Case study comparison between litigated and voluntary nutrient management strategies

Abstract

The impairment of surface water quality in the United States has been well documented, as has the potential for agriculture to contribute nutrients that accelerate this impairment. In response, widespread implementation of conservation strategies to reduce nutrient losses and mitigate impairment has occurred. This study reports and compares the outcomes of voluntary and litigated conservation and nutrient management strategies in watersheds of Lake Erie and northwest Arkansas, respectively. In the Maumee (MRW) and Sandusky River Watersheds (SRW) that drain into Lake Erie, voluntary strategies to reduce total phosphorus (P) loading from cropland were implemented in the mid-1980s. The strategies focused on reducing particulate P loading through erosion control programs, utilizing no-till and reduced-till management. As various subsidies became available, as well as improved planters and better herbicides, farmers rapidly adopted conservation tillage. Between 1975 and 1995, this led to a decline in fertilizer and manure application and increased conservation tillage acreage, which contributed to a reduction in total and dissolved P export. In the last 10 years, however, increased no-till acres with surface soil P stratification, fall and winter broadcasting of P fertilizer, and more extreme rainfall-runoff events have contributed to an increase in dissolved P export. In the Eucha-Spavinaw Watershed (ESW), northwest Arkansas, litigation required a minimum of 33% of the poultry litter produced be exported out of ESW and the remaining land applications to be based on the risk of P runoff. Use of the Eucha-Spavinaw P Index (ESPI) has decreased the land application of poultry litter from an average 5.6 t ha⁻¹ (2.5 tn ac⁻¹) before litigation to 2.5 t ha⁻¹ (1.12 tn ac⁻¹) in 2009. This, combined with the fact that 70% to 80% of the produced litter was being transported out of ESW, has greatly reduced the risk of P loss in agricultural runoff. At 2009 fertilizer prices, the loss of P and nitrogen (N) from cropped acres in MRW and SRW was US$13 ha⁻¹ (US$5 ac⁻¹), and the value of P and N exported in litter from ESW was US$40 ha⁻¹ (US$16 ac⁻¹). While voluntary implementation of BMPs in Lake Erie watersheds decreased total P export, continued monitoring is needed to adaptively manage these BMPs to ensure their long-term effectiveness. Litigated BMP adoption in northwest Arkansas did reduce land application of litter but at a cost to beef grazing operations, which are symbiotic to poultry operations and had been using litter as a low-cost source of N and P.