Soil bacterial community composition in rice-turtle coculture systems with different planting years

Abstract

The rice-turtle coculture system is the most special rice-fish integrated farming system. In this study, we selected four paddy fields, including a rice monoculture paddy and three rice-turtle paddies with different planting years, to investigate the soil bacterial community composition with Illumina MiSeq sequencing technology. The results indicated that the contents of soil available nitrogen (AN), soil available phosphorus (AP) and soil organic matter (OM) in 9th year of rice-turtle paddy (RT9) were increased by 5.40%, 51.11% and 23.33% compared with rice monoculture paddy (CK), respectively. Significant differences of Acidobacteria, Desulfobacteria, Crenarchaeota were observed among the different rice farming systems. The relative abundance of Methylomonadaceae, Methylococcaceae and Methylophilaceae in RT9 was significantly higher than that in other treatments. RT9 had significantly lower relative abundance of Acidobacteria, but significantly higher relative abundance of Proteobacteria than other treatments. Redundancy analysis showed that soil AN and AP contents were the major factors influencing the abundance of the dominant microbes, wherein Methylomonadaceae, Methylococcaceae and Methylophilaceae were positively correlated with OM. The findings revealed the rice-turtle coculture system in the 9th year had higher soil nutrients and soil bacterial diversity, but there was also a risk of increasing methane emissions.

Effects of Rice–Frog Co-Cropping on the Soil Microbial Community Structure in Reclaimed Paddy Fields

“…Additionally, the feed for the frogs is also rich in nutrients, and this uneaten feed could also permeate the soil and increase its content of N. However, there was no significant difference in the content of AN among the three groups at the stage of rice maturity. This result is inconsistent with the results of some other studies, which indicated that rice–aquatic animal co-culture could increase the content of AN in this soil [ 31 , 34 , 37 ]. This could be due to frogs excreting nitrogen as urea or ammonia depending on their environment.…”

“…In this study, except for the high-density rice–frog co-cropping group (SG), the soil AP did not significantly increase in the rice maturity period compared with that before reclamation of the field. This is inconsistent with some previous studies in which the rice–aquatic animal co-culture mode significantly increased the content of AP in the soil [ 36 , 37 , 47 ]. This could be owing to the poor soil fertility and weak biological conditions of the reclaimed fields in this study.…”

“…The contents of SOM and AK in the soil with the high-density rice–frog co-cropping treatment (SG) were significantly higher than those in the soil with the rice monocropping treatment (SF), and the contents of SOM and soil AK increased with the increased density of the frogs in the paddy field. The results were consistent with those of Yi et al [ 34 ] and Wang et al [ 37 ], who showed that the content of AK increased significantly increased in the rice–frog co-cropping group, and the content of SOM increased in the rice–turtle co-cropping group, respectively, when compared with the rice mono-cropping group. In this study, except for the high-density rice–frog co-cropping group (SG), the soil AP did not significantly increase in the rice maturity period compared with that before reclamation of the field.…”

“…Several studies have demonstrated that a soil's chemical properties can affect the bacterial community composition of a field [31,34,59,60]. In this study, the RDA between the soil chemical properties and soil microorganisms revealed that the contents of TN, AN, AK, SOM, and AP in the soil were the primary environmental factors that affected the distribution of bacterial communities, which is consistent with the results of several previous studies [31,36,37,61]. The results of this study reveal that the contents of N, AK, SOM, and AP are positively correlated with the abundances of Acidobacteriota, Actinobacteriota, Chloroflexi, and Planctomycetota, but negatively correlated with the abundance of Firmicutes.…”

“…Therefore, soil microbial communities can be used as indicators to track changes in various land management practices, such as those in restoration outcomes [ 30 , 31 ] or evaluations of agricultural management practices [ 32 ]. It has been found with different aquaculture species that an integrated rice-farming model can increase the populations of microorganisms in the soil, as well as the diversity of their communities, and improve the availability of nutrients in the soil [ 13 , 31 , 33 , 34 , 35 , 36 , 37 ].…”