One-Dimensional Modeling of Crop Production With Topography Corrected Infiltration.

Topography plays an important role in rotational agricultural systems in Michigan. For instance, water re-distribution and water storage along a toposequence highly depend on the topographical position. Along the toposequence, summit and slope positions are typically exposed to water losses due to surface run-off and subsurface lateral flow, while depression areas could gain from run-on water and subsurface lateral inflow. Current crop simulation programs SALUS has been developed to describe one-dimensional water, heat and nitrogen transport for multiple crops. Due to 1-D concept the model is not capable to account for topography in soil water re-distribution. To overcome this model limitation and to improve model performance an approach was developed that corrects infiltration rates used as input by SALUS model based on precipitation, topography and soil properties. The correction procedure included: (i) separating precipitation data into rainfall events; (ii) grouping the events based on rainfall duration, intensity, peak time and intensity; (iii) predicting infiltration for each specific topographical location for each group of rainfall event using KINEROS model, (iv) correcting daily precipitation data of SALUS model with respect to the topographical location and precipitation depth based on results of KINEROS simulations.

To test the approach we used a 6-year experimental data that includes 10 fields, 3 management systems (conventional, reduce input, and organic), and 3 topographical positions (summit, slope, and depression). The experiment is a rotational system with 3 crops (corn, soybean, and wheat). Elevation values in these fields range from 272 to 290 m.a.s.l. and predominant soil textures are sandy-loam, sandy-clay-loam, and sandy-clay. Results of simulations showed that the correction of infiltration improved overall accuracy of the SALUS model in predicting soil water content and crop yield in years with high frequency of intensive rainfall events during growing period.