Abstract
The effects of soil type and organic material quality on the microbial biomass and functional diversity of cropland soils were studied in a transplant experiment in the same climate during a 1-year field experiment. Six organic materials (WS: wheat straw, CS: corn straw, WR: wheat root, CR: corn root, PM: pig manure, CM: cattle manure), and three contrasting soils (Ferralic Cambisol, Calcaric Cambisol and Luvic Phaeozem) were chosen. At two time points (at the end of the 1st and 12th months), soil microbial biomass carbon (C) and nitrogen (N) (MBC and MBN) and Biolog Ecoplate substrate use patterns were determined, and the average well color development and the microbial functional diversity indices (Shannon, Simpson and McIntosh indices) were calculated. Organic material quality explained 29.5–50.9% of the variance in MBC and MBN when compared with the minor role of soil type (1.4–9.3%) at the end of the 1st and 12th months, and C/N ratio and total N of organic material were the main parameters. Soil properties, e.g., organic C and clay content were the predominant influence on microbial functional diversity in particular at the end of the 12th month (61.8–82.8% of the variance explained). The treatments of WS and CS significantly improved the MBC and microbial functional diversity indices over the control in the three soils in both sampling periods (P < 0.05). These results suggest that the application of crop straw is a long-term effective measure to increase microbial biomass, and can further induce the changes of soil properties to regulate soil microbial community.
Highlights
Soil microorganisms drive the turnover of exogenous organic materials into soil organic matter [1]
At the end of the 1st month, the contributions of soil type and organic material type were significant in explaining the variance in MBC and MBN, and explained 6.9 and 43.6% of the variance in MBC, as well as 9.3 and 50.9% of the variance in MBN, respectively (P < 0.05; Table 3)
The amount of available C and N sources decreased and further entered the environment, e.g., as C and N gaseous emissions, dissolved organic C and nitrate leaching under the high precipitation in the experimental subtropical region, especially in the manure amendment treatments; large amounts of decomposable and passive decomposable C sources and nutrients were activated by microbial metabolism, and these activated C sources and nutrients can be lost
Summary
Soil microorganisms drive the turnover of exogenous organic materials into soil organic matter [1]. In China, large amounts of agricultural byproducts are produced because high agricultural productivity is being pursued to meet the food demands of the huge population.
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