Linking Soil Health to Improved Water Quality Via the Planting of Cover Crops in the Shatto Ditch Watershed, Kosciusko Co, in.

Tile drainage systems are common in the Midwestern U.S. and can transfer excess fertilizer nutrients from agricultural soils to adjacent streams and ditches, especially when field are bare. The planting of winter cover crops (CC) offers a potential management strategy to improve soil health while reducing nutrient leaching from fields to tile drains.  We are quantifying the influence of CC on soil and water quality at the watershed scale in the Shatto Ditch Watershed (SDW). During Fall 2013, we increased CC coverage from ~12% (321 acres) during the pre-treatment year to ~67% (1610 acres) and are measuring the effect of CC planting on soil nutrients. We are also investigating whether there are predictable relationships between soil quality and tile drain nutrient leaching. In Fall (2013 and 2014) and Spring (2014 and 2015), when increased CC plantings were actively growing on fields, soil NO₃^-N was lower in CC fields compared to those without (ANOVA, p<0.05 for all seasons) suggesting that N may be tied up in CC tissue during Fall and Spring. There was also a significant release of NO₃^--N and NH₄⁺-N (ANOVA, p<0.05) from pre to post-CC termination, which would be available for cash crop use. There was also a positive relationship between soil and tile drain NO₃^--N suggesting that cover crops could reduce NO₃^--N loss from tile drains. Water extractable phosphorus was lower in cover crop fields compared to those without though these results were not statistically different. We did not observe a significant increase in soil organic carbon in fields with CC during the first two years of our study yet labile soil organic carbon increased in fields that contain CC, suggesting organic matter quality was improving. Given these results, year-round and longer-tern (>2 years) monitoring of soil and tile drain chemistry is warranted in order to definitively link soil and water quality benefits of CC.