Introduction

Most regions in Iran are classified as arid and semi-arid areas. The management of water resources in the agricultural sector holds great significance as it is the largest consumer of water in the country. To effectively plan and manage these resources, it is imperative to possess adequate information regarding the water consumption across different agricultural products. Given the country's reliance on sweet lime products, and the limited research conducted in this area, determining the water usage in sweet lime orchards could prove valuable for national planning and decision-making. A thorough review of existing literature indicates a wealth of information on water requirements and the impact of various irrigation methods on citrus fruit yield worldwide. However, there is a dearth of research specifically focused on irrigating sweet lime trees under the guidance of gardeners. In Iran, the management of sweet lime irrigation has also received limited attention. Therefore, this study aims to quantify and evaluate the volume of water applied and the water productivity of sweet lime trees in the country.

Methodology

In this particular field study, the direct measurement of irrigation water volume and sweet lime yield was carried out in a total of 67 selected orchards located in the provinces of Fars and Hormozgan. The fruit yield was acquired over a span of three consecutive years, and the average yield was subsequently utilized in the subsequent analysis. The investigation into potential discrepancies in yield, irrigation water volume, and water productivity in the production of sweet limes was conducted through the utilization of analysis of variance. By closely monitoring the irrigation program of the gardens and assessing the cultivated area, the inflow of water to the garden was determined, subsequently allowing for the measurement of the volume of irrigation water employed by the sweet lime trees in each individual garden. The multiplication of the flow rate throughout the entire irrigation period in the season yielded the precise amount of irrigation water volume. Additionally, various factors such as the soil texture of the gardens, the electrical conductivity of both the soil and irrigation water, among others, were measured in each respective garden. The evapotranspiration of the sweet lime trees in each region was calculated by employing the meteorological data from the station closest to the project implementation area over the course of the last ten years, as well as the year of the research, using the Penman-Montieth methodology. The obtained results were subsequently compared to the calculated net required irrigation water and the values outlined in the National Water Document (NETWAT).

Results and Discussion

The outcomes revealed that there were significant disparities in the output, quantity of water applied, and indicators pertaining to water efficiency within the aforementioned regions. The average yield of sweet lime per unit area was determined to be 22.3 metric tons per hectare. The mean volume of irrigation water used and the total amount of water applied were found to be 14,192 cubic meters and 15,144 cubic meters per hectare, respectively. The mean water productivity in terms of irrigation water was estimated to be 1.70 kilograms per cubic meter. The weighted average water productivity considering both irrigation water and long-term effective rainfall amounted to 1.47 kilograms per cubic meter. Similarly, the weighted average water productivity considering both irrigation water and current year effective rainfall was calculated to be 1.60 kilograms per cubic meter. The proportion of irrigation water volume used in sweet lime orchards with respect to the overall water requirement in the selected provinces was found to be similar. In general, the average difference between the depth of irrigation water and the annual and long-term gross water requirement in the country was found to be -1 percent and +17 percent, respectively. Factors such as water and soil salinity, tree age, gardener literacy level, and soil texture were identified as some of the variables that influenced the yield, water productivity, and volume of irrigation water.

Conclusions

Accurate determination of the required water for plants and the volumetric delivery of water can yield highly effective results in terms of reducing irrigation water usage and increasing water productivity. Furthermore, the adherence to irrigation scheduling in sweet lime orchards has the potential to optimize the yield per unit of water allocated. When establishing or renovating sweet lime orchards, it is advisable to select cultivars that are resilient to cold and salinity, possess export capabilities, and expand the cultivation area in proportion to the available water resources.