investigation on the effect of cotton cultivars and different planting dates on barley-cotton double cropping system in gonabad climatic conditions

in order to investigate the response of cotton cultivars (gossypium hirsutum l.) to conventional-cropping and double-cropping systems a field experiment was conducted as split plot based on randomized completely block design with three replications at gonabad agriculture and natural resources research station during growing season of 2009-2010. the treatments included of recommended planting date (5th may), sowing after final irrigation of barley (22th may), sowing after harvest of barley in the same field (5th june) and three cotton cultivars: varamin, khordad and sepid. the results showed that the highest plant height (60.2 cm) was observed in second sowing date. experimental treatments did not have any significant effect on number of monopodial and sympodial branches of cotton. the highest earliness percentage was obtained from recommended planting date compared to other treatments. the highest lint weight per boll (6.5 g) was related to sowing of varamin cultivar at 3th planting date and had a significant difference with other treatments. furthermore, this cultivar at the other planting dates had relatively higher lint yield. in the case of the interaction effect between treatments on 1st pick yield, by delaying in sowing date lint yield decreased, however, khordad cultivar in recommended planting date had the highest value (1600 kg.ha-1). in the 2st harvest, only the effect of planting date was statically significant and for the 3th planting date was achieved the highest 2st pick yield. in the case of interaction, effects on total lint yield, both varamin and khordad cultivars had the same lint yields in the first planting date. although, in overall at the all planting dates khordad cultivar showed the highest lint yield. in overall, growing khordad cultivar at third planting date under double cropping after barley is appropriate in climatic conditions of gonabad.