Astragalus Research Articles

Effects of the Combined Application of Chinese Milk Vetch (Astragalus sinicus L.) and Red Mud to Remediate the Cadmium-Polluted Acidic Paddy Soil

In this study, we conducted field experiments to assess the effects of the combined application of Chinese milk vetch (Astragalus sinicus L., CMV) and red mud (RM) to remediate the cadmium-polluted acidic paddy soil. The results showed that the combined application increased the yield component index and improved the grain yields, compared with the control, RM1, RM2, and CMV treatments. However, the increased range of soil pH values in the CMV-RM1 and CMV-RM2 treatments was smaller than that of the RM1 and RM2 treatments at the different rice growth stages. The soil organic matter (SOM) contents of the RM-only treatments did not differ throughout the whole period, but were significantly different (p < 0.05) between CMV-RM2 and the control. Compared with the control, the combined application decreased the concentration of exchangeable Cd in the early rice soil. The combined application of CMV and RM substantially decreased the rice uptake of Cd. However, we found no significant difference (p < 0.05) between the CMV-RM1 and CMV-RM2 treatments. Therefore, compared with remediation with RM or CMV alone, we recommend the combined application of CMV and RM as an economical, highly effective, and replicable amendment for remediating acidic, Cd-polluted paddy soil. Considering the restorative effect and proper use of RM, we recommend CMV-RM1 treatment.

Soil Microbial Community Driven by Soil Moisture and Nitrogen in Milk Vetch (Astragalus sinicus L.)–Rapeseed (Brassica napus L.) Intercropping

The soil microbial community is not only driven by plant composition but is also disturbed by the soil environment. Intercropping affects the soil microenvironment through plant interaction, but the understanding of the relationship between soil microbial community and environment in intercropping is still weak. In this study, milk vetch intercropping with rapeseed was used to explore the interaction between soil microorganisms and environment. The results showed that the soil moisture content of intercropping was higher than that of monoculture during the reproductive period of rapeseed growth (flowering and podding stages). The contents of soil total nitrogen and alkali-hydrolyzable nitrogen in intercropping were higher than those in monoculture. The dominant soil microbial communities in intercropping were the same as in monoculture and included Chloroflexi, Proteobacteria, Actinobacteria, Acidobacteria, Firmicutes, Gemmatimonates and Bacteroidetes. However, intercropping increased the Shannon index and decreased the Simpson’s index of the soil microbial community. The changes in the soil microbial community were mainly related to soil temperature, moisture, pH, total nitrogen, alkali-hydrolyzable nitrogen and available potassium. Moreover, there was a negative correlation between soil moisture and microorganisms and a positive correlation between nitrogen and microorganisms. Thus, milk vetch–rapeseed intercropping could not only improve soil nitrogen content, but also change soil microbial community diversity. In dryland red soil, the effect of milk vetch–rapeseed intercropping on soil moisture and nitrogen was the key factor contributing to the changes in the soil microbial community. When planting rapeseed in the future, we could consider the application of intercropping with milk vetch, which can contribute to regulating the soil nitrogen pool and improving microbial diversity.

Long-term green manuring to substitute partial chemical fertilizer simultaneously improving crop productivity and soil quality in a double-rice cropping system

Rotation with Chinese milk vetch (MV) as winter green manure in double-rice cropping system is an efficient approach to substitute chemical fertilizer (CF). However, the optimal substitution rate of MV for CF and its long-term effects on crop productivity and soil quality remain unknown. We conducted a 13-year field experiment with different substitution rates of MV for CF (22.5 t ha−1 fresh MV incorporation with 100%, 80%, 60%, and 40% of the recommended nitrogen (N) and potassium (K) supply, represented by MV+F100, MV+F80, MV+F60 and MV+F40, respectively) to investigate its long-term effects on yield sustainability and soil quality in double rice cropping system. Compared with the sole application of CF, the MV+F100 and MV+F80 treatments significantly increased the early rice yields by 15.6% and 11.3% and the late rice yields by 9.3% and 6.3%, respectively. Utilization of MV to substitute 0–40% of the N and K in early rice season and 0–20% of the N and K in late rice season significantly increased the soil quality index (SQI). However, further increasing the substitution rate decreased the sustainability yield index (SYI) and SQI. The soil available phosphorus had a stronger effect on the early and late rice grain yield than the other soil physicochemical properties. Meanwhile, rice grain yields significantly increased with increasing SQI, and the apparent N, P and K balances positively affects SQI. The SYIs of early and late rice crops linearly increased with increasing SQIs, while the coefficient of variance in grain yield (CVy) decreased with increasing SQI. Consequently, long-term utilization of MV to substitute 0–40% of the N and K in early rice season and 0–20% of the N and K in late rice season can simultaneously improves yield sustainability and soil quality.

