Abstract
Ecological stoichiometry is an important indicator presenting multiple elements balance in agro-ecosystems. However, information on microbial communities and nutrient stoichiometry in soil aggregate fractions under different croplands (rice, maize, and soybean fields) remains limited. Thus, this study investigated water-stable aggregate structure and their internal nutrient stoichiometry under different croplands and ascertain their interaction mechanism with microbial communities. The results showed that no significant difference on the carbon-to-nitrogen ratio (C:N) in soil aggregate fractions was observed, while the carbon-to-phosphorus ratio (C:P) and the nitrogen-to-phosphorus ratio (N:P) were ranked as rice field > maize field > soybean field, and were higher in mega-aggregates (ME, > 1 mm). General fatty acid methyl ester (FAME), Gram-positive bacteria (G+), and Gram-negative bacteria (G−) were predominant microbial communities in all croplands and tented to condense into coarse-aggregates. Redundancy analysis (RDA) demonstrated that N:P ratio was primary environmental controls on the distribution of soil microorganisms. In the Sanjiang Plain, N was the nutrient element limiting agro-ecosystem productivity, and rice cultivation is expected to improve the N-limited nutrient status.
Highlights
Soil carbon (C), as an important soil component, greatly influences soil structure, fertility, and water-holding capacity, presenting a critical effect on the function of agro-ecosystems (Liu et al 2017; Liu et al 2018)
mean weight diameter (MWD) and geometric mean diameter (GMD) were slightly higher in rice field compared to maize field, but were significantly higher compared to soybean field
Soil nutrient content and stoichiometry Total organic carbon (TOC), Total nitrogen (TN), and total phosphorus (TP) levels showed a significant difference related to soil aggregate fractions under different croplands
Summary
Soil carbon (C), as an important soil component, greatly influences soil structure, fertility, and water-holding capacity, presenting a critical effect on the function of agro-ecosystems (Liu et al 2017; Liu et al 2018). Different croplands are closely related to biomass production and biogeochemical cycles (Zhang et al 2019). Difference in water incubation of cultivated fields (rice field: flooding stress; maize and soybean fields: drought stress) and source sink of nutrients (fertilization and crop harvesting) among croplands is considered as main reasons that affect soil nutrient content and stoichiometry (Ahmad et al 2017). Wang et al (2014) demonstrated that the more flooded soils have more fine texture because fine practices have more time to sediment, making that a decrease in C, N, and P (2020) 9:33 release. Gao et al (2014) proved that plant type and management practices were closely related to soil C accumulation and nutrient dynamics. The coupling mechanism among C, N, and P across different croplands is still somewhat uncertain
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