Influence of 20–Year Organic and Inorganic Fertilization on Organic Carbon Accumulation and Microbial Community Structure of Aggregates in an Intensively Cultivated Sandy Loam Soil

Abstract

To evaluate the long–term effect of compost (CM) and inorganic fertilizer (NPK) application on microbial community structure and organic carbon (OC) accumulation at aggregate scale, soils from plots amended with CM, NPK and no fertilizer (control) for 20 years (1989–2009) were collected. Soil was separated into large macroaggregate (>2,000 μm), small macroaggregate (250–2,000 μm), microaggregate (53–250 μm), silt (2–53 μm) and clay fraction (<2 μm) by wet-sieving, and their OC concentration and phospholipid fatty acids (PLFA) were measured. The 20-year application of compost significantly (P<0.05) increased OC by 123–134% and accelerated the formation of macroaggregates, but decreased soil oxygen diffusion coefficient. NPK mainly increased OC in macroaggregates and displayed weaker influence on aggregation. Bacteria distributed in all aggregates, while fungi and actinobacteria were mainly in macroaggregates and microaggregates. The ratio of monounsaturated to branched (M/B) PLFAs, as an indicator for the ratio of aerobic to anaerobic microorganisms, increased inversely with aggregate size. Both NPK and especially CM significantly (P<0.05) decreased M/B ratios in all aggregates except the silt fraction compared with the control. The increased organic C in aggregates significantly (P<0.05) negatively correlated with M/B ratios under CM and NPK. Our study suggested that more efficient OC accumulations in aggregates under CM–treated than under NPK–treated soil was not only due to a more effective decrease of actinobacteria, but also a decrease of monounsaturated PLFAs and an increase of branched PLFAs. Aggregations under CM appear to alter micro-habitats to those more suitable for anaerobes, which in turn boosts OC accumulation.

Aggregate size and their disruption affect 14C-labeled glucose mineralization and priming effect

“…Assuming that the fungal population metabolizes the substrate more efficiently than bacteria (Otten et al, 2001;Keiblinger et al, 2010), we suppose that crushing decreased CUE by altering the soil microbial community structure. The decreased CUE after crushing was mainly pronounced in macroaggregates where the fungi presumably occur (Guggenberger et al, 1999;Zhang et al, 2014). Similarly, we also found that aggregate crushing did not affect the CUE (%0.45) in microaggregates in this study (Supplementary Table 1).…”

“…5). This result may be partly explained by the decreased role of fungi due to disruption of fungal mycelia by crushing, assuming that fungi are important PE drivers (Fontaine et al, 2011) and that fungi occur mainly in macroaggregates (Guggenberger et al, 1999;Zhang et al, 2014). In addition, the bacteria may switch from decomposing hardly utilizable substrates such as SOM to metabolizing the added glucose (preferential substrate utilization) (Paterson et al, 2007;Kuzyakov, 2010).…”

Effects of Continuous Tomato Monoculture on Soil Microbial Properties and Enzyme Activities in a Solar Greenhouse

“…Over the past several years, many researchers have attempted to determine how to eliminate these obstacles through improving cultivation and management methods. Most research has focused on screening superior varieties to alleviate pests and disease, introducing grafting techniques to enhance plant resistance, applying organic fertilizer to improve soil quality, or selecting alternative rotations to balance soil nutrition [18][19][20]. However, the changes in soil quality due to continuous monoculture over several years or crops have been rarely reported.…”

Soil Microbial Community Structure and Diversity in Cut Flower Cultures Under Conventional and Ecological Management

“…Changes in bacterial communities may also be due to the effects of organic fertilizer on soil structure. Zhang et al (2014) showed that long-term applications of organic fertilizers accelerated the formation of soil aggregates, while simultaneously decreasing the oxygen diffusion coefficient, making microhabitats more suitable for anaerobes. The soil water content may also be driving shifts in the genetic structure and diversity of the bacterial communities under CM and EM.…”