Potato water requirement in different climate of Isfahan province

Potato (Solanum tuberosum L.) is an annual plant and auto tetraploid and belong to the family of Solanaceae. World production of this plant in 2014 was 385 million tons per year; about 40 percent of this amount is in Asian countries. Potato crop needs water to grow to 400 to 850 mm, although some researchers have reported the level of 900 mm. Potato crop as drought-sensitive plants may yield loss even in the partial stress of water, and the reason for this is the superficial roots and low power plants for reconstruction after water stress. Water use efficiency (sometimes also called transpiration efficiency) can be defined as the ratio of the potato tuber yield to evapotranspiration. Water use efficiency in potato-based evapotranspiration has been reported 1.9 -5.3 kg m-3. The aim of the study was to evaluate the potato crop water demand and water use efficiency in Isfahan province.
This research was carried out in different cities of Isfahan province where cultivation of potatoes was widespread in 2014-2015. According to UNESCO, where the three main criteria of classification of the water regime, type of winter and summer type are considered, 28 climate zones are present in Iran and of these; six areas include more than 90 percent of the country. Accordingly, for the cultivation of potatoes in Isfahan province, three main climatic zones can be detected. Crop evapotranspiration is influenced by weather conditions and stages of plant growth and represents the amount of water needed in a healthy plant on a farm without water restrictions. Evapotranspiration was calculated from the following equation: ET crop=∑ Kci×EToi. In the above formula Kci and Etoi were crop coefficient, and the reference evapotranspiration, respectively. Data analysis was performed with the completely randomized design for each zone, and the means were compared by Duncan's multiple range tests (at 5% level).
Analysis of data related to different cities in three climatic potatoes A-C-W, A-K-W and SA-K-W in of Isfahan province was indicated that significant differences in the rates of water and water productivity level of 1%, and water consumption in different phonological stages in 5% level. In the climate of A-C-W (including 6 cities) water requirement has a range of 4674 (Mobarakeh) to 5432 (Isfahan) cubic meters. In this climate, a range of water productivity based on three methods of drip irrigation, sprinkler irrigation, and furrow irrigation, was (4.03-5.77), (3.52-5.04), and (2.99-4.28), respectively. These numbers were in the range of values reported by other researchers (4.9-9.3 kg m-3). Water stress condition in the region is one of the reasons for high water productivity. In A-K-W climates (including 5 cities) the net water consumption per hectare was from 4609 (Natanz) to 5257 (Shahin Shahr). The SA-K-W climate (including 10 cities) the highest water requirement (6426 m3) and the lowest productivity in furrow irrigation (1.79 kg m-3) were related to Tiran and Dehaghan, respectively. On average, the water requirement of potato in three regions A-C-W, A-K-W and SA-K-W, was 5044, 5078 and 5703 m3 ha-1, respectively.
According to the results obtained in this study contrary to current advertising about the water requirement of potato, in the case of proper management of the farm, and improved the water productivity, the potato is crop similar with other crops in rotations. Even with furrow irrigation methods, water productivity in three regions A-C-W, A-K-W and SA-K-W (based on kg m-3) was (2.99-3.94), (1.96-2.3) and (1.79-2.61), respectively. This index is more than what has been reported for grains such as wheat and barley. In potato rather than the need for water to be considered as a limiting factor, pricing strategies instability, poor management of potato planting in some areas, lack of processing industries and the lack of written policies exports are facing difficulties.