Understanding the water flow and storage processes in the soil allows planning, managing, and optimizing the use of water resources in the soil-plant-atmosphere system. The so-called agro-hydrological models are used to predict and simulate components of water balance and crop yield. These models also allow simulating scenarios by adopting different soil management strategies under different environmental and climatic conditions. The agro-hydrological model SWAP has been used worldwide, because it carries out both water balance through vertical water flows, as long-term field scale simulations. However, the model SWAP has a high demand for input variables, including the hydraulic properties of soil water retention (SWR) and soil hydraulic conductivity (SHC). Measurements of these properties are difficult and costly, which ends up making their determination onerous at large scale. Pedotransfer functions (PTFs) are an alternative for estimating SWR and SHC from texture, density and other data available. The aim of this research is to (i) estimate SWR and SHC by pedotransfer functions that use physical (PTF_Splintex 2.0) and empirical (PTF_Dasam) principles developed for soils in the Northeastern Brazil, and (ii) test and evaluate the use of these hydraulic properties estimated in the components of the water balance and in the agricultural yield predicted by the agro-hydrological model SWAP. This functional analysis will be evaluated by the performance of the model by comparing its estimates of agricultural productivity with values observed in different soils in Northeastern Brazil. We expected this research will contribute to the dissemination of (i) pedotransfer functions in estimating the hydraulic properties of soils in tropical regions and (ii) their viability in the agro-hydrological model SWAP.
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