بهینه‌سازی کاربرد کودهای نیتروژنه برای رشد و عملکرد سورگوم علوفه‌ای در سیستم‌های زراعی کم‌نهاده و متداول

In order to maintain sustainable agriculture and prevent excessive use of chemical fertilizers, supplying part of the plant needs by organic fertilizers is necessary. In this respect, effects of nitrogen (N) source and rate on yield and yield components of forage sorghum was evaluated as a factorial experiment arranged in randomized complete blocks design with three replications at the Research Farm of Shahrekord University in 2010. Treatments consisted of three N sources (urea fertilizer, cow manure and equal combination of urea fertilizer + cow manure) and three N levels )80, 160 and 240 kg/ha N, equivalent to 174, 348 and 522 kg/ha urea and 26.2, 52.5 and 78.7 Mg/ha of cow manure and equal combination of urea fertilizer + cow manure at each nitrogen level, respectively). The results showed that increase of N utilization, with increase in leaf, stem and panicle weights and stem diameter, caused a linear increase of forage yield in urea fertilizer and cow manure treatments and a quadratic increase in the combined fertilizer. The highest leaf, stem and panicle weight (600, 3789 and 823 g/m2) and also fresh forage yield (44 Mg/ha) were observed in 240 kg/ha N treatment in combined treatment. But, there was no significant difference in forage yield between this treatment and the 160 kg/ha N treatment. Overall, the results indicated that the potential of sorghum production can be increased by conjunctive use of animal manure and chemical fertilizers, even in low levels of these fertilizers, or low-input agriculture.