Applied water status and water productivity in pistachio orchards of Damghan region at on-farm conditions

Pistachio cultivation is important because of its considerable area under cultivation in Damghan region and its share in the economy of the region and the province. Due to the amount of irrigation water required and limited access to water in the region and the unusual conditions of water and soil in the region, it is necessary to manage water consumption and optimize it. Improving irrigation systems in pistachio orchards, while reducing demand and saving water consumption, allows for better distribution of available water. If the current conditions continue and with an increase in groundwater levels, an increase in the negative balance of the aquifer and a decrease in water quality will cause many problems. This study was conducted to determine pistachio water consumption, status of water productivity index and also to compare irrigation systems in Damghan pistachio orchards.

For sampling, 148 samples were randomly selected from among the orchards of farmers in different areas of Damghan region, some of which lacked technical conditions and reliable data. Therefore, research data was collected by random sampling method and also through questionnaire data and interviews with operators or farm managers of 112 pistachio orchards. In this study, 112 gardens in Damghan region were selected and studied in terms of water use and water productivity. The amount of water consumption, yield and water productivity of selected pistachio orchards in Damghan region were determined. Damghan Pistachio Research Station is located at 54o20′8″ east longitude and 36o9′48″ north latitude and the altitude is 1130 meters above sea level. In agriculture, the physical productivity of water is generally used. The physical productivity index of irrigation water was obtained from the ratio of crop yield under each of the treatments to irrigation water. Three systems of surface irrigation, surface drip irrigation and subsurface drip irrigation were evaluated in 7 selected gardens.

The average yield of trees over 20 years of selected orchards was 4950 kg.ha-1 and the average yield of trees over 10 years of selected orchards was 3088 kg.ha-1. The average water consumption in surface irrigation method in the gardens of exploiters was estimated to be more than 8380 m3.ha-1, which is less than the water requirement documents. The amount of water used in drip irrigation is 8000-5000 m3.ha-1 and in subsurface drip irrigation is 4927 m3.ha-1, which is less than the national document. The water productivity index in each of these systems (surface irrigation, surface drip irrigation and subsurface drip irrigation) were 0.6-0.5, 1.5-2.5 and 0.406 kg.m-3, respectively. Water productivity index in trees over 20 years of selected orchards was equal to 0.54 kg.m-3 and in trees over 10 years old was equal to 0.349 kg.m-3. 53% of orchards have water productivity of less than 0.20 kg.m-3. Water productivity in surface irrigation, drip irrigation and subsurface drip irrigation systems were 0.5-0.6, 0.25-0.15 and 0.406 kg.m-3, respectively. Obviously, the relative advantage of irrigation methods for pistachio orchards depends on water quality and soil characteristics, water availability, tree age and garden management.

In analyzing the productivity index and yield of pistachio orchards, in addition to garden management, other factors such as tree age, cultivar type, water and soil quality, soil characteristics, alignment of climatic data and plant nutrition, process and ease of nutrient uptake and ..... also be noted. But this does not mean the advantage of drip or subsurface irrigation over surface irrigation. The range of water – yield relationship and analysis of the water productivity index indicate the existence of a yield and water productivity gaps in Damghan pistachio orchards. By choosing the best models and providing additional technical recommendations in the form of promotional training, he solved the existing gaps. Acknowledgement The valuable assistance of Agricultural Engineering Research Institute, Semnan Agricultural Jihad Organization, Damghan Agricultural Jihad Management and colleagues of Damghan Pistachio Research Station in carrying out related research are gratefully acknowledged.