Document: MEL-3-61-7

Impacts of different farm management practices on nitrogen pollution of ground and surface water in Central California: Evaluation and application of BGC ecosystem model.

MULITSCH, M.J.*, L.L.PIERCE, F.G.WATSON and W.B.NEWMAN

California State University, Seaside, CA, 93955 ¹

Abstract:
One of the most important environmental issues facing Central California is surface and groundwater N pollution. These high levels of N in many watersheds of the Monterey Bay, CA are derived from agricultural production. Addressing this issue requires understanding the impact of current farm management practices on N leaching, but many empirical studies are limited by time and resource constraints. The BGC ecosystem process model was adapted to Monterey Bay agricultural conditions and then used to predict short to medium-term effects of lettuce production, cover crops, and vegetative buffer strip usage on N pollution of ground and surface water. Simulation results suggest that aboveground C production, or lettuce yield, and N leaching predicted by the model provide a good relationship with field measured data. Results suggest that cover crops planted during the winter fallow period can reduce soil N leaching into groundwater. Results also show a relationship between large pulses of N lost from agricultural systems during initial rain storms in the fall due to accumulated soil N during the spring and summer months. Although cover crops may not be planted at the time of initial rains, other farm management practices such as planting riparian or grass vegetative buffer strips between farm fields and waterways can effectively remove N from groundwater and surface runoff. A combination of cover crops and vegetative buffer strips may have significant effects on N lost from these agricultural systems.

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This abstract is being presented at: 3:45 PM in session:
Oral Session #49: Linkages Between Land and Streams.