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

Abstract

Soil management systems affect water availability to plants which is essential for perennial crops such as coffee, especially in initial years of crop establishment. The objective of this study was to investigate the effects of additional gypsum and intercropping on the least limiting water range (LLWR) in an Oxidic Latosol. We also introduced in this study a lower limit of LLWR based on crop evaporation depletion factor (p) and a critical moisture (θ*) approach. Three management systems were tested: conventional (CV-0), conservation with Brachiaria decumbens and additional gypsum [7 Mg ha−1 (G-7) and 28 Mg ha−1 (G-28)]. Three trenches (1.0 m depth) were dug for each management system for 0–0.05, 0.15–0.20 and 0.65–0.70 m depth sampling. Results showed that LLWR increases with bulk density (Bd) until a first restriction to root growth occured, due to limited aeration. LLWR was always greater than zero, indicating adequate soil quality and water stress was the main plant growth limiting factor. Adoption of θ* as LLWR lower limit allowed an average reduction of 50.2% in available water. But, this reduction was significantly greater for greater Bd, so this indicates that LLWR modeling is an aid in understanding soil management effects. At 0.15–0.20 m depth, LLWR was greater in G-28 than CV-0. Also at 0.65–0.70-m depth, LLWR in G-28 was the greatest, followed by G-7 and CV-0 treatment. G-28 showed greater LLWR than CV-0 in the interrow position. These results support the hypothesis that the use of Brachiaria in interrow and additional gypsum contributes favorably to modify the soil profile conditions for better coffee root development in conservation management systems.