Combined application of organic and inorganic fertilizers sustained rice yields and N accumulation and decreased soil-canopy system NH3 emission

Abstract

Excessive inorganic fertilization created various environmental problems, and the combination of organic and inorganic fertilization not only maintains crop production but is also environmentally sustainable. A pot experiment was conducted in Yangzhou, China, to investigate the comprehensive effects of organic fertilization combined with inorganic fertilization on the yield and yield components, nitrogen (N) uptake of different organs, and soil-plant system ammonia (NH₃) emissions of two rice cultivars, taking into account the interception of soil NH₃ emissions by the rice canopy. The treatments included the conventional practice of inorganic N applied by local farmers (INO, 270 kg N ha⁻¹), 30 % reduced INO (70 %-INO, 189 kg N ha⁻¹), and organic fertilizer combined with 70 %-INO (ORG-INO). Compared to 70 %-INO, ORG-INO significantly increased grain yield by 38 %, mainly due to more panicles. Similarly, ORG-INO also significantly promoted N uptake in the two rice cultivars, especially in terms of grain N accumulation, relative to 70 %-INO. The increase in grain N accumulation caused by ORG-INO was mainly due to enhanced post-anthesis N uptake, rather than N remobilization of vegetative organs, which also suggested that organic fertilizer could modify the processes of N retention and release. There was no significant difference in rice yield and N accumulation between INO and ORG-INO treatments, which also indicated that ORG-INO was effective in maintaining grain yield while reducing inorganic fertilizer input. Moreover, ORG-INO significantly reduced soil-plant system NH₃ emissions, while the rice canopy intercepted approximately 30 % of soil NH₃ emissions throughout the entire growing season. In summary, ORG-INO treatment significantly reduced the yield-scaled NH₃ emissions, and the partial substitution of organic fertilizers for inorganic fertilizers should be recommended to promote environmental sustainability while ensuring food security.