Journal Article

Impacts of Watershed Characteristics and Crop Rotations on Winter Cover Crop Nitrate-Nitrogen Uptake Capacity within Agricultural Watersheds in the Chesapeake Bay Region

McCarty, Gregory W., Lee, Sangchul, Yeo, In-Young, Sadeghi, Ali M., Hively, W. Dean, Lang, Megan W.

2016

Overview

The adoption rate of winter cover crops (WCCs) as an effective conservation management practice to help reduce agricultural nutrient loads in the Chesapeake Bay (CB) is increasing. However, the WCC potential for water quality improvement has not been fully realized at the watershed scale. This study was conducted to evaluate the long-term impact of WCCs on hydrology and NO3-N loads in two adjacent watersheds and to identify key management factors that affect the effectiveness of WCCs using the Soil and Water Assessment Tool (SWAT) and statistical methods. Simulation results indicated that WCCs are effective for reducing NO3-N loads and their performance varied based on planting date, species, soil characteristics, and crop rotations. Early-planted WCCs outperformed late-planted WCCs on the reduction of NO3-N loads and early-planted rye (RE) reduced NO3-N loads by ~49.3% compared to the baseline (no WCC). The WCCs were more effective in a watershed dominated by well-drained soils with increased reductions in NO3-N fluxes of ~2.5 kg N·ha-1 delivered to streams and ~10.1 kg N·ha-1 leached into groundwater compared to poorly-drained soils. Well-drained agricultural lands had higher transport of NO3-N in the soil profile and groundwater due to increased N leaching. Poorly-drained agricultural lands had lower NO3-N due to extensive drainage ditches and anaerobic soil conditions promoting denitrification. The performance of WCCs varied by crop rotations (i.e., continuous corn and corn-soybean), with increased N uptake following soybean crops due to the increased soil mineral N availability by mineralization of soybean residue compared to corn residue. The WCCs can reduce N leaching where baseline NO3-N loads are high in well-drained soils and/or when residual and mineralized N availability is high due to the cropping practices. The findings suggested that WCC implementation plans should be established in watersheds according to local edaphic and agronomic characteristics for reducing N leaching.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Agricultural land / Agricultural management / Agricultural practices / Agricultural production / Agricultural watersheds / Agriculture / Agronomy / Anaerobic conditions / Biology and Life Sciences / Coastal plains / Conservation / Conservation practices / Corn / Cover crops / Creeks & streams / Crop Production - methods / Crop residues / Crop rotation / Cropping systems / Crops / Denitrification / Ditches / Drainage ditches / Earth Sciences / Ecology and Environmental Sciences / Environmental aspects / Farmlands / Fluxes / Glycine max - growth & development / Groundwater / Harvest / Hydrologic models / Hydrology / Influence / Irrigation / Laboratories / Leaching / Mid-Atlantic Region / Mineralization / Nitrates / Nitrogen / Nitrogen - metabolism / Nitrogen Cycle / Nitrogen oxides / Nutrient loading / Planting date / Quality control / Remote sensing / Research and Analysis Methods / Rivers / Rye / Seasons / Simulation / Soil - chemistry / Soil characteristics / Soil conditions / Soil profiles / Soil properties / Soil water / Soils / Soybeans / Statistical methods / Streams / Summer / Water quality / Watersheds / Winter / Zea mays - growth & development