Plant-available soil water capacity: estimation methods and implications

Abstract

SUMMARYThe plant-available water capacity of the soil is defined as the water content between field capacity and wilting point, and has wide practical application in planning the land use. In a representative profile of the Cerrado Oxisol, methods for estimating the wilting point were studied and compared, using a WP4-T psychrometer and Richards chamber for undisturbed and disturbed samples. In addition, the field capacity was estimated by the water content at 6, 10, 33 kPa and by the inflection point of the water retention curve, calculated by the van Genuchten and cubic polynomial models. We found that the field capacity moisture determined at the inflection point was higher than by the other methods, and that even at the inflection point the estimates differed, according to the model used. By the WP4-T psychrometer, the water content was significantly lower found the estimate of the permanent wilting point. We concluded that the estimation of the available water holding capacity is markedly influenced by the estimation methods, which has to be taken into consideration because of the practical importance of this parameter.Index terms: field capacity, permanent wilting point, soil water retention curve modeling, Oxisol, land use planning.( RESUMO: CAPACIDADE DE ÁGUA DISPONÍVEL NO SOLO PARA AS PLANTAS: MÉTODOS DE ESTIMATIVA E IMPLICAÇÕESA capacidade de água disponível no solo para as plantas é definida como o conteúdo de água entre a capacidade de campo e o ponto de murcha permanente e tem vasta aplicação prática no planejamento do uso da terra. Em um perfil de Latossolo representativo da região do Cerrado, objetivaram-se estudar e comparar métodos de estimativa para o ponto de murcha permanente, empregando os aparelhos de psicrômetro WP4-T e a câmara de Richards, utilizando amostras com e sem preservação da estrutura, bem como para a capacidade de campo, estimando-a pela umidade do solo submetido às tensões 6, 10 e 33 kPa, e pelo ponto de inflexão da curva de retenção de água calculado nos modelos de van Genuchten e polinomial cúbico. Verificou-se que para o Latossolo em estudo a capacidade de campo determinada no ponto de inflexão apresenta maior valor de umidade em comparação aos demais métodos e que mesmo nesse ponto são encontradas diferenças na estimativa em razão do modelo utilizado. Pelo psicrômetro WP4-T, valores significativamente menores de umidade foram encontrados para a estimativa do ponto de murcha permanente. Concluiu-se que a capacidade de água disponível foi influenciada marcantemente pelo método utilizado na estimativa da capacidade de campo e do ponto de murcha permanente, o que precisa ser considerado em virtude da importância prática desse parâmetro.Termos de indexação: capacidade de campo, ponto de murcha permanente, modelagem da curva de retenção de água do solo, Latossolo, planejamento de uso terra.

Critical soil moisture range for a coffee crop in an oxidic latosol as affected by soil management

“…For instance, when a conventional management system that uses shallow furrows and where the soil is superficially chemically amended, the root system stays shallow in the first 2 years. Growth is limited in the short drought periods in the rainy season because the soil has very little available water in this part of the profile within a few days after rainfall (Santos et al, 2014;Serafim et al, 2013a;Silva, 2012;Silva et al, 2014). Considering that water stress can reduce the productive potential of the coffee crop by up to 80% (DaMatta and Ramalho, 2006), it is necessary to use strategies to improve the physical attributes of the soil profile and promote rooting to greater depths.…”

Root spatial distribution in coffee plants of different ages under conservation management system

“…After reaching equilibrium at the matric potential of -6 kPa (considered as the field capacity for Latosols -Oxisols) (Ferreira and Marcos, 1983;Silva et al, 2014), some samples were weighted and used to determine the soil resistance to penetration (RP), by using a bench top electronic penetrograph (Tormena et al, 1998;Lima et al, 2012).…”

“…During soil structural organization, there are alterations in pore distribution and configuration, which interfere with root system distribution and plant growth (Carducci et al, , 2014a(Carducci et al, , b, 2016Silva et al, 2014).…”

“…Based on this premise, some coffee growers in Minas Gerais have adopted a soil management system which consists of periodically mowed grass cultivation (Brachiaria decumbens) between planting rows as a permanent source of organic matter, associated with the building of fertility in deep soil layers, which is possible due to the adoption of a deep, fertilized planting furrow and to the gypsum application on soil surface. This management improves physical and chemical soil conditions, as well as increases root system depth (van Raij, 2008;Serafim et al, 2013a, b, c;Silva, 2012;Carducci et al, 2014b;Silva et al, 2014).…”

Synthetic Polymers on Water Retention and Pore Distribuition in a Clayey Latosol

“…Whereas Latosol has low retention capacity of plant extractable water and that such soils cover large expanses of the Cerrado region SILVA et al, 2014) which is characterized by the occurrence of prolonged periods of drought (CARDUCCI et al, 2015), the study of practices that prioritize water saving is fundamental.…”