Effect of sowing date on growth and seed yield of soybean (Glycine max Merrill) genotypes under North Khuzestan weather conditions

The optimum sowing date and genotypes adapted to climatic conditions of target regions play significant role in achieving the maximum crop yield. To investigate the interaction of soybean genotypes to sowing date, a field experiment as split ararngements in radomized complete block design with three replications was carried out in Safiabad Agricultural Natural Resources Research and Education Center of Dezful, Iran for two successive seasons (2014-15). Main plots consisted five levels of sowing date (21st June, 5th July, 20th July, 3rd August and 17th August) and subplots included; 7 genotypes (2001, 2002, Persing × Epps, Saman, Migmat, SG20 and Salend). Results showed that the highest number of pods per plant (66) belonged to cv. Salend in second sowing date (5th July) and the lowest (17.7) belonged to genotype 2001 in sowing date 17th August. Results showed that sowing date had significant effect on plant height, and delaying in sowing date led to decrease of plant height in all genotypes and increased growth duration. The results of combined analysis of variance showed that effect of sowing date was significant on seed yield. The highest (3479 kg.ha-1) and the lowest (1698 kg.ha-1) seed yield belonged to sowing dates of 21st July and 18th August, respectively. Average of two years revealed that Salend and SG20 had higheer seed yield. Migmat had the highest seed protein content in all sowing dates. The highest oil content (25.9%) obtained in the second sowing date and genotype 2001. The lowest oil content (21.6%) belonged to cv. Saman in the last sowing date (17th August). Considering the results of this experiment and crop rotation in the region, soybean genotypes (group VI-VII) and sowing date in late of July can be recommended for North Khuzestan conditions.