ارزیابی بهره‌وری اقتصادی آب در کشت کینوا با کاربرد آب شور و کم‌آبیاری در سیستم آبیاری قطره‌ای نواری در استان فارس

Introduction

Agriculture remains a cornerstone of the economy in many developing countries, contributing significantly to gross domestic product and ensuring food security. In Iran, agricultural development faces particular challenges due to water scarcity, as national rainfall averages only one-third of the global mean and its temporal and spatial distribution often misaligns with agricultural demand. Furthermore, water salinity has emerged as a major global environmental issue. One approach to mitigating salinity stress is the cultivation of salt-tolerant crops, such as quinoa (Chenopodium quinoa Willd.), which can thrive in highly saline conditions. In addition, drip irrigation particularly tape drip systems offer advantages such as reduced water loss, and improved crop quality. It enables precise and uniform water application directly to the root zone, helping maintain matric potential and mitigating osmotic stress associated with saline irrigation. Quinoa is a resilient crop with high nutritional value, exceptional adaptability to harsh environmental conditions, and potential to enhance food and nutritional security, especially in arid and semi-arid regions. Its high market value and low production costs make it a promising option for sustainable agriculture. However, salt tolerance varies among quinoa cultivars, and limited research exists on its field performance under drip irrigation systems in saline and deficit irrigation conditions, particularly in Iran. Given this context, the present study aimed to assess seed yield, water productivity, economic evaluation, and determine economic water productivity of quinoa cultivated with saline water and under deficit irrigation using a tape drip system in the Bajgah region of Fars Province.

Materials and Methods

A field experiment was conducted at the Research Farm of the Water Engineering Department, Faculty of Agriculture, Shiraz University (located in Bajgah, 16 km north of Shiraz; 32°52′ N, 32°29′ E; elevation: 1810 m above sea level). The study followed a factorial-split plot design in a randomized complete block with three replications. The treatments included: Four irrigation water salinity levels: 0.6, 5, 15, and 25 dS.m^-1 (designated EC1 to EC4), Two irrigation levels: full irrigation (FI) and 50% of full irrigation (0.5FI), Three quinoa cultivars: Titicaca, T1, and Giza-1. Irrigation was applied using a tape drip system with emitters spaced at 10 cm intervals and a discharge rate of 2 L.ha^-1. Data were analyzed using analysis of variance (ANOVA) and the LSD test for mean comparisons, performed in SAS 9.4. To evaluate the economic feasibility of quinoa cultivation under the experimental treatments, engineering economic methods including net present value (NPV (, and benefit-cost ratio (BCR) were employed.

Results and Discussion

The highest seed yield (3106 kg.ha^-1) was observed under full irrigation with 0.6 dS.m^-1 irrigation water salinity. Under full irrigation, seed yield declined by 5.88%, 31.6%, and 50.3% with increasing irrigation water salinity (from 0.6 to 5, 15, and 25 dS.m^-1, respectively). Under deficit irrigation, yield reductions were more pronounced 21.3%, 36.5%, and 49.7% for the same irrigation water salinity levels. Water productivity improved under deficit irrigation but decreased with rising irrigation water salinity. The maximum water productivity (0.84 kg.m^-3) was achieved by the Titicaca cultivar under 50% irrigation with 0.6 dS.m^-1 salinity. In contrast, the lowest value (0.34 kg.m^-3) occurred at 25 dS.m^-1 salinity with full irrigation.

For economic evaluation, a quinoa selling price of $2.06 per kg was assumed. The highest NPV, BCR, and economic water productivity were recorded under full irrigation and 0.6 dS.m^-1 salinity. The BCR exceeded one for all salinity levels under full irrigation, except at 25 dS.m^-1. Under deficit irrigation, the BCR was below one across all salinity levels due to significant yield losses. Notably, even under salinity levels as high as 15 dS.m^-1, quinoa cultivation under full irrigation remained economically viable. Among the cultivars, Titicaca exhibited the highest economic performance with a BCR of 1.15, followed by Giza-1 and T1, both with a BCR of 1.13.

Author Contributions

All authors contributed equally to the conceptualization of the article and writing of the original and subsequent drafts.

Data Availability Statement

Data will be made available on request.

Acknowledgements

The authors gratefully acknowledge Shiraz University Research Council, the Drought Research Center, the Center of Excellent for On-Farm Water Management, and the Iran National Science Foundation (NSF) for funding.

Ethical considerations

The authors avoided data fabrication, falsification, plagiarism, and misconduct.

Conflict of interest

The author declares no conflict of interest.