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There is still limited information about the influence of different tillage and crop residue management on soil bacterial communities in the paddy field. Therefore, the short-term effects of tillage and incorporated crop residue management on soil properties and bacterial communities in a double-cropping rice system of southern China were studied. The experiment included four tillage treatments: conventional tillage with crop residue incorporation (CT), rotary tillage with crop residue incorporation (RT), no-tillage with crop residue retention (NT), and rotary tillage without crop residue as control (RTO). The results indicated that soil invertase, urease and catalase activities with CT treatment were increased 11.5%, 82.6% and 43.9%, compared with RTO treatment. Meanwhile, the results showed that genetic diversity indices of soil microbial communities increased by application of crop residue treatments, compared to without crop residue treatment. The value of Richness indices and McIntosh indices with CT treatment were increased by 10.8% and 35.4%, compared with RTO treatment. CT and RT treatments increase the abundance of phylum Alphaproteobacteria, Firmicutes and Gammaproteobacteria, compared to RTO treatment. Therefore, the combined application of tillage and crop residue management could significantly increase the abundance of profitable functional bacteria species in the double-cropping paddy field of southern China. [ABSTRACT FROM AUTHOR]

Soil nitrogen (N)‐fixing bacteria community plays an important role in the N cycling process in soil, but there is still limited information about how the soil microbes that drive this process to respond to combined application of tillage and crop residue management under the double‐cropping rice (Oryza sativa L.) paddy field in southern of China. Therefore, the effects of 6‐years short‐term tillage treatment on soil N‐fixing bacteria community under the double‐cropping rice paddy field in southern China were studied by using the polymerase chain reaction‐denaturing gradient gel electrophoresis method. The field experiment included four tillage treatments: conventional tillage with crop residue incorporation (CT), rotary tillage with crop residue incorporation (RT), no‐tillage with crop residue retention (NT), rotary tillage with crop residue removed as control (RTO). The results showed that the diversity index and richness index of cbbLR and nifH genes with CT, RT, and NT treatments were increased, compared with RTO treatment. Compared with RTO treatment, the abundance of cbbLR gene with CT, RT, and NT treatments were increased by 6.54, 4.73, and 2.78 times, respectively. Meanwhile, the abundance of nifH gene with CT, RT, and NT treatments were 5.32, 3.71, and 2.45 times higher than that of RTO treatment. The results also indicated that soil autotrophic Azotobacter and nitrogenase activity with CT and RT treatments were significantly higher (p <.05) than that of RTO treatment. There was an obvious difference in characteristic of soil N‐fixing bacteria community between the application of crop residue and without crop residue input treatments. In summary, the results indicated that the abundance of N‐fixing bacteria community in the double‐cropping rice paddy field increased with conventional tillage and rotary tillage practice. [ABSTRACT FROM AUTHOR]

Carbon (C) plays an important role in the activity and diFversity of soil microbial community, but there is still limited information about how C source utilization soil microbial structure responds to soil organic carbon changes under the double‐cropping rice (Oryza sativa L.) system in southern China's paddy fields. Therefore, the effects of short‐term (5‐year) tillage treatments on characteristics of C source utilization microbial structure in both rhizosphere and non‐rhizosphere soils under double‐cropping were investigated by using metagenome sequencing technology. The experiment included four tillage treatments: conventional tillage with crop residue incorporation (return), rotary tillage with crop residue return, no‐tillage (zero‐tilllage) with crop residue return, and rotary tillage with crop residue removed as control. The results showed that relative abundance of Firmicutes, Alphaproteobacteria and Deltaproteobacteria in both rhizosphere and non‐rhizosphere soils was increased by combined application of tillage with crop residue return practice. Regarding the cluster of orthologous groups of proteins categories, the largest group was 'amino acid transport and metabolism' with 0.223% unigenes, followed by 'general function prediction only' (0.205%), and 'nuclear structure' (0.005%) was the smallest group. And the gene ontology categories with different tillage treatments in following decreasing order: biological process (144,229, 42.4%) > cellular component (104,981, 30.8%) > molecular function (91,284, 26.8%). The principal coordinate analysis indicated that different parts of root zone and tillage treatments were the most and the second most important factors affecting the variation of C source utilization bacteria community, respectively. Therefore, the results showed that combined application of tillage with crop residue return practice significantly increased the C source utilization of soil microorganisms in the double‐cropped rice fields. [ABSTRACT FROM AUTHOR]

