During the seasons 2003/04, 2004/05 and 2005/06, a study was made of the evolution of runoff as well as soil and available P and K losses in the sediment carried away in a conventional till system-that most used at the present time-and in a no till system with added pruning remains in an olive grove of the picual variety located in Torredonjimeno (Jaén, Spain). A group of microplots for sediment collection in a randomized complete block design was established. The samples were collected in the field after each storm. In the study period, a total of 21 storms were recorded, with a precipitation of 450 mm in 2003/04, 179 mm in 2004/05 and 388 mm in 2005/06. The erosivity of the rainfall was characterized and the cover percentage in the plots throughout the time was determined. The establishment of pruning remains reduced soil loss with respect to conventional tillage (CT) in the 3 years (72%). Likewise, the available P loss greatly declined in the study (46.4%) under conservation agriculture. The reduction in available K loss (72.4%) was much greater than that of available P. The close relationship between both variables and sediment production also stands out. Runoff was the parameter on which the pruning remains had the least influence with only an 11% average reduction.

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Mediterranean olive trees traditionally grow under rainfed conditions, on poor soils with steep slopes. Rainfall is mainly concentrated during autumn and winter and is characterized by intense rain pulses, separated by dry periods. The use of electromagnetic induction (EMI) techniques in these olive orchards might be questioned since EMI surveys are generally recommended to be performed under moist soil conditions. A 6.7 ha olive orchard was surveyed for EMI-based apparent electrical conductivity (ECa), both under wet and dry soil conditions. In addition, 48 soil samples were analyzed for soil texture and for soil water content (SWC) under both soil conditions. The relationships between ECa, soil texture and SWC, under both soil conditions were evaluated. Despite the significantly larger ECa values measured during the wet survey as compared to the dry survey, a similar spatial correlation structure was found, indicating temporally stable ECa patterns. Significant correlations (r) were found between both surveys for ECa (r = 0.67) and for SWC (r = 0.63). The correlation between SWC and clay content exceeded 0.60 for both surveys, and the correlation between ECa and clay content was twice as high under wet soil conditions as compared to dry soil. In both situations, the ECa surveys revealed the same patterns of soil texture, indicating that moist soil conditions are not an absolute prerequisite for the use of EMI to map the spatial variability of these soil properties. Nonetheless, measuring the ECa under different moisture conditions can provide additional information about soil moisture dynamics

Core Ideas Water retention data from saturation to oven dryness were collected for a Vertisol. New water retention and differential water capacity models were developed. Draining of intra‐aggregate pore space triggers the dry field soil moisture state. Mode of the textural pore space controls shift to wet field soil moisture state. Vertisols are well suited for rainfed agriculture in water‐limited environments as a result of their unique water transfer and retention characteristics. Despite their importance, the agro‐hydrological behavior of these soils under seasonally dry climates is not yet fully understood. We collected water retention data for a Vertisol, measured from saturation to oven dryness on 27 undisturbed topsoil (0–0.05 m) samples from an experimental field in south‐central Spain and related this information to the occurrence of field‐observed preferential soil moisture states. A continuous function was fitted to the mean gravimetric water retention data, Θ, consisting of the sum of a double exponential model and the Groenevelt and Grant model. An inflection point at pressure head |h| = 1.1 × 105 cm, Θ = 0.12 kg kg−1, and an equivalent pore radius, δ = 14 nm, was interpreted as the boundary between the clay inter‐ and intra‐aggregate pore spaces, corresponding with the transition from the intermediate to the dry field soil moisture state. The mode of the textural pore space (|h| = 7.3 × 103 cm, Θ = 0.21 kg kg−1, and δ = 200 nm) matched the transition from the wet to the intermediate field soil moisture state. We related these characteristics of the soil water retention curve with the spatiotemporal soil moisture dynamics and patterns observed in the field, characterized by fast transitions between preferential soil moisture states. The proposed framework is suitable for comparing the effects of different soil management strategies on the agro‐hydrological performance of Vertisols.

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