Adaptation strategies to address irrigation demand in the Mediterranean under climate change

Irrigation in the Mediterranean region consumes at least 80% of the total water consumption. This is expected to increase due to the impacts of climate change. There is a lack of data regarding the irrigation needs of agricultural plants especially in the Mediterranean region.  To address this issue, the Water Use Efficiency of an Avocado plantation in Crete, Greece is being assessed in systematic way in order to minimize the environmental footprint and impact of the operation while maximizing the benefits for the farmer and the environment. A hydrologic and plant monitoring station have been established in an avocado plantation to determine optimal irrigation schemes, the water use efficiency of the trees and ways to improve plant productivity. The station consists of a precipitation and meteorological station, soil moisture profilers near and away from the tree, irrigation flow monitoring, NDVI and PRI cameras for the estimation of the above ground biomass changes.  These data that are collected every 15 minutes, together with expert knowledge were used to determine optimal irrigation schemes such as deficit irrigation that will conserve the use of water as well as maximize plant production.  The plants were irrigated the amount estimated by their evapotranspiration needs.  In addition, drip irrigation was not applied in a linear fashion in the field, but in a circle with one-meter diameter from the root of the tree.  In this way, the amount of irrigation used was only 30% of the typically prescribed irrigation needs for the plants on an areal basis. Irrigation was applied every 3-4 days based on soil moisture changes in a constant fashion.  It has been observed the over-irrigation stresses the plant. Biomass production was monitored with the NDVI and PRI cameras in order to estimate the above ground production as well as to identify the conditions that plants were stressed. No tilling was practiced in order not to disturb the formation of water stable aggregates and thus the productivity of the soil. Finally, soil organic matter was added by cutting the grass grown in between the trees and leaving the clippings on site and also by not removing the leaves from the avocado. The addition of organic matter in the soil promotes the below ground biodiversity as well as the productivity of the plants and it improves the soil water retention capacity. The results of this study illustrate that we can reduce the amount of irrigation significantly (60-70% of suggested irrigation annual rates) by both increasing the soil organic matter and by irrigating the tree and not the field. Reducing irrigation rates as well increasing the soil water retention capacity can be the two main adaptation strategies that can address effectively the increases or irrigation demand due to climate change.