Application of porous clay capsule technique in optimizing water consumption of citrus orchard

Introduction
Water is one of the main important environmental factors limiting plant culture, in arid and semiarid regions like Iran. Providing continuous soil moisture content in the range of field capacity and reducing water losses in near root zone can play a key role in the development of soil and water management programs. Subsurface irrigation system with porous clay capsules are able to release water in the soil at field capacity range. This method is one of the traditional methods to reduce water consumption and increase water use effficiency for providing water requirement of plants in small scale farms at the worlds. There are different types of porous pipes. Clay nozzles are a type of porous clay pipes that allow optimal use of irrigation water due to the moisture supply of field capacity at the roots of plants.
Materials and Methods
In this study, subsurface irrigation with porous clay capsule nuzzle was used to provide the water  requirement of two fruitful plant (Grapes and Oranges) and measure the volume of water consumption in comparison with drip irrigation method. Porous clay capsule is able to release water into soil about field capacity in low hydroustatic pressure. The soil water content in field capacity was measured by mini soil Tensiometer in 30 kPa soil suction. Soil moisture in field capacity content was 28% for clay soil texture in citrus orchard. In subsurface and surface irrigation methods, 4 porous clay capsules and 2 dripper (8 litr.h^-1), were placed for each citrus plant respectively. The volume of water consumed after each irrigation in both methods was measured by a water meter counter with precision +/-1 liter. In citrus plants, to compare the effect of irrigation type the collar diameter and plant height were studied for three consecutive years, and were compared using t-test (P<0.05).
Results and Discussion
The volume of water used in subsurface irrigation method was less than the surface irrigation method. The results showed that the water supply using buried porous clay capsule irrigation method for citrus plant compared to surface drip irrigation method was associated 42% reduction in water consumption.. Comparison of collar diameter and plant height of citrus plants showed that there was no statistically significant difference (p<0.05) in two irrigation methods. Collar diameter and height growth of citrus trees in subsurface and surface irrigation methods in 2015 compared to 2012 was about 2.5 times.
Conclusion
According to the results of the present study, it can be concluded that the use of porous clay capsules will be one of the most effective traditional methods of optimization and management in water consumption of small scale orchards, especially at arid and semiarid region. An examination of the work done to date on clay nozzles shows that less attention has been paid to the economic aspects and competitiveness of these parts with other nozzles available in the market. It seems that the challenge of sedimentation of water-soluble materials inside the parts or attacking the roots on them has prevented the entry of large private sector investors into this completely economic and high-income environment.