Assessment of Effect of deficit irrigation under surface and subsurface irrigation conditions on vegetative development and yield of Citrus

Due to the severe water deficit in recent years, and according to agricultural sector policies, drip irrigation has been carried out in most plants of Iran. Subsurface irrigation and deficit irrigation were not studied. In arid and semiarid regions where water resources are scarce, in order to Protection of soil and water resources, irrigation water use efficiency and soil salinity is an important issue. In order to evaluate and resolve drip irrigation system problems, water management in the field, subsurface irrigation and deficit irrigation a lot of research has not been done in South Kerman. Although surface drip irrigation is an efficient irrigation method, it has had relatively limited expansion due to several disadvantages such as soil surface evaporation and lose of water. Recently, subsurface irrigation method that is able to avoid most of the aforementioned drawbacks has been introduced in the world. Due to high sunlight and high soil surface evaporation in many regions of Iran, subsurface irrigation can be very useful in decreasing evaporation. On the other hand, by applying regulated deficit irrigation, it can be optimized by improving the quality of the product and Saving Water. The objective of this work is to assess the performance of subsurface irrigation and to compare it to a surface drip irrigation system. In this study, which was carried out at the Research Station of South Kerman Agricultural and Natural Resources Research and Education Center during 2015-2016, the effect of different deficit irrigation methods (Irrigation with 80%, 60-100% and 100% water requirement) under three methods of surface drip irrigation, subsurface drip irrigation and Deep subsurface irrigation were investigated on vegetative development(length of the main branch, length of the sub branches, Number of buds, Trunk diameter, Tree height and Canopy volume) and yield of citrus (oranges). The results showed that deficit irrigation with 80% water requirement under deep subsurface irrigation, in addition to 33.65% water saving, was not significantly different in terms of vegetative characteristics and yield compared to full irrigation under surface drip irrigation. However, deficit irrigation under surface drip irrigation due to higher losses of water causes the plant to withstand and reduce the yield of the product. Intermittent deficit irrigation with 60-100% water requirement had better vegetative characteristics and weaker yields than uniform deficit irrigation with 80% water requirement. deep subsurface irrigation showed the best performance by preventing water evaporation and proper distribution of moisture in the root zone with 20% more canopy volume and 28% higher yield than the other two methods of irrigation.