The effect of planting dates and irrigation with Khuzestan sugarcane drainage on quantitative and qualitative properties of cotton cultivars

Due to the scarcity of fresh water resources, one of the main solutions to supply agricultural water resources is the use of unconventional water, including agricultural water drainage, saline water resources and effluents. In Khuzestan province, a total of about four billion cubic meters of drainage water is produced annually. The volume of water in the Karun Basin alone is about two billion cubic meters per year. One of the areas where sugarcane drainage has accumulated and is now a serious concern is the 35,000-hectare sugarcane wetland, located south of Ahwaz on the border with Iraq. Drainage production due to various activities, especially agriculture in Khuzestan province, is one of the serious problems. Sugarcane production and fish farming are the main producers of drainage in southwestern Khuzestan. In order to optimal use of sugarcane drainage, the effect of these waters on the quantitative and qualitative properties of cotton in the Cultivation and Sugarcane Industry of Mirza Kuchak Khan during 2018 and 2019 was investigated.

Experimental cultivation was performed in 8 lines of 30 meters with intervals of 60 x 20 cm. The field soil had a silty to loamy clay texture.. The experimental design was split-split plots with 3 replications. Three planting dates: February 28, March 29 and April 29 as the main plot, three irrigation treatments including sugarcane drainage, Karun river water, and intermittent irrigation with Karun water and drainage (combined) as a sub plot and three cotton cultivars included Golestan, Khorshid and Shayan were considered as sub-plots. The first planting date was 28th February, after plowing, disc and fertilizing. Thus, fuzzy seeds were disinfected using carboxin tiram fungicide and Gachu insecticide and then planted at appropriate depth according to field soil conditions. Irrigation planning was done based on measuring the percentage of soil moisture before irrigation and the depth of root development. Thus, in each irrigation regim, one day before the irrigation operation by measuring soil moisture to a depth of 100 cm, soil moisture deficiency is determined according to the depth of plant development by considering the maximum amount of management allowed deficit (MAD) equal to 60% of soil water holding capacity. In order to measure the yield components, five plants in each treatment were identified and measured on these plants. Cotton was harvested three times. Data were analyzed using MSTATC software and Duncan test. Finally, the best treatments were identified and introduced in terms of planting date, type of irrigation and cultivars that have better yields.

The results showed that the highest yield with 1712 kg/ ha was related to the planting date of 28 Feb. Yield of the first planting date was 42% and 574% higher than the planting dates of 29 March (1204 kg/ha) and 29 April (254 kg/ha), respectively. The total yield of cotton on the date of 29 March was 374% higher than the date of 29 April. The highest percentage of early maturity was related to the first planting date, which was not significantly different from the second and third planting date. There was no significant difference in different dates in terms of early maturity. In terms of mean boll weight, the first planting date had a higher boll weight of 11.5 and 87.6% than the second and third planting dates, but the difference between the date of the first and second crops was not significant in terms of boll weight, but The difference between these two planting dates and the third planting date was statistically significant on boll weight. The number of bolls per plant on the date of the first crop was 35 and 147% higher than the date of the second and third planting date, respectively, while the date of the second planting date had 83% more bolls than the date of the third planting date. There was no significant difference between treatments in terms of lint percentage but the second planting date had a higher lint percentage. Among irrigation water quality treatments, the yield of irrigation treatment with Karun water and intermittent irrigation with Karun water and drainage (combined) were not significantly different. Karun water irrigation had 12% higher yield than drainage irrigation, while the yield of irrigation with Karun water was only 6% higher than combined irrigation, this difference was not statistically significant. Among cotton cultivars, the highest yield with 1159 kg /ha was related to Golestan cultivar, which was 16.8% higher than Shayan cultivar. Shayan cultivar is one of the cultivars in which high temperature caused the flowers to dry out. The reason for the decrease in yield of Khorshid and Shayan cultivars was more withering and falling flowers at higher temperatures than Golestan cultivar. Golestan cultivar was more tolerant to salinity and heat stress than the other two cultivars. For this reason, it had more yield than Khorshid and Shayan cultivars and it seems to be a suitable cultivar for Khozestan. The effect of irrigation water quality treatments on fiber quality properties was not significant so that the highest strength with 26.84 was related to the date of the first planting (Feb.28), which did not differ significantly from the date of the second planting (March 29).. The effect of planting date on fiber strength at the level of 1% was significant. There was a significant difference between cotton cultivars in terms of strength and micronair at the 5% level. Shayan cultivar had the highest strength compared to the other two cultivars. The fiber strength of Golestan and Khorshid cultivars was statistically the same. Among cotton cultivars, Shayan and Golestan cultivars were significantly different from Khorshid cultivar at 5% level and had the lowest micronair. According to the results of this study, the first planting date on Feb 28 and intermittent irrigation with Karun water and drainage (combined) and Golestan cultivar is recommended for Khuzestan region.