PT  - JOURNAL ARTICLE
AU  - D. Maski
AU  - K.R. Mankin
AU  - K.A. Janssen
AU  - P. Tuppad
AU  - G.M. Pierzynski
TI  - Modeling runoff and sediment yields from combined in-field crop practices using the Soil and Water Assessment Tool
AID  - 10.2489/jswc.63.4.193
DP  - 2008 Jul 01
TA  - Journal of Soil and Water Conservation
PG  - 193--203
VI  - 63
IP  - 4
4099  - http://www.jswconline.org/content/63/4/193.short
4100  - http://www.jswconline.org/content/63/4/193.full
AB  - Cropland best management practice recommendations often combine improvements to both tillage and fertilizer application practices to reduce sediment losses with surface runoff. This study evaluated the impact of conventional-till and no-till management practices with surface or deep-banded fertilizer application in sorghum-soybean rotation on runoff and sediment-yield predictions using the Soil and Water Assessment Tool (SWAT) model. The model was calibrated using USDA Natural Resources Conservation Service runoff curve number for antecedent moisture condition II (CNII), saturated hydraulic conductivity, and available water capacity parameters for runoff and USLE cropping factor (Cmin) for sediment-yield predictions for three field plots (0.39 to 1.46 ha [0.96 to 3.6 ac]) with different combinations of practices and validated for three field plots (0.40 to 0.56 ha [1.0 to 1.4 ac]) over a period of 2000 to 2004. Surface runoff calibration required CNII values greater than the recommended baseline values. No-till treatments required slightly greater curve number values than the till treatment, and this difference was similar to that associated with increasing the soil hydrologic group by one classification. Generally the model underpredicted the sediment yield for all management practices. Baseline Cmin values were adequate for treatments with soil disturbance, either by tillage or fertilizer deep-banding, but best-fit Cmin values for field conditions without soil disturbance (no-till with surface-broadcast fertilizer) were 2.5 to 3 times greater than baseline values. These results indicate current model limitations in modeling undisturbed (no-till) field management conditions, and caution that models calibrated for fields or watersheds predominated by tilled soil conditions may not function equally well in testing management scenarios without tillage.