Effects of chlorine-containing nitrogen fertilizer on ammonia volatilization and yields under rice–wheat rotation system in Taihu Lake region

ObjectivesWith the aim of marketing a new technological chlorine-containing fertilizer with decreasing environmental risk, we gained insight into crop yield, nitrogen use efficiency (NUE), ammonia volatilization, soil residual chlorine and pH in soil from rice–wheat rotation system with addition of urea, ammonium chloride and urea-ammonium mixed nitrogen fertilizer (urea∶ammonium chloride = 1∶1, manufactured with tower spray granulation technology, UAMF) in Taihu Lake region.

MethodsTaking the no fertilizer application (CK) and conventional urea application (U) as two controls, effect of the chlorine-containing N fertilizer was studied through a two-rotation filed plot experiment in Taihu Lake region. The chlorine residual at the depths of 0–20 cm and 20–40 cm soil after the harvest was determined with the mercury thiocyanate spectrophotometry. The NH₃ volatilization was measured by a dynamic chamber method.

ResultsThere were no significant differences in statistics among grain yields for the applied urea, ammonium chloride and UAMF. But compared with the urea fertilizer, the UAMF had a higher trend for the rice and wheat yields and the ammonium chloride had a lower trend for the wheat yield. In addition, the UAMF significantly increased the NUE by 7.0% compared to the urea application (P < 0.05). The NH₃ volatilization occurred primarily during the rice season rather than during the wheat season. Compared to the NH₃ volatilization from the urea, the NH₃ volatilization amounts of the ammonium chloride were decreased by 26.3% (1.39 kg/hm²) in wheat season but increased by 10.4% (2.67 kg/hm²) in rice season. In contrast, the UAMF presented 5.2% (0.55 kg/hm²) and 12.9% (6.16 kg/hm²) decreases in wheat and rice season, respectively. The two chlorine-containing fertilizers both increased significantly the load of the chlorine residual in soil during the rice season but had a reduced trend during the wheat season. Above all, the chlorine residual in soil after the harvest was less than 160 mg/kg, which was under the reported threshold of the chlorine resistance for the rice and wheat. The pH in soil of the UAMF was also not changed significantly, but that of the ammonium chloride decreased by 0.88 units compared with the urea.

ConclusionsTaking into consideration both the yield and environmental benefit in the rice–wheat rotation system, the UAMF should be a promising N fertilizer for replacing urea or ammonium chloride in Taihu Lake region.