Effect of Deficit Irrigation and Partial Root - Zone Drying on Yield and Water Use Efficiency of Two Potato Cultivars

Potato is one of the main products of agriculture in feeding the world's population and agricultural economy. The production of potato in the world occupies the forth place after wheat, rice and corn. In Iran, annual production of more than 5.5 million tons potato, has made this crop the most important food after wheat. On the other hand, in arid and semi-arid regions, water is the most important limiting factor for production of agricultural crops such as potato. Considering the water use efficiency is one of the most effective ways to deal with the water crisis and increasing the quality and quantity of agricultural productions. Production increasing per unit of water consumed (increasing water productivity) by improving the selection of plant varieties, irrigation management and use of new irrigation methods may be feasible.
Material and The research was performed in the Chahartakhteh research station (32° 18' N. and 50° 55' E.) with 2090 m height above sea level and semi-humid climate with moderate summers and cold winters. Average annual rainfall is about 320 mm mostly during winter. The soil moisture and temperature regimes are Typic Xeric and Mesic, respectively. Soil texture is silty clay.
In order to determine the best method of deficit irrigation for optimizing water use efficiency and yield of two potato cultivars, an experiment was performed in Agricultural and Natural Resources Research Center of Chaharmahal va Bakhtiari farm in 2013. The experiment was based on randomized completely blocks with split - split plot design in three replications. The furrow and tape drip irrigation methods were as the main plots, two potato cultivars as sub plot units and four deficit irrigation managements as the secondary sub plot units including CI(100%), RDI80(80%), RDI65(65%) of available water depletion (AWD) and partial root-zone drying (PRD) during full growth period.
Almera and Burren cultivars are two new cultivars of high yield and quality of early growth period of approximately 90-80 days, high compatibility with Chaharmahal va Bakhtiari climate and more regions of Iran.
Analysis of variance (ANOVA) of studied factors showed that the deficit irrigation management on tuber yield (ton/ha), tuber yield per plant, the amount of starch, soluble sugar, proline, chlorophyll, water use efficiency, and water productivity were significant (P≤0.01). Effects of cultivar on tuber total yield, tuber yield per plant, soluble sugar, water use efficiency, and water productivity were significant (P≤0.01). The interaction between cultivar and deficit irrigation management was only significant (P≤0.05) on tuber yield (ton/ha), proline, water use efficiency and water productivity.
The results showed that Burren cultivar in comparison with Almera was better in tuber yield (19%), water productivity (20%), water use efficiency (19%), and resistance of draught in all deficit irrigation treatments. Maximum tuber yield (59.02 ton/ha) was obtained in Burren cultivar under complete irrigation. Minimum tuber yield (23.1 ton/ha) was obtained in Almera cultivar under deficit irrigation management RDI65 (65% of available water depletion). The maximum water use efficiency (16.79 Kg/m3) and water productivity (14.78 Kg/m3) were obtained under tape irrigation and partial root-zone drying (PRD) treatment. The minimum water use efficiency (7.46 Kg/m3) and water productivity (4.81 Kg/m3) were obtained under furrow irrigation and deficit irrigation management RDI65.
Effect of cultivar was not significant on amount of irrigation water during the growing season. The amount of irrigation water for two cultivars was the same and 4711 m3.ha-1. The amount of irrigation water in the different deficit irrigation managements showed that the highest water use was in CI (5615 m3 ha-1) and lowest water use was in deficit irrigation management RDI65 (4065 m3 ha-1) treatments.
Deficit irrigation management RDI80 ¡PRD and RDI65 in comparison with CI led to reduction of irrigation water amount 16, 21 and 28% of irrigation water amount.
Due to the results of this study, the high consumption of water in agriculture, for optimal use of available water resources, the methods with high water use efficiency and productivity, such as tape irrigation, the PRD irrigation management and the use of drought resistant cultivars is recommended. According to the limitation of water resources, for optimizing water use, the best suggestion for reducing water use on potato, is using Burren cultivar with suitable quality and high yield potential, and deficit irrigation management (PRD).