Determination of water use and water productivity of commercial cotton cultivars

Background and Objectives: Crops with high WUE and appropriate irrigation methods are critical for irrigation water management. Because of the indeterminate growth habit of the crop, this issue is particularly important in cotton production. Under high irrigation conditions, the balance between vegetative and reproductive growth may be upset. There are many reports showing the superiority of belt irrigation methods over conventional methods such as furrow irrigation. Considering the limited water resources in Iran, this experiment was conducted to study the response of cotton cultivars to irrigation rates and methods.
Materials and Methods: In this experiment, foreign and domestic commercial cotton varieties were compared in terms of yield and water use efficiency (WUE), in the form of split blocks on CRBD with 3 replications in 2022-2023 cropping seasons. Irrigation after 30% and 100% water evaporation from the pan in the main blocks. 13 cotton varieties were established in sub-blocks (plots) as sub-factors. Cultivars included of Golestan, Latif, Sepid, B557, Khordad, Partow, Taban Mai, Maxa, Lider, Loduz and American Genetics.
Result: the effects of treatments on all traits studied were significant. The interaction between irrigation and cultivar on the traits was significant, except for the number of sympodial branches and fiber content. In the first year, the yield of Golestan and Partov cultivars was higher than the others when irrigated after evaporation of 30% of the husk water. Golestan, B557 and Khordad had higher yield when irrigated after 100% evaporation, which was due to their ability to form and retain more bolls per plant. Sepid and Lodouz varieties had the lowest yield in the first year. In the second year, Golestn and Khordad were superior to the other cultivars when irrigated after 30% pod evaporation. When irrigated at 100% evaporation from the pan, Golestan, Mai, and Taban had higher yield. The lowest yield this year was obtained by Leeder and Loduz varieties when irrigated after 30% evaporation from the pan. The most likely reason for these yield losses was the loss of balance between vegetativeand reproductive growth, which resulted in completely excessive growth, especially in the Loduz variety. This higher vegetative growth resulted in a reduction of the WUE value.
Conclusion: the local cultivars Golestan, Khordad and Partow and the Turkish cultivar Mai showed higher yields under belt irrigation. Due to the high vegetative growth potential in Leeder and Golestan, irrigation management of these varieties is more important than that of the others.