Effects of long-term fertilization on integrated fertility and rice yield in yellow paddy soil

【 Objective】 To evaluate the effects of long-term different fertilization treatments on the comprehensive fertility and rice yield of yellow paddy soil in southwest China， and to provide scientific reference for farmland soil fertilization and crop productivity enhancement in southwest China.【Method】The study was based on the long-term fertilization experiment by the Scientific Observing and Experimental Station of Arable Land Conservation and Agricultural Environment（Guizhou）， Ministry of Agriculture and Rural Affairs. The ten fertilization treatments includedno fertilization（CK）， single application of nitrogen fertilizer（N），nitrogen and phosphorus fertilizer（NP），nitrogen and potassium fertilizer （NK），phosphorus and potassium fertilizer（PK），balanced fertilizer（NPK），25% organic fertilizer replacement fertilizer （3/4NP+1/4M），50% organic fertilizer replacement fertilizer（1/2NP+1/2M），single application of organic fertilizer （M），combined application of organic fertilizer and chemical fertilizer（NPK+ M）. The rice yields and top soil properties collected from 2016 to 2020 were measured， and the change trends of soil fertility was assessed using the improved Nemoro index（IFI）. Random forest regression was used to assess the importance of soil property indexes on integrated soil fertility. The stability and sustainability characteristics of rice yield under different fertilization management were assessed based on stability index and sustainability index， and the effect of different fertilizer applications on soil fertility and crop yield was clarified by path analysis.【Result】Long-term different fertilizer managements had obvious effects on integrated fertility（IFI） in yellow paddy soil. The lowest IFI was in the treatment N and the highest in the treatment NPK+ M. The IFI of each treatment with long-term application of organic fertilizer（3/4NP+1/4M， 1/2NP+1/2M， M， NPK+M） were significantly higher than CK and each treatment with chemical fertilizer（N， NP， NK， NPK）（P<0.05，the same below）. Random forest regression analysis showed that soil available phosphorus and soil organic matter content were important influencing factors on soil integrated fertility index， with relative importance of 32.1% and 25.0%， respectively. The results of rice yield showed that the rice yield of partial replacement of chemical fertilizer by organic fertilizer （3/4NP+1/4M and 1/2NP+1/2M）and NPK+M were significantly higher than those of treatments CK， NK and N. Rice yield stability and sustainability were higher in each treatment（3/4NP+1/4M， 1/2NP+1/2M， M， and NPK+M） with organic ferti-lizer application while achieving high yields； rice yields were lower in the CK， N， and NK treatments and yield stability and sustainability were lower. Soil integrated fertility index was closely related to rice yield. The path analysis showed that long-term application of phosphorus fertilizer and organic fertilizer promoted the integrated fertility of yellow paddy soils and increased crop yield ；short-term application of nitrogen fertilizer and phosphorus fertilizer promoted rice yield increase.【Conclusion】 Long-term application of organic fertilizer and phosphorus fertilizer improves soil integrated fertility of yellow paddy soil， and maintain high， stable and sustainable rice grain yield. Available phosphorus and soil organic matter are the most important soil indicators affecting the integrated fertility of yellow paddy soil.