Changes in Phenolics and Antioxidant Capability of Two Chinese Milk Vetch Sprouts During Germination

Changes in Phenolics and Antioxidant Capability of Two Chinese Milk Vetch Sprouts During Germination

Effects of substitution of chemical fertilizer by Chinese milk vetch on distribution and composition of aggregates-associated organic carbon fractions in paddy soils

PurposeGreen manure plays a key role in reducing chemical fertilizer applications and increasing soil organic carbon (SOC) stock. The effects of chemical fertilizer substitution by Chinese milk vetch (MV) on the distribution and composition of organic carbon fractions in macroaggregates and microaggregates and SOC stability mechanism were investigated in paddy soils in southern China.MethodsA 10-year (2008–2018) field experiment was conducted, including no fertilizer (CK), 100% NPK fertilizer (F100), MV with different percentages of chemical fertilizer (MV + F100, MV + F80, MV + F60 and MV + F40). The soil was separated into distinct organic carbon fractions using aggregate density fractionation and SOC chemical structure was analyzed by fourier-transform infrared and nuclear magnetic resonance.ResultsChemical fertilizer substitution by MV increased SOC contents in the bulk soil by 9.1% (MV + F80), 5.8% (MV + F60), 17.9% (MV + F40) compared to F100. Organic carbon fraction mainly existed in mineral associated organic carbon (mSOC), accounting for 70.3–83.7% and 69.4–84.0% of the relative mass of macroaggregates and microaggregates, respectively. Compared to F100, aromatic C increased by 11.6% and 29.1% under MV + F60 within mSOC in macroaggregates and microaggregates. Within the mSOC in macroaggregates, compared to CK, MV + F80 and MV + F60 promoted the proportion of alkyl C by 9.6% and 6.7%, and decreased the content of O-alkyl C by 14.1% and 11.0%, respectively, which correspondingly increased alkyl C/O-alkyl C ratio.ConclusionsSubstitution of chemical fertilizer by MV (especially MV + F80 and MV + F60) improved the stability of SOC via increasing recalcitrant structure in mSOC, and was conducive to the sequestration of SOC in paddy soils.

Milk vetch returning reduces rice grain Cd concentration in paddy fields: Roles of iron plaque and soil reducing-bacteria

Milk vetch (MV, Astragalus sinicus L.) is used in agricultural production as a green manure; however, its impact on accumulation levels of heavy metals (e.g., Cd) in rice remains poorly understood. This study investigated the effects of MV on Cd accumulation in rice, iron plaque formation, soil properties, and the soil microbial community structure through field experiments. The results showed that MV reduced Cd concentration in the roots, stem, leaves, and grains by 33%, 60%, 71%, and 49%, respectively. Chemical fertilizer and MV treatment promoted iron plaque formation, and MV considerably increased the Fe/Mn ratio in the iron plaque. More importantly, MV inhibited Cd transportation from the root iron plaque to the root by 74%. The concentrations of CaCl2-extractable Cd, available phosphorus, and available potassium, as well as the cation exchange capacity and urease activity, were significantly reduced in the MV treatment. Furthermore, 16 S rDNA high-throughput sequencing results of the soil microbial community structure showed that compared with the control, MV increased the soil microbial richness, increased the relative abundance of anaerobic microorganisms, and significantly increased the relative abundance of Thermodesulfovibrio and Geobacter at the genus level. The increase in anaerobic microbial abundance was closely related to the decrease in CaCl2-extractable Cd concentration. The application of MV promoted the formation of iron plaque, inhibited the transport of Cd, increased the abundance of anaerobic microorganisms, decreased the CaCl2-extractable Cd concentration, and reduced the Cd concentration in rice grain.

