Persulfate pretreatment facilitates decomposition of maize straw in soils and accumulation of straw residues with high adsorption capacity

Abstract

Because of the complex and recalcitrant structure of straw, large amounts of straw residues accumulate in soils with straw return practice, and pose various adverse impacts. In this study, both laboratory experiments and field demonstration were conducted to investigate the effects of persulfates (PS) pretreatments on structure and properties of maize straw. PS pretreatment of maize straw was developed to facilitate decomposition of returned straw in soils. Persulfates break the aryl C-O bonds of stable lignin units and destroy dense crystalline structure of cellulose units. The former impact was pronounced at high levels of PS. Both impacts were responsible for the accelerated decomposition of maize straw in field soils. The decomposition of maize straw with 0.1% PS pretreatment was increased by 29% (181 d), often superior to the biological-based methods. Interestingly, all straw residues collected in the soils with PS-treated maize straw return after 43 d displayed higher adsorption capacity of the four commonly used herbicides. The adsorption Kd values of herbicides were about 76%–123% higher than those by straw residues collected in the soils with pristine maize straw return. Additionally, all PS pretreatments posed no adverse impacts to both soil bacterial and fungi community. Some of Top Ten bacteria or fungi were stimulated, highlighted by the increases in relative abundances by 4.02%–963%. These results demonstrate that PS pretreatments can serve as an easy and applicable approach to reducing straw residues in soils. Then PS pretreatment may have environmental significance in alleviating accumulation of straw residue in soils and diffusion of pesticides into aquatic systems.