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 reduce 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 Summer 2013, prior to the increase in CC planting, when cash crop growth was peaking, soil NO₃^--N was significantly higher in CC fields versus non-CC treatments (ANOVA, p=0.0003) and there was an inverse relationship between soil and tile drain NO₃^-N suggesting that soil NO₃^-N retention may prevent leaching to tile drains. In Fall 2013 and Spring 2014, when increased CC plantings were actively growing on fields, soil NO₃^-N was lower in CC fields compared to those without (ANOVA, p=0.02) suggesting that N may be tied up in CC tissue during Fall and Spring. In contrast to NO₃^-N, there were no significant CC effects on soil P content, nor was soil P related to tile drain dissolved reactive P in any season. Given these results, year-round study of soil and tile drain chemistry is warranted in order to definitively link soil and water quality benefits of CC.