Abstract
Nitrogen (N) losses from agriculture through leaching and volatilization have significant environmental and economic impacts. To find better options for reducing N losses, different N management approaches were compared to determine leaching losses of Nr (NH4+-N and NO3−-N) and ammonia (NH3) volatilization from wetland rice. The experiment comprised seven treatments, viz., zero N (control), recommended dose of N (RDN), 125% of RDN (RDN125), 75% of RDN (RDN75), cowdung 2 t ha−1 + supplemented N (CDSupN), biochar 2 t ha−1 + RDN (BRDN), and deep placement of urea super granules (USG). The recommended N rates of prilled urea were 186 kg ha−1 in the Boro (dry season) and 102 kg ha−1 in the Aman (wet season), while those for USG were 95 kg ha−1 in the Boro season and 75 kg ha−1 in the Aman season. The study was conducted in four consecutive seasons of Boro and Aman rice. Leaching losses of NH4+-N varied between 1.3 and 9.4 kg ha−1 in the Boro season and 0.9 and 5.9 kg ha−1 in the Aman season, while leaching of NO3−-N ranged from 1.4 to 11.8 kg ha−1 in Boro season and 0.7 to 4.4 kg ha−1 in Aman season. During the four consecutive rice growing seasons, N leaching and NH3 volatilization losses followed the order of RDN125 > RDN > RDN75 > CDSupN > BRDN > USG > control. Compared with the applied N, the N leaching losses were only 3% in the BRDN and 4–5% in the USG treatments which were almost half that of the RDN125 and RDN treatments. In proportion to the applied N, the N volatilization losses were only 8–9% in the BRDN and 5–6% in the USG treatments which were almost half as that in the RDN125 and RDN treatments. Losses by NH3 volatilization exceeded losses by leaching across all N treatments. Compared with the RDN treatment, grain yield increased by 15% in the BRDN and 8% in the USG treatments in the Boro season, while for the Aman season there was a 17% increase in the BRDN and 9% in the USG. Biochar with RDN and USG had the greatest potential to reduce N losses without loss of rice yields and can therefore be recommended as improved practices for rice-growing farmers.
Abstract
Nitrogen (N) losses from agriculture through leaching and volatilization have significant environmental and economic impacts. To find better options for reducing N losses, different N management approaches were compared to determine leaching losses of Nr (NH4+-N and NO3−-N) and ammonia (NH3) volatilization from wetland rice. The experiment comprised seven treatments, viz., zero N (control), recommended dose of N (RDN), 125% of RDN (RDN125), 75% of RDN (RDN75), cowdung 2 t ha−1 + supplemented N (CDSupN), biochar 2 t ha−1 + RDN (BRDN), and deep placement of urea super granules (USG). The recommended N rates of prilled urea were 186 kg ha−1 in the Boro (dry season) and 102 kg ha−1 in the Aman (wet season), while those for USG were 95 kg ha−1 in the Boro season and 75 kg ha−1 in the Aman season. The study was conducted in four consecutive seasons of Boro and Aman rice. Leaching losses of NH4+-N varied between 1.3 and 9.4 kg ha−1 in the Boro season and 0.9 and 5.9 kg ha−1 in the Aman season, while leaching of NO3−-N ranged from 1.4 to 11.8 kg ha−1 in Boro season and 0.7 to 4.4 kg ha−1 in Aman season. During the four consecutive rice growing seasons, N leaching and NH3 volatilization losses followed the order of RDN125 > RDN > RDN75 > CDSupN > BRDN > USG > control. Compared with the applied N, the N leaching losses were only 3% in the BRDN and 4–5% in the USG treatments which were almost half that of the RDN125 and RDN treatments. In proportion to the applied N, the N volatilization losses were only 8–9% in the BRDN and 5–6% in the USG treatments which were almost half as that in the RDN125 and RDN treatments. Losses by NH3 volatilization exceeded losses by leaching across all N treatments. Compared with the RDN treatment, grain yield increased by 15% in the BRDN and 8% in the USG treatments in the Boro season, while for the Aman season there was a 17% increase in the BRDN and 9% in the USG. Biochar with RDN and USG had the greatest potential to reduce N losses without loss of rice yields and can therefore be recommended as improved practices for rice-growing farmers. Read More
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