How does soil water retention change over time? A three-year field study under several production systems

Abstract

Agricultural practices and meteorological conditions affect soil structure and soil hydraulic properties. However, their temporal evolution is rarely studied, and even less in the field. Thus, their dynamics are rarely taken into account in models, often leading to inconsistent results and poor decision making. In this study, the temporal evolution of water retention properties and soil structure was monitored over a 3-year period under several contrasting production systems. Soil Water Retention Curves (SWRCs) obtained directly in the field (with soil water content and potential sensors) were compared with theoretical SWRCs predicted by pedotransfer functions (PTFs) and laboratory SWRCs measured on undisturbed samples. Bulk densities were measured every 2 months. Results indicate a high degree of variability in SWRCs over time and between production systems. The results suggest that variations in the soil water retention behaviour can be induced by crop differentiation, weed control, crop residue management, compaction during harvest, or the introduction of temporary grassland. Contrasting climatic conditions between 2021 (water excess), 2022 (severe drought) and 2023 (intermediate) provided a unique opportunity to study the resilience of the crop systems to extreme climatic conditions. Different soil drying dynamics were observed and some agricultural practices were identified as influencing the soil water retention behaviour for at least 2 years. Comparison of SWRCs showed that the theoretical curves obtained from PTFs are not a good representation of the field SWRCs, especially for less conventional agricultural practices. The laboratory curves are closer with similar trends. However, these SWRCs are not optimal for investigating the temporal evolution of water retention properties. This research also shows that agricultural practices and crops can be levers for contributing to greater food resilience against future climatic conditions. Therefore, to assess the relevance of production systems for tomorrow's needs, studies should focus on the impact of multi-cropping systems on water retention dynamics in the field.