Impact of soil compaction on 30-year soybean yield simulated with CROPGRO-DSSAT

Soil compaction is a threat to crop yield, but mechanical decompaction operations increase soil degradation risk and crop costs. The decision about soil management practices that minimize yield loss depends on the impact of soil compaction on crop yield. However, the relationship between soil compaction and crop yield is affected by rainfall pattern, which changes over the years. Long-term effect of soil compaction in crop yield is wide unknown, and fill this gap is crucial for adjust soil management to improve soil conservation and increase crop yield. To evaluate the impact of soil compaction on soybean yield over 30 crop seasons using DSSAT CSM-CROPGRO-Soybean model. Soybean yield was simulated in hypothetical soil profiles of sandy loam, silty loam and clay soils and 12 scenarios of soil compaction (contrasting scenarios - from a whole compacted profile to one compacted layer). We also set two hypothetical reduced rooting depths and three levels of reduced root proliferation due to soil compaction by changing the soil root growth factor parameter to mimic the mechanical stress effect on root growth on DSSAT. Simulations were carried out with data (1990 to 2020) from a weather station located in Southern Brazil and with soybean genetic parameters calibrated for the same region. The reduction in soybean yield due to soil compaction estimated by DSSAT was lower than 0.1 Mg ha⁻¹ in simulations with well-distributed rainfall (every 2 weeks or shorter) but it reached 4.1 Mg ha⁻¹ in simulations with periods without rainfall longer than 2 weeks. The simulated cumulative reduction in soybean yield over 30 years due to soil compaction reached up to 39% of the potential yield, of which 77% was associated with the decrease in rooting depth and 21% with the reduction in soil water availability. Thus, a reliable overview of the effect of soil compaction on soybean yield should consider the interactions between soil, plant and weather variables. This work presents a strategy based on DSSAT simulations to assess the relation between crop yield and soil compaction, which is a worldwide demand still fed with scarce data. Researchers, farmers, technicians and decision makers can replicate and improve this strategy to simulate the negative impact of soil compaction on soybean yield and many other crops, which can assist them to adjust management practices to minimize soil degradation and reduce yield gaps.