Plant available water in Brazilian soils: assessment of its lower limit by a process-based transpiration reduction function

• Grant number: 24/13218-9
• Support Opportunities: Regular Research Grants
• Start date: May 01, 2025
• End date: April 30, 2028
• Field of knowledge: Agronomical Sciences - Agronomy - Soil Science
• Principal Investigator: Quirijn de Jong van Lier
• Grantee: Quirijn de Jong van Lier
• Host Institution: Centro de Energia Nuclear na Agricultura (CENA). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Associated researchers: Fabio Ricardo Marin

Abstract

The amount of water available to plants is used agronomically as an indicator of soil suitability for crop growth and biomass production, as well as in project design and irrigation management. Ecologically it is used to understand the hydrological functioning and spatial distribution of plant species in ecosystems. Traditionally, total available water (TAW) is defined as the difference between water content at field capacity (FC) and wilting point (WP) whose values are very often taken to correspond to a given value of matric potential. Readily available water (RAW) is a fraction of TAW defined as the water content between FC and the limiting point (LP). Although the challenge in determining TAW and RAW lies in the correct determination of FC, LP, and WP, their values are very often taken as if they would correspond to a certain value of matrix potential. A proposal for an estimate of TAW and RAW based on the physics of the drainage process and water extraction by the root system was recently developed and tested by the research group proposing this project and called "Flux-based method" (FBM). For the lower limits WP and LP, the method is based on the MFLUX root water uptake model, which predicts the extraction of water from the soil by the root system depending on the hydraulic properties of the soil and plant, and atmospheric conditions. This project aims to calibrate the MFLUX model for a soybean scenario in the State of São Paulo. The comparison with experimental data will allow us to improve the prediction of the respective lower limits LP and WP by FBM. We intend to contribute scientifically to research in soil physics in the subarea of soil-plant-atmosphere transfer processes, especially with advances in understanding plant water availability as a function of the soil and plant hydraulic properties. The generated knowledge will be applied to soils from the Brazilian soil database HYBRAS, allowing a reassessment of TAW in Brazilian soils. (AU)