Soil properties and microbial functional attributes drive the response of soil multifunctionality to long-term fertilization management

Abstract

Fertilization is a vital management practice to improve soil fertility and promote agricultural production. However, there is limited knowledge about the interactive effects between soil abiotic and biotic factors and soil multifunctionality after long-term fertilization. There has been little research on determining whether the application of organic fertilizers can improve the functional potential of microorganisms to maintain multifunctional stability. In this study, we integrated soil physicochemical properties, extracellular enzyme activities, bacterial community characteristics, and the abundance of functional genes related to carbon (C) and nitrogen (N) cycling to evaluate the mechanism of soil functional potential response to 13 years of fertilization management. Four treatments were compared, including no fertilizer (CK), conventional fertilization (CF), formulated fertilization by soil testing (SF), SF with organic fertilizer (SFO). The addition of organic fertilizer enhanced the soil electrical conductivity, N-cycling enzyme activities, contents of macroaggregate and associated C, and soil nutrients, while decreasing the content of microaggregates compared with other treatments. The co-application of chemical and organic fertilizer led to significant increases in soil multifunctionality and the bacterial Shannon index compared with the CK and CF treatments. Soil abiotic factors are the key predictors for shaping soil multifunctionality. The addition of organic fertilizer could increase the abundance of functional genes related to C- and N-cycling mediated by the contents of nutrients and the aggregates associated with nutrients. Additionally, treatment with organic fertilizer can mitigate the decrease in genes for C-cycling function caused by the long-term application of chemical fertilizer (SF). In addition, the structural equation models revealed that the fertilization positively affected soil multifunctionality indirectly by changing the bacterial diversity and community composition, as well as the functional potential related to N-cycling. Overall, soil properties and microbial functional attributes jointly drive the response of soil multifunctionality to long-term fertilization management. These results suggest that the combination of organic and chemical fertilizer is worth popularizing to improve multifunctionality and its stability to maintain agricultural sustainability.