Microbial keystone taxa drive crop productivity through shifting aboveground-belowground mineral element flows.

Unbalanced fertilization of nutritional elements is a potential threat to environmental quality and agricultural productivity in acid soil. Harnessing keystone taxa in soil microbiome represents a promising strategy to enhance crop productivity as well as reducing the adverse environmental effects of fertilizers, with the goal of agricultural sustainability. However, there is a lack of information on which and how soil microbial keystone taxa contribute to sustainable crop productivity in acid soil. Here, we examined soil microbial communities (including bacteria, fungi, and archaea) and soil nutrients, and the mineral nutrition and yield of maize subjected to different inorganic and organic fertilization treatments over 35 years in acid soil. The application of organic fertilizer alone or in combination with inorganic fertilizers sustained high maize yield when compared with the other fertilization treatments. Microbial abundances and community structures rather than their alpha diversities explained the main variation in maize yield among different treatments. Sixteen soil keystone taxa (a fungal operational taxonomic unit and 15 bacterial operational taxonomic units) were identified from the microbial co-occurrence network. Among them, five keystone taxa (in Hypocreales, Bryobacter, Solirubrobacterales, Thermomicrobiales, and Roseiflexaceae) contributed to high maize yield through increasing phosphorus flow and inhibiting toxic aluminum and manganese flow from soils to plants. However, the remaining eleven keystone taxa (in Conexibacter, Acidothermus, Ktedonobacteraceae, Deltaproteobacteria, Actinobacteria, Elsterales, Ktedonobacterales, and WPS-2) exerted the opposite effects. As a result, maize productivity varied among different fertilization treatments because of the altered maize mineral element flows by microbial keystone taxa. We conclude that microbial keystone taxa drive crop productivity through shifting aboveground-belowground mineral element flows in acid soil. This study highlights the importance of microbial keystone taxa for sustainable crop productivity in acid soil and provides deep insights into the relationships between soil microbial keystone taxa, crop mineral nutrition, and productivity.

Balanced fertilization over four decades has sustained soil microbial communities and improved soil fertility and rice productivity in red paddy soil.

The influence of long-term fertilization on soil microbial communities is critical for revealing the association between belowground microbial flora and aboveground crop productivity-a relationship of great importance to food security, environmental protection, and ecosystem functions. Here, we examined shifts in soil chemical properties, microbial communities, and the nutrient uptake and yield of rice subjected to different chemical and organic fertilization treatments over a 40-year period in red paddy soil. Ten different treatments were used: a control without fertilizer, and applications of nitrogen (N), phosphorus (P), potassium (K), NP, NK, PK, NPK, double NPK, or NPK plus manure. Compared with the effects of withholding one or two nutrients (N, P, or K), the balanced application of chemical NPK and organic fertilizers markedly improved soil nutrient status and rice yield. This improvement of soil fertility and rice yield was not associated with bacterial, archaeal, or fungal alpha diversities. The bacterial abundance and community structure and archaeal abundance effectively explained the variation in rice yield, whereas those of fungi did not. The community structure of bacteria and archaea, but not that of fungi, was correlated with soil properties. Among various soil properties, P was the key factor influencing rice yield and soil microbial communities because of the extremely low content of soil available P. Seven keystones at the operational taxonomic unit level were identified: four archaea (belonging to Thermoplasmata, Methanosaeta, Bathyarchaeia, and Nitrososphaeraceae) and three bacteria (in Desulfobacteraceae and Acidobacteriales). These keystones, which were mainly related to soil C and N transformation and pH, may work cooperatively to influence rice yield by regulating soil fertility. Our results collectively suggest that four decades of balanced fertilization has sustained the bacterial and archaeal abundances, bacterial community structure, and keystones, which potentially contribute to soil fertility and rice yield in red paddy soil.

[Basic soil productivity in the double rice cropping system under long-term fertilization regimes in the Poyang Lake region, China]. / 鄱阳湖流域长期施肥下双季稻田的土壤基础地力.

We aimed to explore changes in basic soil productivity (BSP) under different fertilization regimes in the Poyang Lake region, Jiangxi Province, China. Soil samples were collected from a long-term fertilization experiment (since 1981) that included treatments of no fertilization (CK), chemical fertilization (NPK), and combined chemical and organic fertilization (NPKM). Then, a three-year pot experiment (from 2012 to 2014) with double rice cropping was conducted with two different fertilization regimes (no fertilization, F0; fertilization, F1) using CK, NPK and NPKM soils. Grain yield and BSP were analyzed among soils with different fertilization regimes to identify the key factors driving changes in BSP. Results showed that grain yields in NPKM soil were higher than in NPK and CK soils regardless of fertilization in the pot experiment. Under the F0 condition, annual grain yields of NPKM soil were 37.7%-143.9% and 20.8%-66.7% higher than CK and NPK soils, respectively. The BSP values of CK, NPK and NPKM soils in three years were 41.8%-53.1%, 45.2%-62.6% and 59.1%-88.1%, respectively. NPKM soil had significantly higher BSP than NPK and CK soils. Furthermore, there were significant positive correlations between soil organic matter and BSP as well as between organic carbon balance and BSP. These results suggested that long-term application of chemical and organic fertilizers could improve BSP in the double rice cropping system of the Poyang Lake region. In addition, soil organic matter and organic carbon balance are important factors for improving BSP in this region.