This study aimed to determine short-term effects of soil tillage and crop residues on soil quality and grain yield of rice in a double-cropping paddy field of southern China. The experiment included four soil tillage treatments: conventional tillage with crop residues incorporation (CT), rotary tillage with crop residues incorporation (RT), no-tillage with crop residues retention (NT), and rotary tillage with crop residues removed as control (RTO). The results showed that the soil bulk density with RTO treatment were higher than with CT and RT treatments. And the soil EC, aggregate mean weight diameter in both wet and dry sieving with NT and RT treatments were higher than that of RTO treatment. CT and RT treatments had the best soil quality and produced the highest rice yield of average 2016–2018. Removing the crop residues gave the lowest yield and less favourable soil physical and chemical characteristics compared to the application of crop residues treatments. It was found that conventional tillage and rotary tillage with crop residues retention is a feasible management technology for farmers producing rice in the double-cropping paddy field of southern China, resulting in a better soil quality and higher yield than with the conventional farmer practice. [ABSTRACT FROM AUTHOR]

The interval and Bayesian estimation methods are important ones to infer structural resistance design value based on the outcome of the tests in International Standard ISO 2394; 1998, but the results obtained by these two methods are not consistent, which would lead to the confusion for designers to choose the methods. Although the Bayesian estimation method is only adopted in European Standard EN 1990: 2002, being different from the general Bayesian estimation method, it does not set confidence level for inferring, which makes it difficult to judge explicitly the degree of confidence on the results of inference. Moreover, on condition that the coefficient of variation is known when the resistance obeys the normal distribution, the methods for inferring structural resistance design values are not provided in these two standards, which could not meet the practical needs. In order to solve those problems, for the cases that the resistance obeys the normal distribution and log-normal distribution, a new Bayesian estimation method with explicit confidence level was developed for inferring structural resistance design values. Based on the joint posterior distribution of unknown parameters, the proposed method can give a result consistent with that by the interval estimation method. Through comparative analysis, it reveals the reason why the inference results obtained by the Bayesian and the interval estimation methods are different in International standard. On the basis of the interval estimation method, the methods for inferring structural resistance design values with the known coefficient of variation are put forward. The proposed method could help designers to judge the degree of confidence on the results of inference explicitly, which can satisfy the needs of practical inference. [ABSTRACT FROM AUTHOR]

Soil carbon (C) content plays an important role in maintaining or increasing soil quality and soil fertility. However, the impacts of different tillage and crop residue incorporation managements on greenhouse gas (GHG) emissions from paddy fields under the double-cropping rice (Oryza sativa L.) system in southern China still need further study. Therefore, a field experiment was conducted to determine the impacts of different short-term (5-years) tillage and crop residue incorporation managements on soil organic carbon (SOC) content, SOC stock, and GHG emissions from paddy fields under the double-cropping rice system in southern China. The field experiment included four tillage treatments: rotary tillage with all crop residues removed as a control (RTO), conventional tillage with crop residue incorporation (CT), rotary tillage with crop residue incorporation (RT), and no-tillage with crop residue retention (NT). These results indicated that SOC stock in paddy fields with CT, RT, and NT treatments increased by 4.64, 3.60, 3.50 Mg ha−1 and 4.68, 4.21, and 4.04 Mg ha−1 in 2019 and 2020, respectively, compared with RTO treatment. The results showed that early rice and late rice yield with CT treatment increased by 7.22% and 19.99% in 2019 and 6.19% and 6.40% in 2020, respectively, compared with RTO treatment. A two-year (2019–2020) investigation of GHG results indicated that methane emissions from paddy fields with NT treatment were decreased, but nitrous oxide emissions from paddy fields were increased. The lowest mean global warming potential (GWP) and per yield GWP carbon dioxide were found with NT treatment, compared to RT and CT treatments. Therefore, it was a beneficial practice for maintaining SOC stock and decreasing GHG mitigation under the double-cropping rice system in southern China by applying no-tillage with crop residue retention management. [ABSTRACT FROM AUTHOR]

