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Inversion tillage and organic fertilizer application can break the plow pan and improve soil quality. However, the effects of combining these practices on the soil microbial resource limitation and maize yield in Haplic Chernozem are unclear. In this research, a field experiment was established in 2018, and soil samples were collected in 2021 in Longjiang County in Northeast China, which is a Haplic Chernozem region. Four treatments comprising conventional tillage (T15), conventional tillage with organic fertilizer (T15+M), inversion tillage (T35), and inversion tillage with organic fertilizer (T35+M) were randomly arranged with four replications. Compared with T15 and T15+M treatments, soil bulk density significantly decreased by 11.1–16.3% in the 15–35 cm layer under T35 and T35+M treatments, accompanied by the improvement in soil pore structure (e.g., soil porosity, circularity, and Euler number). T15+M treatment significantly increased soil organic carbon and soil nutrient contents by 11.1–16.3% and 3.9–24.5% in the 0–15 cm layer compared with other treatments. However, soil organic carbon, total nitrogen, available phosphorus content, microbial biomass, and enzymatic activities reached the maximum values in the 0–35 cm layer under T35+M treatment. In addition, T35+M treatment had the highest maize yield and sustainable yield index. Extracellular enzymatic stoichiometry suggested that soil microorganisms are generally co-limited by carbon and phosphorus in Haplic Chernozem. However, T35+M treatment significantly reduced soil microbial resource limitation, which was one important factor impacting maize yield and sustainability. Random-forest and partial least-squares path modeling showed that T35+M treatment could reduce soil microbial resource limitation and increase the stability and sustainability of the maize yield by improving soil available nutrients, microbial biomass, and pore structure. Therefore, the incorporation of inversion tillage and organic fertilizer is a suitable soil management practice in view of increasing soil quality and crop yields in a Haplic Chernozem region. [ABSTRACT FROM AUTHOR]

We examined the effects of fertile soil layer construction technology on soil fertility and maize yield with a 3-year field experiment in Albic soil in Fujin, Heilongjiang Province. There were five treatments, including con¬ventional tillage (T15, without organic matter return) and fertile soil layer construction methods [deep tillage (0¬35 cm) with straw return, T35+S; deep tillage with organic manure, T35+M; deep tillage with straw and organic manure return, T35+S+M; deep tillage with straw, organic manure return and chemical fertilizer, T35+S+M+F]. The results showed that: 1) compared with the T15 treatment, maize yield was significantly increased by 15.4% - 50.9% under fertile layer construction treatments. 2) There was no significant difference of soil pH among all treat¬ments in the first two years, but fertile soil layer construction treatments significantly increased soil pH of topsoil (0-15 cm soil layer) in the third year. The pH of subsoil (15 - 35 cm soil layer) significantly increased under T35+S+M+F, T35+S + M, and T35+M treatments, while no significant difference was observed for T35 + S treat¬ment, compared with T15 treatment. 3) The fertile soil layer construction treatments could improve the nutrient contents of the topsoil and subsoil layer, especially in the subsoil layer, with the contents of organic matter, total nitrogen, available phosphorus, alkali-hydrolyzed nitrogen and available potassium being increased by 3.2% - 46.6%, 9.1%-51.8%, 17.5% -130.1%, 4.4%-62.8%, 22.2%-68.7% under the subsoil layer, respectively. The fertility richness indices were increased in the subsoil layer, and nutrient contents of the subsoil layer were close to those of topsoil layer, indicating that 0-35 cm fertile soil layer had been constructed. 4) Soil organic matter con¬tents in the 0-35 cm layer were increased by 8.8%-23.2% and 13.2%-30.1% in the second and third years of fer-tile soil layer construction, respectively. Soil organic carbon storage was also gradually increased under fertile soil layer construction treatments. 5) The carbon conversion rate of organic matter was 9.3%-20.9% under T35+S treat¬ment, and 10.6%-24.6% under T35+M, T35+S+M, and T35+S+M+F treatments. The carbon sequestration rate was 815.7 - 3066.4 kg ⋅ hm² ⋅ a-1 in fertile soil layer construction treatments. The carbon sequestration rate of T35+S treatment increased with experimental periods, and soil carbon content under T35+M, T35+S+M and T35+ S+M+F treatments reached saturation point in the experimental second year. Construction of fertile soil layers could improve the fertility of topsoil and subsoil and maize yield. In term of economic benefits, combination application of maize straw, organic material and chemical fertilizer within 0-35 cm soil, cooperating with conservation tillage, is recommended for the Albic soil fertility improvement. [ABSTRACT FROM AUTHOR]

