Water harvesting techniques for improving soil water content, and morpho-physiology of pistachio trees under rainfed conditions

Water harvesting techniques have shown promising outcomes in mitigating risks, increasing yields and delivering positive influences on other ecosystems. A field study was conducted in Northern Jordan to assess the influence of combined in-situ water harvesting techniques, micro-catchment and mulching on soil moisture content, plant morphology, gas exchange [photosynthesis (Pn), transpiration (E), and stomatal conductance (gs)] and midday stem water potential (Ψsmd) of young pistachio (Pistacia vera cv. Ashori) trees. Four mulching treatments [straw, vertical gravel, horizontal gravel and control (no mulching)] and three micro-catchment areas (36, 64 and 100 m2) were used. Pistachio trees were grown under rainfed conditions for two growing seasons. Gravel mulching (vertical and horizontal) and 36 m2 micro-catchment had the highest percentage increase in plant height compared with other treatments. In addition, 36 m2 micro-catchment significantly increased gas exchange variables (Pn, gs, and E). We partially attributed that to higher soil water content and Ψsmd in the 36 m2 compared with 64 and 100 m2 micro-catchment. Interestingly, the runoff water collected from 36 m2 treatment was 75 % higher than 64 m2 (53.4 vs. 30.6 L) and 28 % higher than 100 m2 (53.4 vs. 41.7 L). Therefore, the 36 m2 is the best micro-catchment area in term of runoff efficiency. Overall, the combined water harvesting techniques, gravel mulching (vertical and horizontal) and the 36 m2 micro-catchment hold promise for improving the morphology and physiology of young pistachio trees grown under rain-fed regime.