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Soil cellulose plays a vital role in keeping or increasing carbon (C) cycling and fertility of rice fields. There is a close relation between soil fulvic acid (FA), humin (HM) fractions, and GH48, cbhI genes. However, the effects of different tillage practices on soil humus C content composition, GH48, and cbhI genes abundances in different soil particle‐size fractions of double‐cropping rice fields still need to be further investigated. Therefore, the impacts of different short‐term tillage practices on soil GH48 and cbhI genes abundances in double‐cropping rice fields were conducted. This experiment set up different tillage practices: rotary tillage with crop straw removed as a control (RTO), conventional tillage with crop straw in put (CT), rotary tillage with crop straw in put (RT), and no‐tillage with crop straw retain (NT). The result indicated that the distribution of soil humus, and GH48, cbhI genes abundances were significantly enhanced under combined applied with tillage and crop straw incorporation conditions. Soil FA, HM, and humic acid (HA) C content in 2000–50 μm and >2000 μm fractions with RTO treatment were significantly lower than that of CT, RT, and NT treatments. This result showed that oalkyl and alkyl of HA and FA in 2000–200, 200–50, 50–2, and 2–0.1 μm fractions with CT, RT, NT, and RTO treatments were lower than that of >2000 μm fraction. There was lower ARO% and more AL% of FA and HA in these fractions under the same tillage condition. The result showed that GH48 and cbhI genes abundances in these fractions with CT, RT, and NT treatments were significantly higher than that of RTO treatment. There had significantly positively correlated with GH48, cbhI genes abundances, and soil HA, FA, HM C contents, o‐alkyl C, and AL% of FA. Therefore, it was positively practiced for increasing GH48 and cbhI genes abundances in the double‐cropping rice fields by applying with tillage and crop straw incorporation. [ABSTRACT FROM AUTHOR]

Soil extracellular enzyme activity plays an important role in regulating the process of nitrogen (N) mineralization in the paddy field. However, there is still limited information about how rhizosphere N mineralization and its extracellular enzyme activities respond to different tillage treatments in a double‐cropping rice paddy fields of southern China. Therefore, the effects of 6‐year (short‐term) tillage management on rhizosphere soil acid hydrolysable N and its fractions, N mineralization, and its extracellular enzyme activities in a double‐cropping rice paddy fields of southern China were studied and reported in this article. 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), and rotary tillage with crop residue removed as a control (RTO). The results showed that rhizosphere soil total acid hydrolysable N and its fractions with CT, RT and NT treatments were higher than those with RTO treatment. Compared to RTO treatment, the rhizosphere soil total acid hydrolysable N content with CT and RT treatments was increased by 19.17% and 17.74%, respectively. Compared to RTO treatment, the rhizosphere soil aerobic and anaerobic N mineralization rates with CT and RT treatments were increased by 100.00% and 80.65%, and 43.02% and 33.72%, respectively. Rhizosphere soil extracellular enzyme activities with CT and RT treatments were higher than those with NT and RTO treatments. There was a positive correlation between rhizosphere soil amino sugar N, amino acid N, total acid hydrolysable N contents, L‐glutaminase activity and N mineralization rate. The principal component analysis results indicated that rhizosphere soil organic carbon, amino sugar N, amino acid N and total acid hydrolysable N contents, soil β‐glucosaminidase, β‐glucosidase and L‐glutaminase activities were the main factors affecting rhizosphere soil aerobic and anaerobic N mineralization rates. As a result, rhizosphere soil acid hydrolysable N and its fractions, N mineralization, and its extracellular enzyme activities were significantly increased under the combined application of conventional tillage and rotary tillage with the crop residue incorporation condition. [ABSTRACT FROM AUTHOR]

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]

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]

Increasing soil carbon (C) sequestration in paddy field and improving rice nitrogen use efficiency (NUE) are vital for sustainable agriculture and environmental protection. It was a benefit practice for achieving these goals by taken rice straw and organic manure managements. However, there is still need to further investigate the effects of different long-term fertilizer managements on soil C sequestration and NUE under the double-cropping rice system in southern of China. Therefore, the effects of different long-term (36-years) fertilizer practices on soil C sequestration and NUE under the double-cropping rice system in southern of China were investigated in the present paper. The field experiment was included four different fertilizer treatments: chemical fertilizer alone (MF), rice straw residue and chemical fertilizer (RF), 30% organic manure and 70% chemical fertilizer (OM), and without fertilizer input as a control (CK). This result indicated that soil C content at plough layer in paddy field with RF and OM treatments were increased, compared with MF and CK treatments. Besides input C directly into paddy field, soil original organic C accumulation with RF and OM treatments were increased by 1.54% and 3.01%, compared with MF treatment. This result indicated that soil TOC content increase rate and annual topsoil organic C sequestration rate in paddy field with RF and OM treatments increased by 55.56%, 88.89% and 48.05%, 76.62%, compared with MF treatment, respectively. Compared with MF treatment, NUE with RF and OM treatments increased by 10.43% and 22.61%, respectively, mainly due to increasing soil organic C. Grain yield of double-cropping rice with RF and OM treatments increased by 1009.5 and 1166.5 kg ha−1, compared with MF treatment, respectively. This result indicated that there was significantly correlation between NUE/NUE NPK and TOC content with RF and OM treatments, at early rice and late rice growth seasons. Therefore, it was benefit practice for increasing soil carbon sequestration and improving rice NUE in the double-cropping rice system with long-term application of rice straw and organic manure managements. • Soil C contents were increased at plough layer in paddy field with RF and OM treatments. • Soil original organic C accumulation with RF and OM treatments were also increased. • Rice nitrogen use efficiency with rice straw and organic manure managements were increased. [ABSTRACT FROM AUTHOR]