Influence of crop management on soil moisture and plant stresses

Public awareness about environmental quality has been on the rise for the last few decades. Impact of land use on the environment has been of great importance for decision makers. This paper presents a research study of large watershed crop management impacts on soil, plant, and interdependence pollutant loads using a Geographic Information System (GIS)-based watershed modeling tool called Soil and Wafer Assessment Tool (SWAT). The Tangipahoa River Watershed, LA, was selected as the study area. This research required the use of a continuous time modeling to simulate watershed hydrology, surface and subsurface water quality processes, and the impacts of crop management. The SWAT utilizes the U.S. Geological Survey and Soil Conservation Services geographic raster maps resources. SWAT includes nationwide relational database of soil properties, weather data, and pesticides, fertilizers, and tillage applications. Geographic data were extracted via the Geographical Resources Analysis Support System (GRASS) including digital terrain model, land use, and soil type layers at a scale of 1:250,000 and 500 m resolution. SWAT was applied for several crop management scenarios. There were insignificant differences in soil moisture distributions among the different crop management scenarios because the amount of surface water remained unchanged. However, crop stresses varied within 5%. The use of no-tillage resulted in a 20% reduction in the basin sediment yield, Org-N, and Org-P, but there was an increase in Nitrate-N and soluble-P loads. The simulation of hay gave similar values except Nitrate-N was decreased. Conversely, the simulation of cotton gave an increase in Nitrate-N and soluble-P if compared to the BOC.