Effect of Planting Date on Yield and Different Trait Variations of Seeds from Cotton Pickings of Varamin Cultivar

The objective of this study was to evaluate the effects of sowing and picking dates on lint yield and its component, germination and seed vigor of Varamin cultivar of cotton. To this end, experiments were carried out as split-plot in time based on randomized complete block design with three replications at the cotton fields of Kizor in Sabzvar in 2013. Treatments were four sowing dates (May 8, May 20, Jun 2 and Jun 14 of 2013) and two picking dates (the harvest date of first picking for first to fourth planting dates were September23, September29, October 14 and October 27. The harvest dates of second picking for first to fourth planting dates were October 7, October 12, October 24 and November 11). Standard germination and cool germination tests for different temperatures were also performed. 1000-seed weight, number of normal seedlings and dry weight of normal seedlings were measured. Results showed that the effect of planting date, picking and their interaction effects on lint yield, seed thousand weight, number of bolls per plant, single plant weight, number of normal seedlings, dry weight of normal seedlings, germination percent, lint length and electrical conductivity were found to be significant. Highest (3693.3 kg.ha-1) and lowest (1023.00 kg.ha-1) lint yields obtained from the first picking of first planting and second picking of fourth planting, respectively. The number of normal seedlings and dry weight of normal seedlings didn’t follow a special process in standard germination test, but the number of normal seedlings produced from cool germination test of first picking with delay in sowing date was decreased in a linear form. The number of normal seedlings from alternate temperatures (one week in 18°C and the other week in 28°C) “except the first sowing date” was decreased. Results showed that by delaying sowing date (at the range of this study) seed vigor decreased. According to the results of this research, the first planting date (May 8) could be recommeded for growing Varamin cultivar for higher lint yield to this region. But, for seed production, the first picking of second planting date (May 20) is recommended.