Kumara H.G.J.T.1, Nissanka S.P1, Gunawardane M2, Abeysiriwardane D. S. De Z.3
1Department of Crop Science, Faculty of Agriculture, University of Peradeniya, Peradeniya, Sri Lanka. firstname.lastname@example.org
2SLINTEC, Nanotechnology and Science Park, Mahenwatte, Pitipana, Homagama, Sri Lanka
3CIC Agri Businesses (Pvt) Ltd, Pelwehera, Dambulla, Sri Lanka
Agronomic efficiency of N (AEN) in rice cultivation ranges from 20-40 % due to heavy losses of applied N. Dicyandiamide (DCD) and N-(n-butyl) thiophosphorictriamide (NBPT) are used for some crops to enhance the efficiency of urea fertilizer and reduce ammonia volatilization, respectively. The DCD and NBPT were evaluated in combination with different levels of the recommended rate of urea by the Department of Agriculture (DOA), Sri Lanka to examine the (AEN) in irrigated rice (Oryza sativa L.), conducting a pot experiment. As treatments, three levels of urea (100 % (225 kg Urea/ha), 75 % and 50 % of the DOA recommended rate) in the form of urea, and inhibitor compound with four levels (no compound, only NBPT, only DCD and combination of NBPT + DCD) and a control of no urea applied, were arranged in a Completely Randomized Design (CRD) with three replicates. The DCD and NBPT rates were 10 % and 1 % of the amount of urea used, respectively. Results showed that 50 % urea with inhibitors had no significant yield reduction (P>0.05) compared to 100 % urea alone, with a greater AEN. Thus, application of urea with DCD and NBPT lead to a significant reduction in amount of urea application.