frost and surface conditions. Overall, results indicate that wintertime manure applications over snow-covered frozen soils pose a risk of nutrient loss irrespective of tillage and manure type, but in unavoidable situations, prioritizing tillage × manure type combination can help reduce losses. This article is protected by copyright. All rights reserved.