Evaluating the Success of Phosphorus Management from Field to Watershed

This paper reviews the characteristics, benefits, and drawbacks of agricultural ditches and wetlands, as well as strategies for applying agricultural best management practices (BMPs) at the watershed scale for improving water quality. This synthesis focuses on the Great Lakes Region and the Mississippi River Basin in the United States, and specifically crop production systems in watersheds with subsurface drainage. The USDA Natural Resources Conservation Service (NRCS) has developed conservation practice standards for open channels and wetlands, which mitigate nutrient and sediment loading to surface water bodies from agricultural lands. Practices that use agricultural ditches to improve water quality, such as the two-stage ditch, have emerged in the last two decades and are starting to see a greater application in the region. Using wetlands as water treatment systems has a long history in a range of settings and over the past several decades is seeing more widespread application in agriculture. Water quality and watershed models are increasingly used to develop watershed strategies for reducing nutrient exports with agricultural BMPs. Models are also helpful in evaluating combinations of practices from the farm scale to the watershed scale. Application and limitations of several models commonly used in these regions of the United States are discussed. Finally, successful conservation strategies at the watershed scale must consider the human dimensions of watershed management, and we summarize the literature in this region on farmer perceptions and adoption of practices.

Section: Best Management Practices At the Watershed Scalementioning

confidence: 99%

Assessment of beyond-the-field nutrient management practices for agricultural crop systems with subsurface drainage

Kalcic¹,

Crumpton²,

Liu³

et al. 2018

“…This is not unexpected given the slow decline in STP even when no P is applied due to the slow release of sorbed P and offtake with harvested forage (Sharpley et al 2007). The lag time between management change and STP response will likely exceed 5 years (McCollum 1991;Sharpley et al 2009b). However, based on data collected by the planning team, the number of fields receiving poultry litter declined from 900 in 2004 to 700 in 2009, which cover only 7% to 6% of the whole ESW (table 2).…”

Section: Figurementioning

confidence: 99%

Case study comparison between litigated and voluntary nutrient management strategies

Sharpley¹,

Richards²,

Herron³

et al. 2012

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 EuchaSpavinaw 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.

“…This work highlighted the difficulty in applying field-scale solutions across a watershed and most importantly, reliably monitoring performance at a watershed scale. Issues such as the lag times between implementation of conservation actions and response of environmental indicators in streams often mask any immediate gain in reduction and may take years of in-waterbody monitoring to detect improvement (Sharpley et al 2009). For example, in-stream concentrations of P can be influenced for years by preexisting P, or legacy P, which can also mask the effectiveness of CPs at the watershed scale .…”

mentioning

confidence: 99%

The utilization of edge-of-field monitoring of agricultural runoff in addressing nonpoint source pollution

Daniels¹,

Sharpley²,

Harmel³

et al. 2018

While basin-scale studies and modeling are important tools in relating land uses to water quality concerns, edge-of-field monitoring (EOFM) provides the necessary resolution to spatially target, design, and evaluate in-field conservation practices for reducing nonpoint source pollution from agriculture. This paper introduces this special issue of the Journal of Soil and Water Conservation, a collection that provides an overview of EOFM on agricultural lands. The issue describes the transition of EOFM from a mainly research endeavor to on-farm monitoring of the environmental impact and performance of agricultural practices and addresses topics such as (1) disconnect between large-scale loading estimates and the prevalence of sound nutrient management practices; (2) obstacles in identifying the causes, sources, and solutions to agricultural nonpoint source pollution; (3) progress evaluation at the watershed scale; (4) need for additional multiscale studies to better understand the fate and transport continuum and establish linkages between EOFM and in-stream water quality; (5) history of EOFM and recent advances; and (6) alternative methods to determine whether EOF results are acceptable. The increased attention on agricultural runoff has concurrently raised awareness of the need for EOFM. It is at the field scale that data are needed to better understand the fate of sediment and applied nutrients and inform adaptive management to mitigate offsite losses. This special issue compiles the latest scientific information related to utilizing EOFM to evaluate and address agricultural nonpoint sources, and provides a glimpse of EOFM in the future.