On-Site Recycling of Coconut Leaves as Mulch Modifies Soil Hydrothermal Dynamics in Semiarid Coconut Orchards

Abstract On-site recycling of coconut leaves as mulch modifies soil hydrothermal conditions and irrigation water use in semiarid coconut orchards. This study evaluated the effects of senescent coconut leaves ( Cocos nucifera L.) used as mulch on soil thermal and water regimes in a semiarid coconut orchard in Brazil. Five treatments were assessed, combining irrigation rates and mulch levels: bare soil under 150 and 300 L plant⁻¹ day⁻¹, and mulching with 15, 30, or 45 leaves per plant under 150 L plant⁻¹ day⁻¹. Mulching reduced diurnal soil temperature amplitude and delayed peak heating, particularly in surface layers. However, interception of irrigation water by the mulch layer was substantial, averaging 48%, 54%, and 60% for 15, 30, and 45 leaves, respectively, and was more pronounced at lower irrigation depths. Mulch also modified the spatial distribution and persistence of soil moisture. Intermediate mulch levels maintained the largest proportion of the soil profile within the optimal moisture range (0.15–0.22 cm³ cm⁻³), whereas thicker mulch layers restricted lateral wetting despite of reducing soil water depletion. Overall, soil water depletion was markedly lower under mulch (4.2 mm day⁻¹) than in bare soil (7.9 mm day⁻¹). These results indicate that coconut leaf mulch can improve soil water conservation and moderate soil temperature under semiarid conditions, although excessive mulch thickness may reduce irrigation efficiency. Optimizing mulch levels in conjunction with irrigation management is therefore essential to balance water conservation and effective soil wetting in micro-irrigated coconut systems.