College of Hydrology and Water Resources, Hohai University, Nanjing 210098, PR China.
Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing 210098, PR China.
Sci Total Environ. 2022 Aug 25;836:155706. doi: 10.1016/j.scitotenv.2022.155706. Epub 2022 May 5.
Increasing rice yield is essential for alleviating global food crisis. High soil nutrient level guarantees high rice yields in conventional rice monoculture (RM) systems, but excessive unconsumed nutrients act as pollutants and can even threaten rice growth. The integrated rice-crayfish (IRC) system aims to transfer the excess nutrients from crayfish to paddy fields to improve the comprehensive utilization rate of nutrients and create additional profits, while the responding characteristics of IRC microbial communities in paddy fields and rice yields to the nutrient status remain unclear. Considering the crucial roles of microbiomes in promoting nutrient cycling for crop absorption in rice production progresses, the composition and functional characteristics of soil microbial communities from six IRC farms with variant nutrient statuses in the Yangtze River Delta were surveyed in this study. Compared with RM systems, IRC systems with appropriately improved (p < 0.05) soil quality created favorable nutrient (FN) status accompanied by 15% rice yields increase, while IRC systems with extremely high nutrients (HN) status (p < 0.01) accompanied by 14% rice yields reduction. Soil microbial diversity and network complexity were maintained in FN-IRC systems, but declined in HN-IRC systems, with the Shannon index significantly decreased by 9.2% and network density decreased from 0.135 (in RM) to 0.062. In the FN-IRC systems, the keystone taxa identified by co-occurrence networks displayed inextricably positive correlations with soil nitrification potential (calculated by normalization of amoA gene abundance) and rice yields. While in HN-IRC systems, the large loss of keystone taxa might limit soil nitrogen fixation potential (calculated by normalization of nifH gene abundance), and further rice yields. Our study indicates that soil nutrient management in IRC systems claim attention, and the improvement of nitrogen metabolism is the key to realize agricultural cleaner production.
提高水稻产量对于缓解全球粮食危机至关重要。高土壤养分水平保证了常规水稻单作（RM）系统的高水稻产量，但过量未消耗的养分会成为污染物，甚至会威胁到水稻的生长。稻虾共生（IRC）系统旨在将虾类的多余养分转移到稻田中，以提高养分的综合利用率并创造额外的利润，而 IRC 微生物群落对稻田和水稻产量的养分状况的响应特征仍不清楚。考虑到微生物组在促进水稻生产过程中作物吸收养分循环方面的关键作用，本研究调查了长三角六个具有不同养分状况的 IRC 农场的土壤微生物群落的组成和功能特征。与 RM 系统相比，IRC 系统通过适当改善（p < 0.05）土壤质量，创造了有利的养分（FN）状态，同时水稻产量提高了 15%，而养分极高（HN）状态的 IRC 系统（p < 0.01），水稻产量降低了 14%。FN-IRC 系统中的土壤微生物多样性和网络复杂性得以维持，但 HN-IRC 系统中的土壤微生物多样性和网络复杂性下降，Shannon 指数显著降低了 9.2%，网络密度从 RM 中的 0.135 降低到 0.062。在 FN-IRC 系统中，通过共现网络确定的关键类群与土壤硝化潜力（通过amoA 基因丰度归一化计算）和水稻产量呈正相关。而在 HN-IRC 系统中，大量关键类群的丧失可能会限制土壤固氮潜力（通过 nifH 基因丰度归一化计算），并进一步影响水稻产量。本研究表明，IRC 系统中的土壤养分管理需要引起重视，改善氮代谢是实现农业清洁生产的关键。
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