تأثیر کاربرد نیتروژن و تقسیط آن بر عملکرد، درصد ماده خشک غده و شاخص برداشت سیب‌زمینی رقم مارفونا

A two-year study (2007-2008) was carried out to explore the effect of split application of nitrogen fertilizer on yield, dry matter and harvest index of Marfona potato cultivar in Isfahan Agricultural Research Center, Iran. A randomized complete block design with a split plot arrangement with three replications was used. The main plots were three levels of nitrogen (100, 200 and 300 kg ha-1) and the subplots comprised of three application rates of the fertilizer (non-split application of nitrogen before planting, split application of nitrogen fertilizer at the 5-6 leaf and rapid growth of tubers stages, and split application of nitrogen fertilizer at the two-leaf, the 5-6 leaf and rapid growth of tubers stages). The results indicated that the maximum tuber yield of 43,210 kg ha-1 was obtained with 300 kg ha-1 N and three times of N split applications, however, this treatment resulted in the lowest percentage of tuber dry matter (6.2%). The harvest index ranged from 65 to 75 percent, with the highest HI resulting from application of 300 kg ha-1 N, with 75 and 73 percent in two and three times split applications, respectively. The highest non-marketable yields were 3350 and 3280 kg ha-1 and obtained from 300 kg ha-1 N treatment and three and two split applications, respectively. In summary, the results revealed that the optimum amount of nitrogen application rate for the environmental conditions of this study depending on seeking maximum tuber yield or tuber dry matter is different. To achieve the maximum tuber yield and tuber dry matter percentage, 300 kg ha-1 N with three split application times, and 200 kg ha-1 N with two split application times are recommended, respectively.