تأثیر منابع مختلف کود‌های محتوی نتیروژن پایه برعملکرد، کارایی و درصد بازیافت نیتروژن در گندم

To increase grain yield, nitrogen use efficiency (NUE) and nitrogen apparent recovery fraction (NARF) in wheat (Triticum aestivum L.), an experiment was carried out in Karaj Soil and Water Research Station farm for two consecutive growing seasons in 2004-05 and 2005-06. The experimental design was RCBD with 6 treatments (T1= Control T2= 150 kg ha-1 of N as urea in 3-split applications T3= 1/3 N as SCU as the base fertilizer + 2-split urea applications T4= 150 kg ha-1 N as SCU as the base fertilizer T5=150 kg ha-1 of N as urea in 2-split applications and T6=1/3 N as complete fertilizer as the base fertilizer +2-split urea applications) in the first year and 7 treatments (T1= Control T2= 180 kg ha-1 of N as urea in 2-split applications T3= 180 kg ha-1 of N as urea in 3-split applications T4= 180 kg ha-1 N in 5-split urea applications T5 = pre-plant urea + 4-split urea applications T6= 1/3 N as SCU as the base fertilizer +4-split urea applications and T6=1/3 N as complete fertilizer as the base fertilizer +4-split urea applications) in the second year with 3 replications. In the second year, N rate was increased from 150 to 180 kg ha-1, adding the existing extra nutrients in complete macro and fertilizers to other treatments and N split-application was increased up to four times. After harvesting, grain yield, NUE and NARF were measured. The results of first year revealed that the yield, NUE and NARF for T2 (5145 kg ha-1, 13.8 kg kg-1, 41.2%, respectively) and T6 (5067 kg ha-1, 13.2 kg kg-1, 38.2.2%, respectively) were increased significantly at 1% level. In the second year, the maximum grain yield (6335 kg ha-1), NUE (16.2 kg kg-1) and NARF (50%) were obtained again from T6 treatment. Higher yield, NUE and NARF in the second year were mainly due to higher N rates and more N split applications. The economic returns for these substitutions, even without considering any fertilizer subsidies, the averages turned out to be 14, 8 and 4 in these treatments, respectively. Overall results revealed that the substitution of complete macro and SCU fertilizers with pre-plant urea is advisable in wheat production areas. Therefore, it is recommended that the experiment be further tested and evaluated in some wheat growing provinces.l results.