Co-incorporation of Chinese milk vetch (Astragalus sinicus L.), rice straw, and biochar strengthens the mitigation of Cd uptake by rice (Oryza sativa L.)

Soil cadmium (Cd) contamination is becoming a widespread concern because of its threat to global ecosystem health and food security. Co-incorporation of Chinese milk vetch (MV) and rice straw (RS) is a common agricultural practice in Southern China; however, the effects of combining these two materials with biochar on Cd bioavailability remain unclear. This study investigated the effects of MV, RS, rape straw biochar (RB), iron-modified biochar (FB), and their combinations on Cd uptake by rice through incubation and field experiments. The results showed that compared with the control without material input (CK), MV + RS (MR), MV + RS + RB (MRRB), and MV + RS + FB (MRFB) considerably reduced the Cd concentration in brown rice by 61.20 %, 65.38 %, and 62.65 %, respectively. Furthermore, the treatments increased the formation of iron‑manganese plaque (IMP) at different growth stages; MRRB and MRFB exhibited the highest increase rates among the treatments. Quantitatively, the Fe plaque and Mn plaque were increased by 20.61 %–47.23 % and 80.18 %–172.74 %, respectively. Compared with CK, the MRRB and MRFB treatments reduced the soil available Cd by 35.09 %–54.45 % and 38.20 %–50.20 %, respectively, at all stages. This decrease was substantially lower than that observed in the MV, RS, and MR treatments. Similar trends were observed in the incubation experiment. Additionally, the Community Bureau of Reference Sequential Extraction Analysis indicated that the MRRB and MRFB treatments converted the bioavailable Cd fractions into a stable form. Partial least squares path model and redundancy analysis revealed that pH was the major factor influencing Cd bioavailability. This study emphasized that the dual impact factors from the enhancement of Cd passivation capability and IMP formation jointly result in the reduction of Cd uptake by rice. Consequently, the co-incorporation of MV, RS, and biochar is promising for remediating Cd-contaminated paddy soils in Southern China.

First report of milk vetch dwarf virus infecting Capsicum annuum L. in Korea

First report of milk vetch dwarf virus infecting Capsicum annuum L. in Korea

Combined application of chemical fertilizer with green manure increased the stabilization of organic carbon in the organo-mineral complexes of paddy soil.

The influence of the combined application of chemical fertilizer with green manure on the stabilization of organic carbon (C) was explored in the organo-mineral complexes of paddy soil. The organo-mineral complexes were isolated from paddy soil treated with no fertilizer, chemical fertilizer alone, and chemical fertilizer combined with increasing amounts of Chinese milk vetch (CMV). The stability (reflected by mineralizable carbon proportion), the content and chemical composition of organic C, the Fe/Al oxides and their associated organic C in the organo-mineral complexes were investigated. The application of chemical fertilizer in combination with CMV significantly improved the stability of organic C in the organo-mineral complexes. The combined application of chemical fertilizer with CMV slightly decreased the proportion of O-alkyl C (easily decomposed) yet somewhat increased the proportions of carbonyl C and aromatic C (difficultly decomposed) and aromaticity index in the organo-mineral complexes. The treatments of chemical fertilizer combined with CMV showed more Fe oxides and Fe/Al-associated organic C and higher proportion of Fe/Al-associated organic C in the total organic C of the organo-mineral complexes. The mineralizable carbon proportion displayed significantly negative correlations with carbonyl C and Fe/Al oxide-associated organic C in the organo-mineral complexes. The Fe/Al oxides were likely to be preferentially bound with the aromatic C and carbonyl C in the organo-mineral complexes. Overall, the combined application of chemical fertilizer with CMV facilitated the association of difficultly decomposed carbon and Fe/Al oxides, which significantly improved the stabilization of organic C in the organo-mineral complexes ofpaddy soil.

