Estimation of the Water Uptake in Olive Trees(Olea Europae) based on Runoff Harvesting System During Dry Period in Negev Desert, Israel
This paper presents a study of a field trial experiment at olive orchard irrigated by runoff harvesting system under a dry climate which was carried out on 5-year-old olive trees (Olea europaea. L, cv. Barnea) in the middle of Negev desert, Israel, starting right after the floods, onwards during the summer growing season. The beginning of the experiment occurred after 2 years with little rain and no run-off events. The olive trees were under severe drought stress when we first initiated a controlled flooding in 2017. In the second research year (2018), a massive natural flood had occurred at the end of April. Results show that the water distribution within the soil was highly inhomogeneous even under flood conditions. Soil water loss rate, due to transpiration was mainly correlated with the total amount of soil water and not atmospheric conditions. The physiological activities (photosynthetic and transpiration rates and stomatal conductance) significantly increased under the wet condition and gradually decreased during the prolonged dry period. Root distribution in soil was spatially non-homogeneous within plots and among plots. The root system responded in such a way that it spread its root system preferentially to areas with higher soil water content. Specifically, roots initially uptake water from shallow soil layers (0.3-1.5m) then shifted to the deeper layers (3-4 m). The results of all these measurements were combined and compared to see how olive trees respond to drought stress and recovery after watering and to obtain the transpiration rate of olive trees under a range of water availability conditions.
Keywords - Tree; drought and re-watering; soil water balance; irrigation; root; neutron probe