Hydrostatic Equilibrium between Soil Samples and Pressure Plates Used in Soil Water Retention Determination: Consequences of a Questionable Assumption

Autor(es)

van Lier, Quirijn de Jong ^[1] ; Rodrigues Pinheiro, Everton Alves ^[1] ; Inforsato, Leonardo ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Ctr Energia Nucl Agr, Piracicaba, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Revista Brasileira de Ciência do Solo; v. 43, 2019.
• Citações Web of Science: 0

Resumo

ABSTRACT Soil water retention is among the soil hydraulic properties most routinely measured in studies of soil physics and related areas. This property is used in dynamic simulations of vadose zone processes such as soil water availability, surface boundary processes of evaporation and infiltration, and the fate of soil pollutants. The most common measurement technique consists in establishing a hydrostatic equilibrium between an initially saturated soil sample and a porous medium at a certain tension on a tension table or pressure plate. However, there is reasonable doubt about the assumed hydrostatic equilibrium, especially in the dry range at low pressure heads. In this study we compared the traditional pressure plate apparatus protocol to an inverse parameter estimation protocol based on a transient evaporation experiment. Independent pressure head measurements using a dewpoint device were also performed. We sampled a variety of soil textures typical of the Brazilian subtropical humid zones, aiming to show differences between textures in their subjection to hydraulic nonequilibrium. The performed experiments allow to conclude that the two compared protocols showed real pressure heads in samples on a pressure plate to be less negative than the assumed ones, leading to an overestimation of the soil water content in the dry range at low pressure heads, especially in fine-textured soil samples. This affects the reliability of most soil hydraulic databases, derived PTFs in the dry range, as well as the wilting point estimation. Water availability predictions based on total and readily available water are more sensitive to the water retention measurement method when the chosen lower limits of available water are closer to the wilting point. In this sense, irrigation timing criteria based on readily available water should be preferred over total available water, especially for fine-textured soils. Finally, given the low reliability of the pressure plate apparatus for low pressure heads, possibly biasing hydrological simulations and their interpretation, alternative measurement methods for the drier part of the soil water retention curve should be preferred, e.g., the proposed inverse modeling of evaporation experiments. (AU)

• Processo FAPESP: 17/17793-4 - Relação das propriedades hidráulicas do solo com planta e clima na avaliação da adequação do solo à produtividade agrícola sob sequeiro e irrigação
• Beneficiário: Everton Alves Rodrigues Pinheiro
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Pós-Doutorado
• Processo FAPESP: 16/16128-4 - Função hidráulica do solo no fornecimento de água às plantas: uma abordagem física em escala de agroecossistema
• Beneficiário: Everton Alves Rodrigues Pinheiro
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado