| Ammonia volatilization is one of the main pathways of nitrogen loss from N fertilizer applied to soil-crop system. Nitrogen fertilizers, slow-released treatments for urea nitrogen fertilizer and fertilizer application methods can directly or indirectly affect the physical and chemical properties of soil, which influence soil ammonia volatilization and nitrogen use efficiency. Slow-release processing technologies have been used in urea production to reduce ammonia volatilization and de-nitrification of nitrate in soil, so to improve crop N uptake and eventually improve nitrogen utilization. Two field trials including slow-released nitrogen fertilizers and urea placement in-situ field experiments were conducted in a sandy soil in two years in the Langfang Experimental Station of Chinese Academy of Agricultural Sciences, Hebei Province, China. The nitrogen fertilizers treatments were no nitrogen fertilizer(CK), calcium nitrate(CN), common urea(CU), polymer-coated urea(CRF), release-controlled urea(LCU), polymer gel urea(CLP) and urea formaldehyde(UF). The treatments for urea placement were no nitrogen fertilizer(CK), surface broadcasted common urea(D0) and broadcast incorporated common urea(D25). Here the ammonia volatilization characteristics, maize yield, nitrogen utilization and nitrogen balance of different control-released nitrogen and urea placement were compared to provide suggestions for their practical application. The main conclusions were as follows:1. The results show that the cumulative ammonia volatilization were significantly decreased by 72.9%, 60.8%, 37.5%, 20.3% and 19.7% from calcium nitrate(CN), urea formaldehyde(UF), polymer gel urea(CLP), polymer-coated urea(CRF) and release-controlled urea(LCU) respectively when compared with common urea(CU). The ammonia volatilization loss from fertilizer of the common urea(CU), polymer-coated urea(CRF), release-controlled urea(LCU) were higher than 60.0% in the two monitoring years, and that of the urea formaldehyde(UF) was 37.6% in average. There was a significant difference in the apparent nitrogen loss between each slow-released nitrogen fertilizer and common urea(P<0.05). The apparent nitrogen loss of common urea was the highest which was 69.5 kg/hm2 and slow-released nitrogen fertilizer can reduce the apparent nitrogen loss by 26.8%-47.6% when compared with the common urea(CU).2. The yearly average yields of other nitrogen application treatments were increased significantly when compared with the common urea(CU). The average yields of common urea(CU), urea formaldehyde(UF), polymer gel urea(CLP), release-controlled urea(LCU), polymer-coated urea(CRF) and calcium nitrate(CN) were 9571.6 kg/hm2、11341.7 kg/hm2、11043.8 kg/hm2、10834.0 kg/hm2、10881.3 kg/hm2 and 10175.0 kg/hm2. The nitrogen recovery efficiency of urea formaldehyde(UF) was the highest with an average of 57.9% which was followed by polymer gel urea(CLP), release-controlled urea(LCU), polymer-coated urea(CRF) with an average of 42.4%, 38.3% and 38.3% respectively while all of them were higher than common urea(CU), surface broadcasted common urea(D0) and broadcast incorporated common urea(D25).3. The maximum ammonia volatilization rate of surface broadcasted common urea(D0) was much higher than that of broadcast incorporated common urea(D25). The results show that broadcast incorporated common urea(D25) can reduce 84.7% of cumulative ammonia volatilization than surface broadcasted common urea(D0). The ammonia volatilization loss from fertilizer of surface broadcasted common urea(D0) was significantly higher than that of broadcast incorporated common urea(D25) with an average of 41.5% and the apparent nitrogen loss of surface broadcasted common urea(D0) was lower than that of broadcast incorporated common urea(D25) with an average 40.9%, respectively, which mean that appropriate application depth of urea can reduce nitrogen loss.4. Compared with surface broadcasted common urea(D0), broadcast incorporated common urea(D25) can increase the yield and nitrogen recovery efficiency. The average yields of surface broadcasted common urea(D0) and broadcast incorporated common urea(D25) were 9832.6 kg/hm2 and 10361.1 kg/hm2, respectively. The average nitrogen recovery efficiency of broadcast incorporated common urea(D25) and surface broadcasted common urea(D0) were 28.8% and 22.6%, respectively.Our results indicated that urea formaldehyde(UF), polymer gel urea(CLP), release-controlled urea(LCU) and polymer-coated urea(CRF) can significantly reduce the ammonia volatilization loss, improve the maize yield and nitrogen recovery efficiency. Among the tested control-released nitrogen fertilizers, urea formaldehyde and polymer gel urea perform better of them for the high-yield, high-efficiency, low-loss and low-pollution. The ammonia volatilization rate of calcium nitrate remains extremely low, but the yield is higher than common urea, so its widespread applicability deserves further validation. Broadcast incorporated with nitrogen fertilizer can significantly reduce ammonia volatilization, improve the yield and nitrogen use efficiency, which is of great significance for the sustainable development of agriculture. |
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