EFFECT OF PLANTING DATE AND NITROGEN RATE ON YIELD AND QUALITY OF FORAGE CORN

To study the effects of planting date and nitrogen rate on yield and quality of forage corn (Zea mays L. cv. SC704), an experiment was conducted in Isfahan, Iran, in 2011. Layout of the experiment was a factorial design with three randomized complete blocks. Factors were N rates (0, 50, 100, 150, and 200 kg ha^-1) and planting dates (14 June and 25 June). Result showed that fresh and dry forage yields were significantly increased by 137% and 115%, respectively, as N rate increased from 0 to 200 kg ha^-1. Fresh and dry forage yields were significantly higher in planting date of 25 June compared with planting date of 14 June. Regardless of planting date, total aboveground N and P uptake responded linearly to nitrogen rates. Averaged across planting dates, total aboveground N and P uptake were significantly increased by 4.4 and 6.1 times when N fertilization increased from 0 to 200 kg ha^-1. A delay in planting date from 14 June to 25 June increased significantly aboveground N and P uptake as averaged across N rates. Based on the results of this experiment, application of 200 kg N ha^-1 and planting date of 25 June are recommended for forage corn production in Isfahan.