Response of Winter Manure Application to Surface Water Quantity and Quality from Small Watersheds.

Manure application on frozen soils may cause potential water quality threats. This study was conducted to assess the impacts of manure application during winter months when the soil is frozen, on water quantity and quality problems from small watersheds: south (SW), east (EW) and north (NW) managed with a corn (Zea mays L.)-soybean (Glycine max L.) rotation in South Dakota. The SW and NW watersheds were used as treatment, and EW as control watershed. The treatments included manure application on the upper half of the SW and lower half of the NW. The soil in the three watersheds was Moody silty clay loam. Surface runoff samples were collected from 2011 through 2014 for water quality analysis. Results showed that nutrient loss from the surface runoff were higher in NW compared to that in SW due to the fact that manure placement in NW was near the outlet. Cumulative (2011-2014) runoff was higher from EW followed by SW and NW. The NW and SW received 70 and 20%, respectively, less cumulative runoff than EW. This shows that manure application increased soils organic matter, improved infiltration and allowed less runoff. Further, SW had the least nitrate nitrogen loss compared to other watersheds. The phosphorous losses (0.2-17 ppm) from runoff samples were higher in 2011 as the precipitation was 14% higher than the long-term average (670 mm). Data from this study showed that the manure application impacts runoff and water quality, hence, improved application of manure management is needed to improve runoff quality.