Soil extracellular enzyme plays a vital role in changing soil nitrogen (N) mineralization of rice field. However, the effects of soil extracellular enzyme activities (EEA) and microbial community composition response to N mineralization of rice field under short-term tillage treatment needed to be further explored. In this study, we investigated the impact of short-term (8-year) tillage practices on rhizosphere soil N transformation rate, soil enzyme activities, soil microbial community structure, and the N mineralization function gene abundances in double-cropping rice field in southern China. The experiment consisted of four tillage treatments: rotary tillage with crop straw input (RT), conventional tillage with crop straw input (CT), no-tillage with crop straw retention (NT), and rotary tillage with all crop straw removed as a control (RTO). The results indicated that the rhizosphere soil N transformation rate in paddy field under the NT and RTO treatments was significantly decreased compared to RT and CT treatments. In comparison to the NT and RTO treatments, soil protease, urease, β -glucosaminidase, and arginase activities were significantly improved by the CT treatment, as were abundances of soil sub , npr , and chiA with CT and RT treatments. Moreover, the overall diversity of soil bacterial communities in NT and RTO treatments was significantly lower than that in RT and CT treatments. Soil chitinolytic and bacterial ureolytic communities were also obviously changed under a combination of tillage and crop straw input practices.

Soil autotrophic bacterial communities play a significant role in the soil carbon (C) cycle in paddy fields, but little is known about how rhizosphere soil microorganisms respond to different long-term (35 years) fertilization practices under double rice cropping ecosystems in southern China. Here, we investigated the variation characteristics of rhizosphere soil RubisCO gene cbbL in the double rice ecosystems of in southern China where such fertilization practices are used. For this experiment we set up the following fertilizer regime: without any fertilizer input as a control (CK), inorganic fertilizer (MF), straw returning (RF), and organic and inorganic fertilizer (OM). We found that abundances of cbbL , 16S rRNA genes and RubisCO activity in rhizosphere soil with OM, RF and MF treatments were significantly higher than that of CK treatment. The abundances of cbbL and 16S rRNA genes in rhizosphere soil with OM treatment were 5.46 and 3.64 times higher than that of CK treatment, respectively. Rhizosphere soil RubisCO activity with OM and RF treatments increased by 50.56 and 45.22%, compared to CK treatment. Shannon and Chao1 indices for rhizosphere soil cbbL libraries with RF and OM treatments increased by 44.28, 28.56, 29.60, and 23.13% compared to CK treatment. Rhizosphere soil cbbL sequences with MF, RF and OM treatments mainly belonged to Variovorax paradoxus , uncultured proteobacterium, Ralstonia pickettii , Thermononospora curvata , and Azoarcus sp.KH33C. Meanwhile, cbbL -carrying bacterial composition was obviously influenced by soil bulk density, rhizosphere soil dissolved organic C, soil organic C, and microbial biomass C contents. Fertilizer practices were the principal factor influencing rhizosphere soil cbbL -carrying bacterial communities. These results showed that rhizosphere soil autotrophic bacterial communities were significantly changed under conditions of different long-term fertilization practices Therefore, increasing rhizosphere soil autotrophic bacteria community with crop residue and organic manure practices was found to be beneficial for management of double rice ecosystems in southern China.