Stability and patterns of topsoil water content in rainfed vineyards, olive groves, and cereal fields under different soil and tillage conditions

Topsoil water content (TSWC) varies at spatial and temporal scales owing to the influence of several factors. In woody crops, few studies have analysed these dynamics under rainfed conditions. The temporal stability of the spatial patterns of TSWC in a Mediterranean rainfed sub-catchment (27 ha; Spain) was analysed during 12 months. Cropland includes four vineyards with cover crops, five cereal fields (fallow/crop rotation), one olive grove under conventional tillage, and one abandoned olive grove. In total, nine land use compartments were distinguished in twelve fields and nine non-cultivated soils. During the test period (May 2016 April 2017) the monthly TSWC values (mean 13.1% vol. 8.0) showed a significant correlation with evapotranspiration. The spatial variability of TSWC increased under dry conditions and more homogeneous patterns appeared in the wet surveys. The vineyards' inter-rows had the wettest (62% > in the rows) conditions owing to the cover crops and their high soil-water holding capacity, and average temporal stability. The vineyards' rows were dry and very stable due to the tillage practices (higher elevation) and the low infiltration rates; and the corridors had wet and stable conditions. The forest presented the driest and stable temporal conditions associated to the water demand by the trees. Soil in the fallow cereal fields was drier and more stable than in the cereal fields. The abandoned olive grove showed wetter though less stable conditions than the olive grove. The trails had wet but not stable conditions. The different land uses and tillage practices influenced more the TSWC dynamics than the spatial variability of the analysed soil physical properties. However, silty loam and loamy soils presented wetter and more stable conditions than the average values, and the sandy loam and loamy sand soils had drier and less stable conditions.