Spatial and temporal variation in drought types for wheat in Argentina and its association with actual yield and fertilization rate

Abstract

Wheat annual acreage in Argentina is 3.0–6.8 Mha and spans across latitudes between − 24° to − 38° in regions with diverse climate, soil, and management practices. Identifying regional limitations is critical for both breeding and crop management. The objectives of this work were to (1) determine the environment types of rainfed wheat in Argentina as sets of spatial, probabilistic patterns of water stress across the region, accounting for crop phenology, soil depth and plant available water at sowing, and (2) associate the environment types with actual yield and fertilizer rate in farmers’ fields. Water stress was quantified as the simulated daily ratio between actual and potential crop transpiration (WSI) using the CERES-Wheat model and climate series (1983–2015) in 15 locations and classified the WSI trajectories along crop phenology into environment types. Environment types revealed two contrasting regions, one in the southwest and east, and the other in the center and north of the country. The southwestern-eastern region showed a higher synchrony between rainfall and crop cycle, higher frequency of non-stressful environments, higher actual yield and higher fertilization rates in farmers’ fields. The central-northern region showed lower synchrony between rainfall and crop cycle, a higher frequency of stressful environments, lower actual yield, and lower fertilization rates. This work highlights (i) the diverse environmental conditions for wheat in Argentina, hence providing a quantitative framework for matching adaptive traits and crop management to specific environments, and (ii) the two causal links between drought and crop yield reduction: a direct biological link whereby dry soil and elevated evaporative demand reduce growth and yield, and an indirect link mediated by a more conservative cropping approach with lower inputs in drier, riskier environments.