Introduction:

Given the increasing population, the annual decrease in precipitation, and the limited water supply resources, optimal use of existing water resources is one of the best options for creating sustainable agriculture. Maximizing irrigation water productivity has been one of the most important policies of managers and planners of the country's agricultural sector in recent years. Among the appropriate techniques for improving productivity and efficiency of water use are modern irrigation systems and the application of management scenarios such as deficit irrigation. One of the most important advances in the drip irrigation system is the invention of the subsurface drip irrigation system. Cotton is one of the most important agricultural products that, in addition to providing raw materials for the textile and oil industries, plays an important role in creating jobs in the agricultural, industrial, and commercial sectors; However, the occurrence of continuous and severe droughts in Kerman province, especially in the Orzoueyeh agricultural region, and the lack of comprehensive and citation-worthy studies and research on this issue and doubts about the economic justification of implementing these systems require that surface and subsurface drip irrigation systems for cotton crops in Orzoueyeh County be evaluated from a technical and economic perspective.



Materials and Methods:

The present study was conducted at the Orzoueyeh Research Farm affiliated with the Kerman Agricultural and Natural Resources Research and Education Center during 2024 and 2025. In order to evaluate surface and subsurface drip irrigation systems on cotton yield in Orzoueyeh County, an experiment was conducted in the form of split strip plots in a randomized complete block design with three replications. This experiment was conducted in the form of 12 treatments, three irrigation levels: I1=125, I2=100, and I3=75 percent of water requirement, and two irrigation systems including surface drip irrigation (S1) and subsurface drip irrigation (S2), as well as two drip pipe installation patterns (in all rows=L1 and one in between=L2). The factors I and S were conducted in strip and cross (factor I levels vertically and factor S levels horizontally) in each replication, and the factor L was divided into the plots resulting from the intersection of the two factors I and S. To measure and calculate the studied traits after removing the margins, the two middle lines of each plot were used. Finally, the yield of the plant per hectare, the number of bolls per plant and the water use efficiency (WUE) were measured and calculated as the amount of product per volume of water used. The studied traits were subjected to a combined analysis of variance for two years using SAS.9.2 software and the least significant difference (LSD) test was used at a probability level of 5% to compare the means. After collecting farm data to select the best treatment economically, the results were first examined using the partial budgeting method and investment priority analysis. It should be noted that sometimes, in order to determine the investment priority in the treatments under study, it is inevitable to conduct an analysis of the final rate of return on investment. In this study, too, the decision-making in the investment priority analysis was dependent on the analysis of the final rate of return on investment, which was carried out.



Results and Discussions:

Based on the results, the crop yield at the irrigation level of 100 percent of water requirement was obtained in surface and subsurface drip irrigation systems, respectively, equal to 2292 and 2555 kg/ha, and the planting pattern in all rows and in between at this irrigation level yielded 2565 and 2282 kg/ha, respectively.

The study of various indicators of crop yield, water consumption, water use efficiency, number of bolls per plant, boll weight, and the results of economic analysis of the treatments indicate the superiority of the subsurface drip irrigation system over the surface irrigation system and the superiority of the planting pattern in all rows over the planting pattern of water pipes in one between in cotton cultivation for the following reasons. The cotton crop yield in the subsurface drip irrigation system treatment is 234 kg/ha higher than that in the surface drip irrigation system. The number of bolls per plant and boll weight in the subsurface drip irrigation system are 16 and 3 percent higher, respectively, than in the surface irrigation system. The cotton yield in the all-row irrigation pattern is 254 kg/ha higher than in the one between irrigation pattern. Despite the same amount of water consumption, the water use efficiency in the all-row irrigation pattern is about 8 percent higher than in the one between irrigation pattern. The number of bolls per plant and boll weight in the all-row irrigation pattern are 12 and 3 percent higher, respectively, than in the in the one between irrigation pattern. From an economic point of view, investing in the I2S2L1 treatment (subsurface drip irrigation at 100 percent of water requirement and in a planting pattern in all rows) is preferable to investing in other treatments.



Conclusion

Investment in the I2S2L1 treatment (subsurface drip irrigation at 100 percent water requirement and in the planting pattern in all rows) is preferable to investment in other treatments. The results of the technical analysis of the project also showed that the (I2S2L1) treatment has the best statistical position (A). Considering that cotton is a water-intensive crop and the amount of irrigation has a great impact on yield, all the studied traits have a better position in the 100 percent water requirement treatment compared to the other two treatments. Therefore, it can be said that this treatment has a better ability to justify. In addition, the selection of the 100 percent water requirement treatment was made based on economic evaluation and profit for the farmer, and the low-irrigation treatment is useful for maintaining water in the field, which is not done by farmers because farmers are always looking for profit.