Environmental quality research in the Beasley Lake watershed, 1995 to 2007: Succession from conventional to conservation practices

Abstract

Abstract:The Beasley Lake watershed (BLW), established for the Mississippi Delta Management Systems Evaluation Area project, represents the US Mississippi Delta region in the national Conservation Effects Assessment Project. The 915-ha (2,260-ac) BLW drains into an oxbow lake that has been monitored since 1995 when row crops were grown on 79% of the area, and the remaining area included a 25-ha (62-ac) lake and a 135-ha (330-ac) riparian forest. Currently, row crops account for 66.5% of the area with 12.4% enrolled in the Conservation Reserve Program. Cotton (Gossypium hirsutum L.) acreage has decreased from 63.3% to 8.9%. Historical and current research in BLW focuses on monitoring lake limnology, evaluating conservation practice effects on edge-of-field runoff, quantifying changes associated with the Conservation Reserve Program, and modeling watershed responses. Applying combinations of conservation practices can significantly reduce nonpoint source pollution. For example, converting row crops to reduced tillage and transgenic herbicide-resistant crops in BLW reduced suspended sediment (70% reduction), total phosphorus (41% reduction), and pesticide concentrations in lake water. Corresponding increases in Secchi visibility (97%) and chlorophyll a (a primary productivity indicator) likely contributed to improved fish productivity (e.g., fish weight increase comparing 1998 and 2004: Micropterus salmoides 87%, Lepomis macrochirus, 65%) during this period. Additional studies should quantify effects of individual practices and improve modeling tools for making better management decisions. The utilization of the Annualized Agricultural Non-Point Source (AnnAGNPS) model and the Riparian Ecosystem Management Model (REMM) together provides additional information on the effectiveness of conservation practices within the watershed by combining technology that assesses riparian buffer effectiveness in filtering nutrients at the field scale with the watershed water quality transport capabilities of the AnnAGNPS model.

Influence of integrated watershed-scale agricultural conservation practices on lake water quality

“…Other studies have tried to assess the effects of combined BMPs on sediment reduction, but again only at the field scale (Zeimen et al 2006). Fewer studies have attempted to assess these BMPs at a watershed scale (Cullum et al 2006;Locke et al 2008;Zablotowicz et al 2006;Yuan et al 2008;Makarewicz et al 2009). The current study observed continuing improved lake surface water conditions with combined implementation of a variety of BMPs from structural localized edge-of-field practices in 1996 and 2006, to watershed-wide cultural practices such as reduced tillage in 2001 and watershed-wide structural practices such as the CRP in 2003.…”

“…Several of the implemented BMPs were chosen specifically to target reductions in soil erosion and concomitant sediment runoff (Cullum et al 2006;Locke 2004;Locke et al 2008;Cullum et al 2010). As a result, it was predicted that Beasley Lake TSS concentrations would decrease after implementation.…”

“…In 1996, about 2.7 ha (6.7 ac) of a structural edge-of-field BMP were implemented that incorporated vegetative filter strips comprised of switchgrass (Panicum virgatum L.) or fescue (Festuca arundinacea [Schreb. ]), and in 2001 an additional 3.4 ha (8.3 ac) were implemented that incorporated vegetative filter strips comprised of bahia grass (Paspalum notatum Flugge) (Locke 2004;Locke et al 2008) (figure 1). This early structural BMP was implemented to reduce suspended sediment loads and accompanying contaminants (e.g., phosphorus [P] and pesticides) from entering the lake.…”

A decade of conservation effects assessment research by the USDA Agricultural Research Service: Progress overview and future outlook

“…Changes in rotations and tillage systems are accompanied by changes in nutrient and pest management, and water quality responses will lag behind any changes in management (Meals et al 2010). One example was given by Locke et al (2008) who described agricultural changes in the Beasley Lake Watershed, which included drastic changes in amounts and types of agrichemical use over a 15-year period and a significant increase in conservation cover.…”

“…Invertebrates, fish, and algae are the three components of aquatic ecosystems most recognized by the general public. Although there is an abundance of literature on the effects of conservation practices on agricultural pollutants (Dinnes et al 2002;Hansen et al 2007;Osmond et al 2012), and we can simulate these benefits (Arabi et al 2008), much less has been published on measured ecological responses (Locke et al 2008;Maret et al 2008;Bosch et al 2009;Smiley et al 2009). This implies a working assumption that if agricultural pollutants are reduced aquatic ecology and biodiversity will improve.…”