The conservation and utilization of black soil have achieved remarkable results under effective measures and active promotion taken by different departments in China. At present, the conservation and utilization of black soil have been upgraded to national strategy and incorporated into related planning and outline, major scientific advances have been achieved. The black soil conservation and utilization have also been listed into the important governmental schedules in Heilongjiang Province, Jilin Province, Liaoning Province, and Inner Mongolia Autonomous Region in Northeast China. The promotional mechanisms of black soil conservation and utilization have been established, approaches of black soil conservation and utilization have been proposed according to the local conditions, Lishu model and Longjiang model were established, soil fertility of six soil types in black soil has been enhanced, mass satisfaction has reached 100% according to the questionnaire survey, social and public participation awareness has been significantly improved. Additionally, black soil conservation and utilization could rely on related regulations and specifications under continuous improvement, and will rely on related national law in the future. Nevertheless, there are still a range of problems to be solved for further work in black soil conservation and utilization, such as whether the thick black soil layer can be maintained under current practices, whether soil with thin black soil layer can restore to soil with thick black soil layer by the technology innovation, how to simultaneously realize obstacle abatement and soil fertilization of albic soil with low input, and what are the threshold values of wind erosion and run off in black soil zone. In the future, black soil conservation and utilization should focused on strengthening top-level design, playing a full guiding role of Outline of the Northeast Black Soil Conservation (2017-2030) and Implementation Programme of National Black Soil Conservation Project (2021-2025), establishing black soil conservation zone in the north of black soil zone (N 45°) with area of more than 4x104 km² in order to reach the objective of black soil sustainable utilization, breaking through technical bottlenecks of constructing fertile cultivated layer for soil with thin black soil layer in order to realize improvement in black soil fertility and enhance the crop yield, building field observation stations with long slope in sloping arable areas focused on drainage technology with low energy and controlling groove erosion, setting up soil wind erosion monitor network in order to provide important reference for developing technology of controlling wind erosion. [ABSTRACT FROM AUTHOR]

Crop monoculture affects soil microbial community structure and diversity, but it is unclear which differences occur in microbial functions after the alteration of the bacterial community during crop monoculture. We investigated the diversity, functional groups and metabolic functions of bacteria under soybean rotation (RS), 2-year (SS) and 27-year (CS) soybean monoculture systems using high-throughput sequencing and functional prediction based on FAPROTAX and the Kyoto Encyclopedia of Genes and Genomes (KEGG). Original soil sample (OS) was taken as a reference point. Our results showed that CS had a lower abundance of the bacterial amoA gene than either RS or SS. Bacterial community differed more in OS than that in RS, SS and CS, and SS and CS had similar bacterial community and that they differed from RS. CS showed a lower relative abundance of predicted functional groups in terms of aerobic chemoheterotrophy, nitrate reduction and photoheterotrophy. KEGG annotation showed greater negative effects on the bacterial functional metabolism than positive effects in CS compared to RS. Redundancy analysis indicated that the predicted functional groups might be related to organic carbon and total nitrogen concentration, and that KEGG pathways were mainly affected by soil pH and available nitrogen. Abbreviations RS: soybean rotation; SS: two-year soybean monoculture; CS: long-term soybean monoculture; AOB: ammonia-oxidizing bacteria; qPCR: quantitative real-time PCR; OTUs: operational taxonomic units; SOC: soil organic carbon; TN: total nitrogen; AN: available nitrogen; TP: total phosphorus; AP: available phosphorus; AK: available potassium; PCoA: Principal coordinate analysis; KEGG: the Kyoto Encyclopedia of Genes and Genomes; RDA: redundancy analysis. [ABSTRACT FROM AUTHOR]