HOSSEIN SABAHI1, AMIR GHALAVAND2
1Shahid Beheshti University, Agroecology, Iran
2Tarbiat Modares University, Agronomy, Iran
Farmyard manure is a valuable source for plant nutrition, but high N loss and low N fertiliser use efficiency are serious challenges fronting them. In attention to environmental importance of this problem, we suggested this 2-year experiment on winter rapeseed (Brassica napus L.) in rainfed condition (average precipitation was 700mm). Treatments conclude 0, 50,100, 150, 200kg N ha-1 urea (fertiliser treatments), 150kg N ha-1 urea + 50kg N ha-1 manure (Int1), 100kg N ha-1 urea + 50kg N ha-1 manure (Int2), 50kg N ha-1 urea + 100kg N ha-1 manure (Int3), 150kg N ha-1 manure (Org). The inorganic fertiliser plots also received 25kg P ha-1 and 50kg K ha-1. Optimum fertiliser treatment was 150kg N ha-1. The greatest seed yield (3 t ha-1) obtained in 150kg N ha-1 + 50kg N ha-1 treatment in two year. Seed yield for organic treatment (org) was nonsignificantly lower in 2002 (2.3 vs. 2.5 t ha-1) and significantly greater in 2003 than optimum fertiliser treatment (2.9 vs. 2.6 t ha-1). Results also showed that Int2 and Int3 treatments decrease N loss (4 and 9.5kg N ha-1 yr-1 respectively) compared to manure (25.5kg N ha-1 yr-1) and optimum inorganic fertiliser (38.5kg N ha-1 yr-1). Apparent N use efficiency was calculated as [(total treatment N uptake in 2 yr -- total check N uptake in 2 yr)/ N applied in 2yr] 15#15100. This was 20% for manure (org), 57% for Fropt, 37% for int2 and 24% for int3. This difference may be due to remained 57% of N in soil from manure treatment at final of experiment. The greatest physiological N use efficiency (average 26%) was obtained in Int3 treatment, this can be due to better synchronisation of N release and crop uptake.
Keywords: winter oilseed rape, N loss, N-use efficiency , nitrogen, organic