Responses of Microbial Nutrient Acquisition to Depth of Tillage and Incorporation of Straw in a Chinese Mollisol

Naiwen Zhang,Jun Yan,Xu Chen,Xinchun Lu,Xiaozeng Han,Lei Yan,Wenxiu Zou

doi:10.3389/fenvs.2021.737075

Abstract

Tillage and straw incorporation are important agricultural practices that can break the plow layer and improve Mollisol fertility. The effect of these practices on the limitation of resources for soil microorganisms, however, is unclear. We established a field experiment in 2018 and collection of soil samples in 2020 to study the acquisition of resources by microbes in a Mollisol region in northeastern China. Four treatments were studied: conventional tillage (CT), straw incorporation with conventional tillage (SCT), subsoil tillage (ST) and straw incorporation with subsoil tillage (SST). The limitation of resources for soil microorganisms was assessed using models of extracellular enzymatic stoichiometry. The soil microbes were generally colimited by C and P but not N. The degree of limitation, however, varied among the treatments. SCT and SST alleviated microbial P limitation in the 0–15 and 15–35 cm layers, respectively, but ST did not significantly affect P limitation relative to CT. Interestingly, N-resource contents were strongly correlated with indicators of C and P limitation. A random forest analysis found that the contents of available N and total dissolved N were the most important factors for microbial C and P limitation, respectively. Straw incorporation alleviated microbial P limitation but did not eliminate P limitation and deep tillage aggravate microbial C limitation. We suggest that N fertilization may be reduced due to the N-rich characteristics of the Mollisols in northeastern China.

Highlights

Microbes play a key role in the decomposition of organic matter and the release of nutrients (Daniela et al, 2011; Leininger et al, 2006)
We did find a significantly positive negative relationship between dissolved organic C (DOC) with BG activity in the current study (Table 2) and the DOC contents were significantly higher in the 0–15 cm soil layer and in the 15–35 cm soil layer of the Straw incorporation with subsoil tillage (SST) compared with Subsoil tillage (ST) treatment, it can be assumed that downward transport DOC is relatively high
We investigated the changes in microbial resource limitation by tillage and straw management using enzymatic stoichiometry in a Mollisol in northeastern China

Summary

Introduction

Microbes play a key role in the decomposition of organic matter and the release of nutrients (Daniela et al, 2011; Leininger et al, 2006). Straw incorporation has been widely used to increase soil fertility, with good results (Mahdi et al, 2005), but most studies have focused on the effect of straw mulching or mixing straw with the topsoil (Kahlon et al, 2013; Tao et al, 2015) These strategies of tillage management can increase the content of soil organic C (SOC) of the surface soil and reduce soil disturbance (Choudhury et al, 2014) but are not conducive to improving the structure of deep soil, enhancing the use efficiency of residues or accumulating SOC (Liu et al, 2021). Straw incorporation with deep tillage into the field provide a favorable environment for accelerating the secretion of extracellular enzymes and lead to changes in the contents of soil nutrients (Heinze et al, 2010; Kabiri et al, 2016)

Methods

Results

Discussion

Conclusion