Simulation of the effect of planting date on cotton yield and water use efficiency using SSM -Crop model

Cotton as one of important crop products in Iran has special role and needs to increase its production to achieve self-sufficiency. The correct methods of crop management, including planting date are in order to determine the most appropriate growth conditions to increase yield and maximize productivity of the growing environment. Planting date of cotton is very important due to environmental limitations and coincides the sensitive period of cotton with severe summer heat and cultivation of two crops and early and late cold at the beginning and end of the season. The objective of this study was to obtain the best planting date in view of cotton high yield and increasing of water use efficiency.

In this study, 35 year (1984-2018) statistical data of Hashem Abad Meteorological Synoptic Station of Gorgan (precipitation, maximum and minimum temperatures, daily solar radiation) entered into the weather and product calibration model (SSM-Crop) and defines 11 planting date scenarios in the weather and product calibration model (SSM-Crop) (13 and 23 April, 3,13 and 23 May, 2, 12 and 22 June, 2, 11 and 22 July) was evaluated cotton yield changes and water use efficiency as well as its statistical characteristics during different years with different climatic conditions.

The results of predicted yield and water use efficiency in climate and crop model (SSM‌‌-Crop) showed that by delaying in cotton planting date, average cotton yield decreased but based on t-test Student results, there was no significant difference on cotton yield at the level of 5% in planting dates of related to scenarios of 23 April, 3 and 13 May. There was an increasing trend for average water use efficiency from 13 April to 23 May scenarios and then, from the 23 May to the 22 July scenario, was decreasing trend so that the highest and the lowest values were 10.07 and 1.75, related to 23 May to the 22 July scenario, respectively.

Cotton is a plant that planting date can play an effective role in yield and water use efficiency, but the best planting date regarding to calibrated climate and crop model was obtained from 5 May to 21 May. Delaying in planting date was not recommended so farmers Due to reduction in average cotton yield and water use efficiency. Because of delaying and cultivation of two crops during year in most farming fields of Gorgan. transplanting method can be recommend for obtaining of higher yield and optimum use of water in cotton.