The effect of irrigation management and cultivation methods of direct and transplanting on yield and yield components of cotton

Cotton or white gold is the most important and the oldest fibrous plant that is suitable for cultivation in arid and semi-arid regions. Among industrial plants, cotton has a special position. Not only cotton is one of the most important fibrous plants in view of fiber production, but also its seeds, which contain oil and protein, play a major role in providing edible oils and animal feed. Due to increasing need of society for cotton plant products and the importance of cotton in the global market and industries, it is very important to remove barriers to the continuous development of the cultivation of this product. Considering the importance of cotton in crop rotation and the sever reduction of cotton cultivation in recent years, it is necessary to use new approaches to increase the cultivation area, production amount and to reduce the production cost of this strategic crop. One of the strategies for developing the area under cotton cultivation is delayed cultivation as transplanting, which increases yield, early maturity and water use efficiency. Proper irrigation scheduling plays a very important role in delayed cultivations. In order to determine the physical and chemical properties of the soil in the study area, soil samples were taken from a depth of 0 to 30 and 30 to 60 cm and were analyzed in the laboratory. Fertilizer recommendation was done on the bases of soil test. In this experiment, the percentage of saturation moisture, electrical conductivity, acidity of saturated paste was determined and soil texture was measured by hydrometric method. Therefore, an experimental design of factorial strip plot, with three replications, was carried out in the Hashemabad cotton research station, in 2020. Irrigation methods of tape and furrow were as main factor. Cultivation methods of direct and transplanting as sub-factor and sub-sub factor was irrigation intervals after 70, 105, 140 mm cumulative evaporation from the pan, and irrigation quantities of 0, 50, 75, 100, 125% of the evaporated water from the pan. The treatment of 105 mm cumulative evaporation from the pan is usually 14 days, depending on the region. While the treatment of 70 mm means irrigating as soon as possible during 8 days. In addition, the treatment of irrigation after 140 mm of cumulative evaporation from the evaporation pan, ie once every 20 days, means that irrigation leads to plant stress. It should be noted that irrigation with less than 50% of the evaporated water from the pan can reduce the yield and is not applicable to the furrow irrigation method in the field, due to water not reaching the end of the field. In addition, irrigation with more than 125% of water evaporated from the pan is not highly recommended. The results showed that irrigation method had no effect on yield and yield components, but transplanting method had higher yield, early maturity, boll weight and water use efficiency at rates of 14, 180, 4.8 and 11.3% compared with direct method, respectively. Among the irrigation interval treatments, the irrigation after 105 mm evaporation from the pan had higher yield, boll weight and water use efficiency than the 70 and 140 mm treatments; So, that the yield of this treatment was 8.8 and 16.6% higher than the 70 and 140 mm treatments. While, water use efficiency of 105 mm treatment was 9% higher than 140 mm. In fact, cotton is a plant that reacts a lot to the amount and frequency of irrigation. It means irrigation management, and the balance between reproductive and vegetative growth is regulated by irrigation management. Excessive irrigation not only prevents increased yield, but also reduces yield and water use efficiency. Different irrigation water quantities had no effect on yield but on yield components had significant effect. The highest water use efficiency was related to 50% irrigation water, which was 19.6%, 43% and 69.8% higher than 75, 100 and 125% irrigation water, respectively. Irrigation quantity of more than 50% does not significantly increase yield but increases water use efficiency. Finally, the best treatment was transplanting method with an irrigation interval of 105 mm evaporation from the pan and 50% irrigation water of cotton increases. Also, transplanting cultivation increased yield compared to direct cultivation. Although it is not economically viable, it is recommended if the price of cotton increases.