Combining multi-environmental trials and crop simulation to understand soybean response to early sowings under contrasting water conditions

Abstract

Anticipating sowing date in spring-sown crops is an agronomic strategy often suggested in Europe to escape water and heat stresses during the most susceptible growth periods occurring in early summer. This strategy was evaluated experimentally in soybean (Glycine max (L.) Merrill) by comparing early and conventional sowing dates for a range of cultivars grown in 18 “site x year” environments from southern France between 2010 and 2018. Conventional sowing often resulted in higher grain yields than early sowing, the latter being more favorable to grain size and protein concentration. STICS crop growth model was used to calculate dynamic abiotic (radiation, water, high and low temperatures, nitrogen) stress factors influencing the main crop physiological processes. Ecoclimatic and STICS-based agrophysiological indicators were used in a PLS (Partial Least Squares) regression as explanatory variables of grain yield (r² = 0.33). The key indicators were radiation interception from emergence to maturity, severe stomatal water stress during all the reproductive phase and high temperature since the beginning of grain filling. STICS crop model was used to characterize the 157 “cultivar x site x year x sowing date x irrigation” environments, according to water, heat and cold stresses importance in different phenophases. Then 5 profiles of abiotic stresses emerged from a clustering analysis in two steps by hierarchical ascending classification and K-means. STICS-based environmental characterization was used to explain the relative success or failure of early sowing dates and early-maturing cultivars.