Calibração de sondas capacitivas, funções físico-hídricas e variação do armazenamento de água em um argissolo cultivado com palma forrageira

Abstract

Objetivou-se, com este trabalho, realizar a calibração de três sondas capacitivas, visando a utilizá-las na definição de funções físico-hídricas e na análise da variação espacial e temporal do conteúdo (q) e do armazenamento de água, em um Argissolo Vermelho-Amarelo, cultivado com três clones de palma forrageira, no Semiárido pernambucano. O estudo foi executado numa área experimental situada em Serra Talhada, PE. Para isso, foi realizada a calibração de três sondas capacitivas, usando-se dados de densidade aparente do solo, de umidade gravimétrica e de frequências relativas, em cinco condições de umidade do solo. Aplicou-se o método do perfil instantâneo, para determinação do fluxo vertical de água, e do potencial matricial de água no solo. Em seguida, analisou-se a variação espaço-temporal do q e do armazenamento de água no solo. As medidas de frequência relativa das sondas capacitivas apresentaram elevada relação com os dados de q (R2 > 0,87). A partir do método do perfil instantâneo, foi possível determinar as funções da condutividade hidráulica e do potencial total de água no solo, em relação ao q, com elevados coeficientes de determinação (R2 > 0,91). Não houve diferenças significativas do q entre os clones de palma forrageira.

Soil water dynamics and evapotranspiration of forage cactus clones under rainfed conditions

“…However, differences between DD/CR, ΔA, and ET ac were verified for some periods over time, depending on rainfall regime ( in areas cultivated with some Opuntia spp., as the root system can reach greater depths, forming channels in the soil that promote water movement, as found by Snyman (2006a). Despite the high cumulative values of rainfall during some periods (1, 2, and 9), drainage was low, because, after dry periods, most of the water is used in soil replenishment or is extracted by the plant root system, as described by Primo et al (2015). This can be explained by the high capacity of cacti to store water in cladodes and by the elongation of the root system, which increases rapidly after being subjected to long periods of drought (Snyman, 2006a(Snyman, , 2006b).…”

Hydrodynamic changes of the soil-cactus interface, effective actual evapotranspiration and its water efficiency under irrigation

“…Silva et al (2015b) also did not find differences between these clones. The ΔS is highly dependent on the applied amount of water, atmospheric demand, soil characteristics and water uptake capacity of the forage cactus roots (Primo et al, 2015).…”

“…These frequencies were defined based on information of forage cactus areas in Rio Grande do Norte, which received irrigation depths of 5.0 mm every 14 days, through a pressurized drip system. (Primo et al, 2015). These measurements started on June 1, 2012.…”

“…Q z through capillary rise or deep drainage was estimated using the equation of Darcy-Buckingham equation (Silva et al, 2014a), which requires the soil hydraulic conductivity and total water potential (mm), obtained through the application of the instantaneous profile method (Primo et al, 2015).…”

Meteorological variables and morphological characteristics influencing the evapotranspiration of forage cactus

“…The water content was monitored over time, using a capacitive sensor (Diviner 2000®, Sentek Pty Ltda., Australia) and access pipes installed, in each sub-subplot, up to 0.90 m of depth and 0.10 m from the rows of the species. The sensor was calibrated locally according to Araújo Primo et al (2015), and monitoring was done every two days. Soil water balance was accounted at 14-day intervals.…”