Introduction: Cotton, as one of the most important crops in the country, has a special place due to its important role in human and livestock nutrition, health, the clothing industry, and job creation, so it is known as white gold among farmers. Sometimes, due to unsuitable climatic conditions, cotton planting faces problems that can be partially resolved by agricultural operations. Proper germination and establishment of crops are among the most important and fundamental factors that affect the economic performance of the crop. Pretreatments are one of the seed improvement techniques that can increase the percentage of germination and emergence, and increase the range of seed germination in stressful environmental conditions such as temperature and drought. Increasing seed quality by pretreatments, in addition to enhancing germination characteristics and better establishment of seedlings, also increases the final yield.
Materials and Methods: This study aimed to investigate the effect of pretreatment of cotton seeds with powdered humic acid containing Zn at different planting dates, using a split plot experiment in a randomized complete block design with three replications on the Golestan cotton variety at the research farm of the Agricultural Research and Education Center and Natural Resources of Ardabil Province (Moghan Station) in the 1402-1403 crop year. Sowing dates in the main plots were at 4 levels (May 2 and May 15, June 2 and June 10), and seed dressing with powdered humic acid containing zinc at 3 levels (2, 3, and ppm) and a control treatment without seed dressing. The humic acid used in this design contained 60% humic acid, 15% fulvic acid, and 2% zinc.
Results and Discussion: The results of this study showed that seed pretreatment with powdered humic acid at different sowing dates had a significant effect on germination characteristics of cultivated seeds and final and harvested yield. Seed treatment with humic acid at a ratio of 3:1000 had the greatest effect on germination percentage, germination rate, average germination time, seed vigor index, D10 (ten percent emergence), and D90 (ninety percent emergence) at the sowing date of May 15. Also, pretreatment at a ratio of 4:1000 reduced the negative effects of late sowing dates (May 2) and early planting dates (June 15) on germination components, especially germination rate, by 11%. In addition, seed pretreatment with humic acid at ratios of 3 and 4 had the greatest effect on first and total yields. The highest first-row yield of 4700 kg/ha was obtained in seed pretreatment with humic acid at a ratio of 4:100, and the total yield of 7150 kg/ha was also obtained in this treatment. Also, the highest first-row yield of 5210 kg/ha was obtained on the planting date of May 15, and the lowest was 1700 kg/ha on the planting date of June 10. In addition, the highest total yield of 6685 kg/ha was obtained on the planting date of May 15 (as the appropriate planting date), and the lowest was 1845 kg/ha on the planting date of June 10 (as the late planting date).
Conclusion: Overall, the use of humic acid as a pretreatment is a cheap and easy method that improves germination traits, enhances early growth of cotton seedlings, and final cotton yield. Also, the best planting date for successful cotton cultivation in the conditions of the Moghan Plain was found to be May 15, which is recommended as the most suitable planting date. The planting date of June 10, which is sometimes used as a second crop in cotton cultivation on the Moghan Plain, was not suitable due to the short growing season and exposure to late-season cold.