Optimizing wheat (Triticum aestivum L.) management under dry environments: A case study in the West Pampas of Argentina

Abstract

Water shortage, caused by large variations in the amount, frequency and timing of rainfall during the crop cycle, is one of the major abiotic stresses limiting crop production. In this context, environmental variability represents a significant challenge for farmers as optimal management practices vary from season to season. The aim of this study was to optimize wheat (Triticum aestivum L.) management practices considering rainfall variability in the West sandy Pampas of Argentina. This region is characterized by a high annual rainfall variability with predominant summer rainfall and probable deficits during winter and early spring in analogy with many other regions around the world. Two commercial cultivars, commonly used by farmers, with different time to flowering (LF: late flowering; EF: early flowering), under three initial soil water conditions (well-watered, moderately-watered and dry conditions) at three sowing dates were simulated with CERES-WHEAT for a series of 39 years. Wheat yield was higher for the LF than the EF cultivar under average (LF = 5437 vs. EF=5112 kg ha−1) and no-water restriction years (LF = 7915 vs. EF=6956 kg ha−1), while the opposite was observed in dry years (EF = 4128 vs. LF=3255 kg ha−1). Reductions in grain yield were associated with reductions in grain number, mainly explained by a lower partitioning to reproductive organs, principally limited by water shortage. The LF cultivar used more water than the EF cultivar before anthesis depleting soil water reserves (p < 0.05) and losing the yield potential advantage in dry years. Genotypic differences were more evident under initial soil well-watered conditions (16 %) compared to moderately-watered (13 %) or dry conditions (9%). Therefore, cultivar selection could partially compensate the deleterious impacts of water deficit on wheat yield under early water stress pattern environments. These results highlight the relevance of design management practices under variable water scenarios in order to reduce yield gaps.