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The use of green manure plants for soil restoration is a viable agricultural practice that can mitigate soil degradation and biodiversity loss caused by the long-term application of inorganic fertilizers. However, the effects of green manure on soil microbial communities, rice yield, and quality in the karst mountains are largely unknown. The effects of no chemical fertilizer, chemical fertilizer, chemical fertilizer + different Astragalus sinicus L. (Chinese milk vetch, CMV) treatments on the microbial community, soil enzyme activities, soil nutrient content, and crop yield were investigated through field experiments. A moderate application of chemical fertilizer with green manure can increase chlorophyll content, increase effective rice spikes, positive impact on rice yield, and increase crude protein, etc. Additional application of the moderate amount of CMV can increase alkali-hydrolyzable nitrogen and available phosphorus (a significant increase of 54.87–72.65%), improve microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) (CFMV2 significantly increased by 22.16%), improve soil urease and phosphatase activities, and the urease activity increased by 43.43–69.24% with CMV application compared to CK. Moreover, all bacterial communities were dominated by three major phyla (Proteobacteria, Chloroflexi, and Acidobacteria), where the application of chemical fertilizer with CMV increased the ratio of abundance of Proteobacteria and Acidobacteria in rice soils, and the effect of chemical fertilizer application on the dominant bacteria was regulated to some extent by additional green manure application, which may have a beneficial effect on rice yield. Therefore, we conclude that the rational use of chemical fertilizers with CMV (22,500 kg ha−1) in karst landscapes is one of the effective measures to achieve efficient and sustainable use of rice fields.

Phytostabilization has become an efficient in situ remediation technology. In order to investigate the tolerance and environmental effects of Chinese milk vetch ( Astragalus sinicus L.) planted in Cu-contaminated soil, pot experiments were conducted. In this experiment, Chinese milk vetch had been planted in soil with gradual Cu concentrations (0, 200, and 400 mg kg −1 ) for 5 months. The indicators of plants and soil were determined after planting, such as physiological indexes, biomass and bioaccumulation of Chinese milk vetch, total nitrogen and available Cu in soil, and composition of soil microbial community. Chinese milk vetch could maintain a stable physiological state and strong nitrogen fixation ability in Cu-contaminated soil, and activate Cu in soil to absorb it in roots. Meanwhile, the soil microbial community compositions were affected by the planting of Chinese milk vetch. Chinese milk vetch could be planted as a candidate reclamation plant in Cu-contaminated soil due to its Cu tolerance and play a role in phytostabilization of heavy metals while keeping its agricultural value as green manure.

BackgroundExcessive application of chemical fertilizer has resulted in lower nitrogen uptake and utilization efficiency of crops, decreasing soil fertility, increasing greenhouse gas emissions, and worse environmental pollution. Organic material retention is regard as the key to solve these problems. The objective of this study is to conduct an assessment of carbon budget under Astragalus sinicus L. and rice straw retention combined with reduced mineral fertilizer based on the 2-year field experiment in a paddy field in the south of China. The experiment was randomized complete block design including four treatments with triplicates: control CK (winter follow, 120 kg ha−1 N fertilizer for each rice season) and three treatments with Astragalus sinicus L. and rice straw retention named RA, RB, and RC (reduced N fertilizer by 15%, 27.5%, and 40% in each rice season).ResultsTreatments RA, RB, and RC increased greenhouse gas emissions by 9.30–101.25%, among which CH4 accounted for more than 60%; Carbon input of crops from treatments RA, RB, and RC increased by 2.25–12.10% compared with control CK over the 2 years. Though treatments RA, RB, and RC enhanced CO2 emissions, treatment RB decreased carbon footprint and became carbon sink.ConclusionsThe results of this study reveal that treatment RB (Astragalus sinicus L. and rice straw retention with reduced N fertilizer by 27.5%) is better in reducing chemical fertilizer amount, increasing crop yield and carbon input, which is more conductive to sustainable development of agriculture.

