عنوان مقاله [English]
Grapes is one of the most important horticultural products in terms of cultivation area, economic and high nutritional values. Iran with an annual production of 2.8 million tons, is among the top countries in the production of grape product in the world. However, there are not accurate information on the volume of irrigation applied water and water productivity of this product in Iran. Therefore, this study was conducted with the aim of measurement of applied water at field scale and evaluation of water productivity of grape in vineyards farms at different hubs of this crop production in Iran.
The volume of irrigation water provided by gardeners in 164 vineyards were measured in the provinces of Qazvin, Fars, Khorasan-Razavi, Zanjan, West Azarbaijan, East Azarbaijan, Hamedan, Markazi, Northern Khorasan, and Semnan as hubs of this product. These hubs covered about 80 percent of the irrigated vineyard cultivated areas. In each hub, 1-4 cities with the highest area under vineyard cultivation were selected for evaluation. The measurements were carried out in different irrigation and planting methods, various soils, different salinity of irrigation water and soil and different grape varieties during the growing season of 2018-2019 without interfering with the farmer's irrigation program. The measured values were compared with the net irrigation water requirement estimated by the Penman-Monteith method using the last 10 years meteorological data and also with the national water document values. Crop yield was recorded at the end of the growing season and water productivity was calucated as the ratio of yield to total water (irrigation applied water and effective rainfall). Analysis of variance was used to investigate the possible difference between applied water and water efficiency among the hubs. Data adequacy was assessed by using the method prposed by Sarmad et al. (2001).
Results and Discussion
The results showed that the average of applied water and water productivity among the hubs were significant at 1% probability level. The applied irrigation water used in the vineyards and water productivity were 6669 m3/ha and 2.63 kg/m3, respectively. Drip irrigation was about 20% effective compared with surface irrigation in reducing the applied irrigation water in the studied vineyards. Water productivity in drip irrigation orchards was essentially the same as surface irrigation and was not statistically significant. The reason was the lack of proper use and utilization of modern irrigation methods.
The average net irrigation water requirement in the study areas estimated by the Penman-Monteith method using meteorological data for the last 10 years as well as the national water document were 6645 and 6456 m3/ha, respectively. The range of irrigation application efficiency in the studied vineyards was from 68 to 100 and its average was 89%. Comparison of applied water and net irrigation requirement indicated deficit irrigation due to water shortage in vineyards of most hubs. In total, 31% deficit irrigation occurred in the studied vineyards, which is a threat to soil salinity and destruction of soil structure in long-term. Grape planting method had a significant effect on reducing the applied water, increasing grape yield and consequently water productivity. Scaffolding method had a positive and significant effect on all studied indices in comparison with the crawling/reptile planting method. It caused a decrease of about 15% in applied water, an increase of 41% in yield and 37% in crop water productivity.
Due to the fact that vineyards are faced with deficit irrigation and water stress, training the farmers about the accurate and scientific methods of deficit irrigation in the vineyards can be effective to reduce the destructive side effects of water stress. Due to the widespread use of surface irrigation in the vineyards, training and application of methods to improve surface irrigation performance (evaporation reduction methods, using low pressure methods such as gated pipes, mulching, etc.), to increase irrigation efficiency and to reduce irrigation water applied is recommended. Changing traditional planting methods from crawling/reptile to scaffolding and surface irrigation (qana) to furrow, in addition to reducing evaporation, are the effective ways to increase the yield of vineyards and water productivity.