Summary Field capacity (FC) is crucial for modelling soil–plant–water dynamics with bucket‐type models, supporting prevention of environmental problems (e.g. chemical leaching to deeper layers and groundwater and waste of water resources). As FC measurement in situ is labour intensive, approaches for its estimation have been proposed. However, because they differ conceptually and are based on different assumptions, the response to an application (e.g. crop yield (CY) modelling) can be rather different. This study evaluated frequently used FC approaches in scenarios quantifying differences in behaviour of soil water and air retention, evapotranspiration (ET) and CY. Also, a soil texture‐based pedotransfer function (PTF) was compared with other methods. Six sites with different soil types and management practices from tropical and temperate climates were investigated. Field capacity was estimated based on a static criterion using the water content (θ) at pressure heads (h) of 0.6, 1 and 3.3 m and at the inflection point (θi) of all water retention curves (SWRCs) and the Assouline and Or model (AO). Moreover, four equations found in the literature based on a dynamic criterion were also evaluated. For all soils, the largest FC results were obtained when θi was set as FC. The smallest FC values were obtained with θ (3.3 m) (tropical) and AO (temperate). The coefficient of variation (CV) between FC estimates, based on nine approaches, ranged from 7 to 54%. Available water storage, air capacity (AC) and ET results were sensitive to FC and showed more variation for the Brazilian sites. The PTF used estimated FC within the range of results obtained by the other nine approaches. In addition, AquaCrop was used to study the effect of FC on CY by fixing all model parameters, whereas FC was the only flexible parameter. Crop yield was sensitive to the variation in FC under low and medium rainfall, but increased with larger FC. For high rainfall, the yield was small in a scenario with large θfc because AC became yield limiting. Highlights Different approaches can be used to estimate field capacity The criteria static and dynamic and a texture-based PTF were evaluated Sensitivity analyses were performed with parameters of bucket type model and crop yield simulations Results showed that management decisions differed according to field capacity criteria

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The high demand for fuel derived from oil increases the risk of environmental hazard in agricultural fields caused by accidents with the operation of machines and spotting of fuel on the ground. When these accidents occur, a part of the spilled fuel infiltrates and redistributes in the soil according to the fuel's own physical properties. Most fuel products are light nonaqueous-phase liquids (NAPL) and contain compounds that are toxic and cause damage to the soil and to human health. The transport behavior of fuels in soils has been extensively studied but is lacking knowledge in specific soils with high clay content. This study aimed to evaluate the soil permeability (K) to the transport of water and fuels and their spatial variation in a Cambisol in southern Brazil. Furthermore, the question should be addressed whether K water may be used to estimate K fuels based on the fluid viscosities. Moreover, a spatial variance analysis should evaluate the variability between replicate repacked samples at a particular location in comparison with spatial variability caused by soil texture and bulk density differences. Results showed that K water was, on average, 4.5 times smaller than K gasoline and 1.25 times smaller than K diesel , that the correlation between measured and estimated K fuels was moderately positive for the clayey soil investigated, and that a minimum set of three repacked parallel cores for each sampling location yields a local variance that is much smaller than the semivariance at any lag distance.

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