Inflammation is a part of the complex biological responses of a tissue to injury that protect the organ by removing injurious stimuli and initiating the healing process, and is considered as a mechanism of innate immunity. To identify biologically active compounds against pathogenic inflammatory and immune responses, we fractionated water, aqueous methanol and n -hexane layers from nine kinds of leguminosae and examined anti-inflammatory activity of the fractions in human keratinocytes and mouse skin. Among the fractions, rf3 and rf4, isolated from the aqueous methanol layer of Astragalus sinicus L., exhibited the strongest reactive oxygen species (ROS)-scavenging and anti-inflammatory activities as measured by inhibition of the intracellular ROS production, nuclear factor-kappaB (NF-κB), janus kinase (JAK)/signal transducer and activator of transcription (STAT), and phosphatidylinositol 3-kinase/Akt signaling in cytokine-stimulated human keratinocytes, as well as by effects on T-cell differentiation in mouse CD4 + T cells. In addition, topical application of rf3 and rf4 suppressed the progression of psoriasis-like dermatitis and expression of pro-inflammatory mediators in interleukin (IL)-23-injected mouse ears. Our results suggest that Astragalus sinicus L. may ameliorate chronic inflammatory skin diseases due to its antioxidant and anti-inflammatory activities via regulation of the intracellular ROS production, NF-κB, JAK/STAT and PI3/Akt signaling cascades as well as immune responses, and these results are the first report that Astragalus sinicus L. exhibits pharmacological activity. Immunology: A home-grown inflammation remedy Extracts from an Asian legume exhibit anti-inflammatory properties that may prove useful in treating certain immune disorders. Inflammatory pathways are a valuable first line of defense for the immune system, but can cause severe tissue damage and medical problems without effective anti-inflammatory controls. Researchers led by Tae-Yoon Kim of the Catholic University of Korea prepared extracts from nine different Asian plants in an effort to identify new compounds with anti-inflammatory properties. Their analysis revealed that two fractions derived from the Chinese milkvetch, Astragalus sinicus , can suppress the production of inflammatory cell signals and inhibit the proliferation of immune cells associated with allergy and autoimmune disease. Kim and colleagues subsequently demonstrated that both extracts can also reduce tissue damage in a mouse model of psoriasis, providing further evidence that these fractions contain therapeutically useful compounds.

A greenhouse experiment was conducted to study the effect of mycorrhizal colonization by Gigaspora margarita, Glomus intraradices, and Acaulospora laevis on nutrient uptake of K, Ca, Mg, Cu, Zn, Fe, and Mn by Astragalus sinicus L. in soils spiked with lanthanum at five rates (0, 1, 5, 10, and 20 mg kg⁻¹). Lanthanum application significantly decreased the concentrations of K, Ca, Mg, Cu, Zn, and Fe in shoots and the concentrations of Cu and Zn in roots. Mycorrhizal treatments markedly improved uptake of nutrients, and these results are important since nutrient deficiency often occurs in contaminated sites.

Thirteen nodule-specific or nodule-enhanced genes have been revealed by suppressive subtractive hybridization (SSH) with two mRNA populations of infected and uninfected control roots of Astragalus sinicus. Eleven of them encode small polypeptides showing homology to cysteine cluster proteins (CCPs) that contain a putative signal peptide and conserved cysteine residues. Among these CCP-like genes, AsG257 codes for a homologue of the defensin 2 family and AsD255 contains a scorpion toxin-like domain at the C-terminus. Sequence analysis of a genomic AsD255 fragment which was isolated revealed that one intron separates the first exon encoding the signal peptide from the second exon encoding the cysteine cluster domain of this nodulin. Another two genes, AsE246 and AsIB259, encode two different products similar to lipid transfer proteins (LTPs). Virtual northern blot and reverse transcription–polymerase chain reaction (RT–PCR) analysis indicated that the other genes except AsIB259 and AsC2411 were expressed exclusively in inoculated roots and that their expression was 2–4 d later than that of the leghaemoglobin (Lb) gene during nodule development. Transcription of AsIB259 was also detected in uninfected control roots but with a significant decline in expression and a temporal expression similar to Lb. AsC2411 had a basal expression in control roots identified by RT–PCR. Sequence alignment showed that the putative proteins AsE246 and AsIB259 show lower homology with LTPs from legumes than with those from other plants.

Rice straw (RS) was incorporated into paddy soil together with leguminous green manure (e.g., Chinese milk vetch, Astragalus sinicus L., MV) in a mesocosm-scale experiment and the enzyme activity and composition of main microbial groups were measured. Mixing MV and RS caused a synergistic release of residual C and N, leading to a low C/N ratio at the middle and late decomposition stages of the mixture and shortening the time to complete decomposition. Furthermore, the highest abundances of Gram-negative (G−) bacteria and fungi and the highest activities of α- and β-glucosidase, β-cellobiosidase, β-xylosidase, N-acetyl-glucosaminidase, and acid phosphomonoesterase were observed in the residue mixture, especially at the middle and late stages of the experiment. The residue decomposition rate was positively correlated with residual N and mineral N concentrations. Most hydrolases and both oxidase (phenol oxidase and peroxidase) activities, and G− bacterial (especially 18:1 ω5c, Photobacterium) abundance explained the decomposition of mixing residues. In conclusion, co-incorporation of MV and RS could stimulate their decomposition by retaining a relatively low C/N ratio, enhancing G− bacterial abundance and hydrolase activities. Introducing leguminous green manures in paddy fields may be an effective way to accelerate the decomposition of rice straw.

