Determining the volume of applied water and water productivity of the lemon orchards in Fars province

About 34% of the lemon produced in the country is obtained from Fars province. This province, like many parts of the country, is one of the arid and semi-arid regions, and water management is of particular importance in it. In order to better plan and manage water resources and increase the amount of crops and water productivity of farms and gardens, sufficient information should be available on the amount of water used in different crops. Considering the importance of lemon fruit in Fars province and conducting little research on the amount of irrigation water for this product in the country, it can be useful to investigate this index and the water productivity of this product in the Fars province.

In this project, the water productivity and the amount of irrigation water given by gardeners for lemon production during one year (2021) were measured without providing technical or expert advice to the gardeners. The location of the research was the seven most important cities in Fars province in terms of lemon cultivation area, including Qhir-Karzin, Jahorm, Darab, Lar, Kazerun, Farashband and Mohr. In each city, 10 gardens and a total of 70 gardens were selected for data collection and monitoring. The desired gardens in the cities were identified and selected with the help of experts from the agricultural jihad organizations of the provinces. The studied lemon orchards were selected in such a way as to cover various factors such as irrigation method, soil texture, variety and quality of irrigation water. The yield was obtained in three consecutive years and their average was used in the analysis. The selected gardens were all equipped with drip irrigation system. The amount of discharge from the water source was measured by calibrated meter in each of the selected gardens three times a year. After determining the flow rate of water entering the orchard, by carefully monitoring the irrigation program of the orchard and also measuring the area under cultivation, the volume of irrigation water for lemon trees in each of the selected orchards was measured. The amount of evapotranspiration of lemon trees in each region was calculated using the meteorological data of the nearest station to the project implementation area in the last 10 years and the year of conducting the research using the Penman-Montieth method. The values of net required water of lemon were also obtained from the National Water Document. The gross required water of gardens was obtained and compared with the irrigation water volume of gardens by t-test. Variance analysis was used to investigate yield changes, irrigation water volume and water productivity in lemon production in the target cities.

Among the selected orchards, due to differences in irrigation management, soil salinity and other factors, the amount of irrigation water volume varied from about 6000 to 21000 m3/ha/yr. The average total volume of irrigation water was 13376 m3/ha. In terms of regional average, the lowest and highest amount of irrigation water volume was related to Jahrom and Darab with 10030 and 16433 m3/ha, respectively. The average total volume of applied water, in which the amount of effective rainfall is added to the volume of irrigation water, was estimated to be 14407 m3/ha/yr. The range of changes in the volume of applied water in gardens varied from about 7000 to 22000 m3/ha. Therefore, it can be said that the contribution of rainfall in the year of conducting the research was on average about 100 mm or 1000 m3/ha. In terms of volume of applied water, the highest and lowest amount belonged to Kazerun and Jahorm cities with 18799 and 10768 m3/ha, respectively. Irrigation water productivity in selected orchards ranged from 0.69 to 3.21 kg/m3 and averaged 1.52 kg/m3. Comparing the volume of irrigation water with the gross water requirement in different areas showed that in some regions over-irrigation and in some deficit irrigation was done. But in general, the average difference between the volume of irrigation water and the annual gross water requirement was 255 m3/ha, which was not statistically significant. However, the volume of irrigation water at the rate of 1735 m3/ha was more than 11640 m3/ha of long-term gross water requirement, which was statistically significant at the level of 1%. Therefore, it is necessary to apply irrigation scheduling and determine the exact water requirement to increase the productivity of the lemon orchards in Fars province.