Do cover crops reduce the leaching risk of soil legacy phosphorus in agricultural watersheds?

Session: Soil Health: Role on Nutrient Losses from Agricultural Soils (1)

Liguang Li, University of Notre Dame, [email protected]
Jennifer Tank, University of Notre Dame, [email protected]
Sheila Christopher, University of Notre Dame, [email protected]
Ursula Mahl, University of Notre Dame, [email protected]
Todd Royer, Indiana University, School of Public and Environmental Affairs, [email protected]

Abstract

In the agricultural Midwest, decades of farming and associated fertilizer application have resulted in phosphorus (P) accumulation in soils.  This legacy P is available to cash crops but also complicates efforts to reduce P runoff from fields to adjacent freshwaters.  Presently, the effects of agricultural conservation practices on legacy P in soils are understudied. We examined the effects of the watershed-scale planting of cover crops on soil P in the Shatto Ditch Watershed (Kosciusko Co, IN), where fertilizer P is no longer applied due to high legacy P in soils. Over four years, we sampled soils each fall and spring in nine fields with cover crops (CC) and four fields without cover crops (NoCC).  We found that multiple P species, soil P storage capacity, organic matter content, and pH, Manganese, Iron differed between CC and NoCC fields. Cover crop strengthed the relationship between the change of SPSC and Mehlich P, Bray P. Cash crop residue increased soil nutrient concentration during winter, due to uptake by CC, change of Bray P and water extractible P (WEP) were negative in CC fields, but positive in NOCC fields. This indicated that CC reduced the risk of P leaching from fields to waterways during