Improvement of straw decomposition and rice growth through co-application of straw-decomposing inoculants and ammonium nitrogen fertilizer

Abstract

Abstract Background The growth of rice is reduced by the slow decomposition of accumulated straw, which competes with rice for soil nitrogen nutrient. In recent year, straw-decomposing inoculants (SDIs) that can accelerate straw decomposition and ammonium nitrogen (N) fertilizer that can quickly generate available N is increasingly adopted in China. However, it is still unknown whether the N demand of straw decomposition and crop growth can be simultaneously met through the co-application of SDIs and ammonium N fertilizer. Results In this study, we investigated the effect of the co-application of SDIs and ammonium bicarbonate on decomposition rate of wheat straw, rice growth and rice yield over two consecutive years in rice-wheat rotation system. Compound fertilizer (A0) was used as control. The ratios of ammonium bicarbonate addition were 20% (A2), 30% (A3) and 40% (A4), respectively, without SDIs or with SDIs (IA2, IA3, IA4). Our results revealed that without SDIs, compared with A0, straw decomposition rate, rice growth and yield were improved under A2; However, under A3, rice yield was decreased due to the slow decomposition rate of straw and limited growth of rice during late growth stage. Combining SDIs and N fertilizer increased straw decomposition rate, rice growth rate and yield more than that of N fertilizer alone, especially under IA3. Compared with A0, straw decomposition rate, tiller number, aboveground biomass, leaf area index, root length, and nitrogen use efficiency were significantly increased by 16%, 8%, 27%, 12%, 17%, and 15% under IA3. Consequently, the average rice yield of IA3 was increased to 10,856 kg/ha, which was 13% and 9% higher, respectively, than of A0 and A2. Conclusion Our results indicated that ammonium bicarbonate application alone carried a risk of nutrient deficiency during late growth stage and yield decline. Therefore, the co-application of SDIs and 30% ammonium N fertilizer substitution can be a favorable practice to simultaneously accelerate straw decomposition and increase rice crop growth.