Introduction: Cotton is one of the most important fiber plants in Iran which needs more production for national fiber sufficiency goal. Its cropping area in Iran is now about 140,000 ha in which 95.3% is irrigated; rainfed cotton is growing only in Khorasan, Golestan and Mazandaran. Planting date and nutrition management and their interactions are amongst the most important determinants of crop yield.
Material and methods: Field experiment in 2016 in the fields of Cotton Research Center of Golestan province in Hashem Abad split plot factorial in a randomized complete block design was conducted. Treatments include the planting date as the main factor, cultivar (Latif and Golestan) and nitrogen (three levels: desirable, a third desirable and without fertilizer) as sub plots. The first planting date in the traits (TDM, LAI, CGR and RGR) was superior to the second planting date. Among the cultivars, Golestan cultivar showed a better response to Latif cultivar at zero fertilizer level and 160 kg ha-1 nitrogen fertilizer.
Results and discussion: TDM variation and LAI of cotton cultivars during the growing season were three stages. The first stage, the phase of presentation, in which the TDM variations continued up to 55 and 61 days after planting and the rate of changes in the LAI, respectively, was 55 and 43 days after planting in the first and second planting dates. TDM accumulation changes up to 109 and 96 days, the LAI was about 88 and 96 days, the RGR was 55 and 61 days, and the CGR was 88 and 96 days after planting in the first and second plantings increased linearly. Maximum RGR and CGR were observed at cultivar Golestan cultivar at zero and 160 kg ha-1 in first planting date.
Conclusion: In general, first planting date (29 June) in comparison with the second planting date (12 July) caused higher DM production, LAI, RGR and vegetative growth and Golestan cultivar had better performance than Latif cultivar at 0 and 160 khNha-1. The maximum RGR at these two-fertilizer level in Golestan cultivar was recorded at the first planting date which caused a significant difference for the time reaching maximum LAI.