Simulating soybean productivity under rainfed conditions for major soil types using APEX model in East Central Mississippi
Knowledge of soybean yield constraints under rainfed conditions on major soil types in East CentralMississippi would assist growers in the region to effectively utilize the benefits of water/irrigation man-agement. The objectives of this study were to use the Agricultural Policy/Environmental eXtender (APEX)agro-ecosystem model to simulate rainfed soybean grain yield (GY) for nine major soils during 14 years(2002–2015) and then to evaluate selected model inputs/outputs in relation to irrigation managementthat may decrease difference in simulated GY among the different soils. Values for GY ranged broadlyfrom 2.24 to 6.14 Mg ha-1across soils and years, giving a maximum yield difference of 3.90 Mg ha-1. Forthe average GY of nine soils, the range was from 3.52 to 5.42 Mg ha-1over 14 years. Averaged across14 years, GY ranged from 3.66 to 4.90 Mg ha-1across the nine soils and was affected by difference insoil texture (clay and sand percentages) and soil available water content (AWC). Simulations revealedrelatively high water stress during the R4, R5 and R6 stages of plant development (early- to mid-fruitdevelopment), suggesting great potential to enhance soybean yield if some irrigation is provided duringthese critical water stress periods; whereas, the potential was accordingly less in the normal and wetyears. Results indicated installing irrigation on Griffith, Sumter or Demopolis soils would have a largeimpact through increased crop productivity and yield stability.