Evaluation of water supply for olive trees through rainwater harvesting in semi-arid regions in Kohgiloyeh va Boyerahmad Province

Abstract Lack of stored soil moisture is an essential factor in intensification of the problems of arid and semi-arid areas in Kohgiloyeh va Boyerahmad Province. In these areas, limited surface water and groundwater have rendered vast areas of the region’s fertile lands useless. Despite these problems, appropriate conditions can be provided to plant resistant and adapted species such as olive through increasing moisture durability in the soil profile and optimizing precipitation. The aim of this research is to evaluate water supply for olive trees through rainwater harvesting and select the most appropriate method of increasing moisture durability in the soil profile in a semi-arid area of Kohgiloyeh va Boyerahmad province. Rhombic insulation systems on steep lands were used for fast collection of rainwater; gravel filters were installed to reduce evaporation and facilitate the rapid transfer of collected water; and stubble, manure, peat, waste sponge, and super absorbent were employed to store water and increase moisture durability. This study was performed in randomized complete block design with five treatments including stubble, manure, peat, waste sponge and super absorbent with gravel filter and control (natural soil) treatment in 3 replication on north-facing lands with 15-20% slope. To make comparisons, plants were chosen randomly from the treatments and control with similar root systems, leaves and the number of branches. The system for the precipitation harvesting was rhombus-shaped (dimensions 2×2) with nylon insulation. This project tried to maximize precipitation utilization to meet plants’ water demand. However, when rainfall was less than the minimum water requirement for olive trees, supplementary irrigation was provided based on the minimum water requirement.