Arbuscular mycorrhizas contribute significantly to inorganic phosphate (Pi) uptake in plants. Gene networks involved in the regulation and function of the Pht1 family transporters in legume species during AM symbiosis are not fully understood. In order to characterize the six distinct members of Pht1 transporters in mycorrhizal Astragalus sinicus, we combined cellular localization, heterologous functional expression in yeast with expression/subcellular localization studies and reverse genetics approaches in planta. Pht1;1 and Pht1;4 silenced lines were generated to uncover the role of the newly discovered dependence of the AM symbiosis on another phosphate transporter AsPT1 besides AsPT4. These Pht1 transporters are triggered in Pi-starved mycorrhizal roots. AsPT1 and AsPT4 were localized in arbuscule-containing cells of the cortex. The analysis of promoter sequences revealed conserved motifs in both AsPT1 and AsPT4. AsPT1 overexpression showed higher mycorrhization levels than controls for parameters analysed, including abundance of arbuscules. By contrast, knockdown of AsPT1 by RNA interference led to degenerating or dead arbuscule phenotypes identical to that of AsPT4 silencing lines. AsPT4 but not AsPT1 is required for symbiotic Pi uptake. These results suggest that both, AsPT1 and AsPT4, are required for the AM symbiosis, most importantly, AsPT1 may serve as a novel symbiotic transporter for AM development.

Aims In comparison to the accumulated knowledge related to the legume-cereal intercrops, very little is known on both basic and applied aspects of the legume-brassica intercrops. In fact, the potential of legume-brassica intercrops was enormous to improve crop yields, biomass, nitrogen uptake, the economic reliability via land equivalent ratio, and so on. Therefore, in the present study, the Chinese milk vetch ( Astragalus sinicus L.)-rape ( Brassica napus L.) intercropping system was investigated. The specific objective of this study was to investigate how Chinese milk vetch affects the soil microbial community in rhizosphere of rape. Methods A series of bucket experiments based on Chinese milk vetch-rape intercrops, included root separation and straw mulching, were employed to explore the soil properties and soil microbes in rhizosphere of rape. Results Intercropping substantially decreased the organic carbon content and the total nitrogen content and changed the C/N ratios. Intercropping also decreased the soil microbial biomass in rape rhizosphere (including the total PLFAs, bacteria, actinomycete, AM-fungi, and so on). In addition, intercropping and straw mulching also changed the structure of soil microbial community in rape rhizosphere, which was significantly correlated with 16:1w9c and 18:3w6c (6, 9, 12). At the same time, under the influence of intercropping Chinese milk vetch, soil microbial functional activity in rape rhizosphere was significantly reduced. Soil microbial community functional composition in rape rhizosphere was also changed greatly by intercropping, which was significantly correlated with d -glucosaminic acid and g-1-phosphate under no straw mulching, and glycogen, d -xylose and 2-hydroxy benzoic acid under straw mulching. Conclusions Intercropping Chinese milk vetch decreased soil microbial biomass and functional activity and changed greatly the soil microbial community structural and functional composition in rape rhizosphere. Our findings revealed that root interaction between Chinese milk vetch and rape was a crucial factor to manage the crop intercropping, which might, in turn, determine the soil microbe on rhizosphere.

Background and aims Although variations in microbial communities and residue components have been detected during the decomposition of monospecific and mixed plant residue in soils, little is known about the response of specific taxa to different residue types and their interactions with other microorganisms. Methods We compared the decomposition dynamics, recruited microbial community, and lignocellulolytic genes during the decomposition of leguminous milk vetch (MV), non-leguminous rice straw (S), and their mixed residue (SMV) to reveal the mechanisms of microbial-driven residue decomposition in soil. Results The residue remaining weight and main lignocellulose component contents exhibited varied periodic dynamics during decomposition. The SMV treatment maintained a relatively high decomposition rate, particularly at the early stages. Actinobacteria , Alphaproteobacteria , Gammaproteobacteria, and Sordariomycetes were enriched in S treatment. Eurotiomycetes and Bacilli were enriched in MV treatment, while Mucoromycetes was enriched in SMV treatment. Co-decomposition of residues increased the alpha diversity of the microbial community and enriched the Mucorales by increasing its niche breadth. Redundancy analysis (RDA) revealed that Mucorales was a key functional taxon with high lignocellulolytic potential. Conclusion Our study indicated that co-decomposition could widen the niche breadth of specific microbial species facing competitive condition during decomposition. Also, they could recruit more functional groups, maintain decomposition efficiency, and promote residue decomposition.