Soil hydraulic properties and pore dynamics under different tillage and irrigated crop sequences

Soil hydraulic properties and pore continuity are important parameters of soil quality and may differ among tillage systems, crop rotations, and change over time. However, there are some contrasting results, depending on soil type, climate and cultivation history on the spatial and temporal variations. The objective of this study was to determine spatio-temporal dynamics of soil hydraulic properties and pore characteristics (i.e., pore volume, effective porosity, and continuity) on a silt loam long-term tillage field experiment, in Agramunt, NE Spain, during two cropping years. Undisturbed soil samples were used to determine soil water retention, θ(Ψ), and soil hydraulic conductivity, K(Ψ), curves in two different tillage systems (intensive tillage, IT vs no-tillage, NT), two crop sequences (short fallow-maize, FM vs legume-maize, LM) and two positions (within the row of crops, W-row vs between the rows of crops, B-row). The results revealed that LM had greater specific hydraulic conductivity, K_pc in its macroporosity (>1000 µm) than FM due to greater number of effective pores, N_pc and effective porosity, ε_pc. Soil water content, θ was greater under IT than under NT at higher soil water matric potential, Ψ (≥-3 cm H₂O), whilst the opposite was observed at lower Ψ (≤ − 50 cm H₂O). Long-term NT showed greater hydraulic conductivity, K at higher Ψ (≥ − 10 cm H₂O) than IT, and no difference at lower Ψ. Although IT had greater pore volume, ϕ_pc than NT in the macroporosity and coarse mesoporosity (1000–60 µm) pore size classes, NT had two times greater K_pc than IT due to increased N_pc, ε_pc, and pore continuity, C_wpc. K(Ψ) and pore characteristics showed spatial variations (W-row vs B-row). W-row had significantly greater K at higher Ψ (≥ − 3 cm H₂O) than B-row. Temporal dynamics of soil hydraulic properties and pore characteristics were not evident under IT during crop succession. This study shows that LM increases specific hydraulic conductivity of soil macroporosity by increasing the number of effective macropores and the effective porosity. In a Mediterranean climate, this may improve the hydrological functions of agricultural soil and associated crop yield. Further, long-term NT formed a stable number of effective macropores and coarse mesopores, and showed a greater pore continuity in coarse and fine mesopores, resulting in improved soil water flux.