Evaluation and analysis of water productivity indices for various crops using traditional and modern irrigation systems (case study: Tajan plain of Mazandaran)

In this study, the physical and economic productivity of water consumed by five crops (wheat, corn, forage corn, barley, and alfalfa) in Tajan plain located in Mazandaran province were investigated. Population growth, rising demand for agricultural products, unfavorable climatic conditions, dwindling precipitation, and water scarcity are among the world's most pressing problems today. According to studies, the global population will reach 7.8 billion by 2025, putting additional pressure on food security, particularly in developing countries where the population will increase by more than 80 percent. Water's physical and economic efficiency is frequently considered in analysis and decision -making. Physical productivity of water is generally defined as crop yield per cubic meter of water consumed, whereas economic productivity is calculated by dividing the net benefit by the amount of water consumed. Recent water shortages and droughts in Iran necessitate the use of appropriate irrigation techniques for crop cultivation in order to increase crop yields and better manage water resources. In this study, two traditional and modern irrigation systems were compared for the production of five crops (wheat, corn, fodder corn, barley, and alfalfa) in the province of Mazandaran's Tajan plain. In addition, the physical and economic water productivity of five crops were evaluated in order to achieve the optimal state (less water consumption, good crop yield, and high income for farmers).

Tajan catchment has an approximate area of 4005.22 km2, of which 3980.75 km2 are located within Mazandaran province and about 25 km2 are located outside the province. Tajan catchment is located eastern longitude of 53 degrees and 7 minutes to 53 degrees and 42 minutes and a northern latitude of 35 degrees and 56 minutes to 36 degrees and 17 minutes. In this study, data and information from Jihad Agriculture and Regional Water Organization were collected, including soil texture, crop water requirement, cropping area, crop yield, crop water requirement, water inflow to the farm, duration and frequency of irrigation, product prices, and investment costs. A two-stage random sampling method was employed based on the available data and information from Tajan, as well as the various cropping areas and irrigation techniques used in this region. For the study, wheat, corn, forage corn, barley, and alfalfa were chosen as crops. Notably, among the crops, corn is not cultivated using conventional irrigation techniques.

In the traditional irrigation method, the highest yield belonged to forage corn and the lowest yield. Additionally, alfalfa had the highest volume of water consumption while barley had the lowest volume of water consumption. In the traditional irrigation method, forage corn and wheat had the highest and lowest Crop Per Drop (CPD) values, respectively. Also, feed corn and barley had the highest and lowest Net Benefit Per Drop (NBPD) values, respectively. Alfalfa and barley had the highest and lowest Benefit Per Drop (BPD) indices, respectively. Therefore, barley and alfalfa, which have the lowest yield and the highest water consumption using the traditional method, are unsuitable for cultivation in this region. Additionally, in the new method, wheat has the lowest water consumption, but its performance is subpar.

Considering the obtained values of physical and economic water productivity of the aforementioned crops in the Tajan plain, it is advisable not to use traditional methods for irrigating the fields under the aforementioned cropping patterns, with the exception of fodder corn. In addition to barley and wheat, the cultivation of fodder corn, alfalfa, and grain corn is also a top priority. The cultivation of barley using either method of irrigation should be eliminated entirely.