|FRANCESCONI, W - International Center For Tropical Agriculture (CIAT)|
|WILLIAMS, C - Natural Resources Conservation Service (NRCS, USDA)|
|WILLIAMS, J - Texas Agrilife Research|
|JEONG, J - Texas Agrilife Research|
Submitted to: Journal of Fertilizers & Pesticides
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2016
Publication Date: 3/10/2016
Publication URL: http://handle.nal.usda.gov/10113/62889
Citation: Francesconi, W., Williams, C.O., Smith, D.R., Williams, J.R., Jeong, J. 2016. Phosphorus modeling in tile drained agricultural systems using APEX. Journal of Fertilizers & Pesticides. 7(1):166. doi:10.4172/2471-2728.1000166.
Interpretive Summary: Phosphorus lost from tile drained agricultural fields may be contributing to algal blooms in surface waters, such as Lake Erie. The purpose of this paper was to evaluate the state of the science in the Agricultural Policy/Environmental eXtender (APEX) model related to surface and tile phosphorus transport. Data from an agricultural field in the St. Joseph River watershed in northeast Indiana were used to compare modeling results. By modeling the agricultural field used in this study, the new modeling equations improved soluble P estimates in surface runoff during the year when corn was grown. However, when soybeans were grown and there was no fertilizer added, the older modeling equations represented the data observed in the agricultural fields better for surface runoff. Similar results were observed for modeling phosphorus loss in tile flow; however, the model was not as accurate in these estimations. Improving the accuracy in the estimation of phosphorus losses from artificial drainage systems is necessary to improve our evaluation of agricultural conservation practices that will improve water quality.
Technical Abstract: Phosphorus losses through tile drained systems in agricultural landscapes may be causing the persistent eutrophication problems observed in surface water. The purpose of this paper is to evaluate the state of the science in the Agricultural Policy/Environmental eXtender (APEX) model related to surface and tile P transport. This was accomplished using data from a monitored corn-soybean rotation field in the St. Joseph River watershed, IN. The estimation of SP in surface runoff and tile flow in APEX includes a user defined linear (based on GLEAMS) and nonlinear (Langmuir) sorption option. The results suggest that the inclusion of the Langmuir isotherm improved (18%) SP sorption estimates in surface runoff during the corn year only when P inputs were added, whereas the linear method was more appropriate during the soybean year when no fertilizers were applied. Similarly, SP estimates in tile flow were improved (30%) when using the Langmuir option during the corn year, though the overall model performance predicting this variable were very poor. Modeling improvements of P partitioning processes in APEX can help predict more realistic outputs. Yet to achieve this in tile flow, water percolation processes need to be improved to reflect preferential flow conditions often found in long-term no-till fields and in soils with high clay content. Greater accuracy in the estimation of the effect of artificial drainage systems, common in the US Midwest, should result in the improved evaluation of agricultural conservation practices in order to examine strategies that could reduce P losses for water quality purposes.