Soybean and maize simulation under different degrees of soil erosion

Abstract

Erosion–productivity relationships in the black soil region of northeast China have attracted increasing research attention. The effects of erosion on complex crop growth processes are difficult to measure, and the mechanisms of erosion–productivity interactions are still unclear. The objectives of this study were to analyze the effects of soil erosion on crop growth and soil water movement processes, and to analyze the causes of yield reduction, using the Agriculture Land Management Alternatives with Numerical Assessment Criteria (ALMANAC) model. The ALMANAC model was calibrated for soybean and maize using plot experiments conducted in 2006 and 2016. Data from eighteen field sites were selected for model evaluation and the analysis of erosion effects. Soil properties were investigated, and crop growth and soil water content were monitored every ten days from 2011 to 2016. The ALMANAC model accurately simulated crop growth, crop yield, and soil water content under various degrees of soil erosion. Simulated and measured results showed that crop growth and soil water movement were significantly different in soils with different erosion degrees. As the degree of soil erosion progressed from "light" to “moderate” to “severe” erosion, average soybean yields were reduced by −4.2 and 23.5%, average maize yields—10.4 and 25.4%, the maximum leaf area index (LAImax) of soybean—2.0 and 21.9%, the LAImax of maize—1.6 and 13.3%, respectively. The root weights (RW) of soybean and maize decreased by 15.3 and 17.6%, respectively, from "moderate" to "severe" erosion. Simulated water use efficiencies (WUE) for “light,” “moderate,” and “severe” erosion sites were 4.84, 4.97, and 4.66 kg ha−1 mm−1 for soybean, and 24.30, 25.47, and 22.11 kg ha−1 mm−1 for maize, respectively. Transpiration (EP) at soybean sites and evapotranspiration (ET) at maize sites were decreased by 14.8 and 14.0%, respectively, from “light” to “severe” erosion. The parameters for soybean and maize derived in this study are similar to these reported previously, and can be used for sites with similar soils, crop hybrids, and weather conditions. Our results show that once the erosion reached "severe" levels, LAImax, RW, grain yield, and WUE values for soybean and maize were significantly reduced. The primary causes of yield reduction in eroded soils were decreased emergency rate and increased water stress.