Abstract
Cultivation patterns can cause soil structure alteration. However, few studies have clarified the influence of cultivation pattern and soil depth on soil. The purpose of this experiment was to study the community characteristics of soil microorganisms in the 0–10 cm and 10–20 cm layers beneath paddy fields under organic and conventional cultivation patterns, and reveal the response mechanism of microbial community to cultivation patterns through the correlation analysis of soil nutrient content, enzyme activity and microbial dominant phyla, so as to provide a theoretical basis for high-yield rice cultivation from the perspective of microorganisms. In this study, four types of soil organic cultivation topsoil (OF_S), organic cultivation undersoil (OF_X), conventional cultivation topsoil (CF_S) and conventional cultivation undersoil (CF_X) in paddy fields were collected for nutrient and enzyme activity determination, and composition spectrum analysis of soil microbial community diversity was performed using a high-throughput sequencing platform. The results revealed that organic cultivation increased the contents of alkali-hydrolyzable nitrogen, available phosphorus, available potassium and organic substances in both topsoil and undersoil as well as sucrase and urease activity in the undersoil. α diversity indicated that bacterial abundance in both topsoil and undersoil was organic > conventional cultivation; the microbial diversity index in the undersoil under organic cultivation technique was greater than that of conventional cultivation. A Venn diagram revealed that there was considerable difference in species between topsoil and undersoil under organic and conventional cultivation patterns. The composition of the community structure indicated that Proteobacteria, Acidobacteria, Chloroflexi and Bacteroidetes were the dominant phyla of bacterial communities in paddy fields. Ascomycota and Basidiomycota were the dominant phyla of the fungal community. Cluster analysis results indicated that soil depth of both patterns produced apparent clustering effects on microorganisms. Correlation analysis revealed that contents of various soil nutrients and enzyme activities affected the relative abundance of the dominant bacteria and fungi in varying degrees. Alkali-hydrolyzable nitrogen, available potassium and organic matters were significant factors affecting the dominant phyla of soil. The present study demonstrated that compared with conventional cultivation, organic cultivation improved soil physicochemical property, enhanced soil enzyme activity, and altered soil microbial diversity and bacterial abundance. Soil nutrients, enzyme activity and the microbial community of paddy fields interacted with each other and affected the soil structure together.
Highlights
As one of the vital models for sustainable development of agriculture, organic farming can improve the soil physicochemical property, and diversify soil microorganisms and maintain the stability of the ecosystem [1]
The findings indicated that the topsoil of paddy fields had a higher quantity of microorganisms under both cultivation methods, and the decrease of the microbial abundance of the organic cultivation was smaller with the increase of soil depth
The findings demonstrated that soil enzymes directly reflect the nutrient contents in soil, the soil nutrient contents would affect the number of microorganisms, and enzymes secreted by microorganisms would be reflected at the level of soil enzymes
Summary
As one of the vital models for sustainable development of agriculture, organic farming can improve the soil physicochemical property, and diversify soil microorganisms and maintain the stability of the ecosystem [1]. The exploration on the differences in soil microbial community characteristics between organic and conventional cultivation patterns can provide a theoretical basis for sustainable paddy farming. As the high-throughput sequencing technology advances, numerous studies have been conducted on changes in soil microorganisms in paddy fields under organic cultivation pattern at home and abroad. Owing to the high heterogeneity of soil, different soil environments will affect the abundance of microorganisms [6], and it has been widely recognized that microbial biomass carbon decreases significantly with the increase of soil depth [7,8,9]. Some studies have revealed that with the increase of soil depth, the interaction network between microorganisms turns more intricate, and the interaction between bacteria and fungi communities converts from cooperation into competition [10,11]. Others believe that the soil microbial community in paddy fields has a high adaptive capacity to the gradients of soil depth, and the interaction between microbial communities is stable [12]
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