The Green Manure (Astragalus sinicus L.) Improved Rice Yield and Quality and Changed Soil Microbial Communities of Rice in the Karst Mountains Area

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.

First report of powdery mildew on Astragalus sinicus (Chinese milk vetch) caused by Erysiphe trifoliorum in China.

Astragalus sinicus L., (Chinese milk vetch) is a traditional leguminous green manure that plays a significant role in maintaining paddy soil fertility to enhance yield and the quality of rice in China. It is also found in gardens, roadsides, farms, fields, riverbanks, open wastelands, and is often used as livestock feed. From February 2019 to 2021, severe powdery mildew infections were observed on hundreds of A. sinicus grown in gardens and at roadsides of Fuzhou city, China. The disease incidence was up to 100% on leaves and stems of A. sinicus. White superficial fungal colonies (circular to irregular patches) were present on both sides of the leaves. Hyphae were flexuous to straight, branched, 4 to 8 µm in width, and septate. Hyphal appressoria were lobulate and solitary or in opposite pairs. Conidiophores were erect and straight, hyaline, and 60 to 120 × 8 to 10 µm (n=30). Foot cell was cylindrical, straight to slightly curved, 22 to 38 × 8 to 10 µm, followed by two to three shorter cells. Conidia were cylindrical-oval to doliiform, 30 to 48 × 13.5 to 24 μm with a length/width ratio of 1.6 to 2.4 (n = 30), formed singly, and without fibrosin bodies. Conidial germ tubes were produced subterminal position. No chasmothecia were found in the collected samples. The morphological characteristics of asexual structures were consistent with the descriptions of E. trifoliorum (Wallr.) U. Braun in Braun and Cook (2012). To verify the identification of the pathogen, the ITS and the part of large subunit (LSU) rDNA gene of the isolates were amplified using ITS1/ITS4 and LSU1/ LSU2 primers (Scholin et al. 1994 and White et al. 1990, respectively) and sequences were deposited in GenBank (ITS: MZ021332, MZ021333; LSU: MZ021334, MZ021335). In BLASTn searches, the ITS and LSU sequences were 99 to 100% identical with those of E. trifoliorum parasitic on Lathyrus magellanicus (LC010015), Medicago littoralis (LC270860), Melilotus officinalis (LC009924) and Trifolium spp., (MN216308, KY660821), as well as E. baeumleri (Bradshaw et al. 2021) on Vicia nigricans (LC010014). Pathogenicity test was performed by gently pressing a diseased leaf onto 10 young leaves of three healthy potted plants, while three non-inoculated plants were used as controls. All plants were maintained in a greenhouse at 20 to 25°C, without humidity control, and natural light. Symptoms developed 7 days after inoculation, whereas the control leaves remained symptomless. The morphology of the fungus on the inoculated leaves was identical to that observed on the originally diseased leaves. Powdery mildew on A. sinicus has been reported as E. pisi and E. polygoni from Korea and China (Shin, 2000; Tai 1979), respectively. Amano (1986) listed E. pisi and Microsphaera astragali (now E. astragali) on A. sinicus from China and Japan. To our knowledge, this is the first report of powdery mildew caused by E. trifoliorum on A. sinicus in China and in general. E. astragali is the most common and widespread powdery mildew species on Astragalus spp. (Braun and Cook 2012) and would be expected on A. sinicus, but this species is genetically clearly different from E. trifoliorum (Bradshaw et al. 2021). The E. trifoliorum complex (clade) is composed of several morphologically well-distinguishable species, besides E. trifoliorum also including E. baeumleri (on Vicia spp.), E. hyperici (on Hypericum spp.), and E. euonymi (on Euonymus spp.), but based on a combination of sequence plus host identity, the collection on A. sinicus can be assigned to E. trifoliorum (Bradshaw et al. 2021). The information in this study extended the host range of E. trifoliorum as well as future studies on A. sinicus in relation to powdery mildew outbreaks in China.

Genome-wide analysis of milk vetch dwarf virus and related alphasatellites from garlic and aphids in Shandong Province, China.

In 2019 and 2020, symptoms of dwarfing, yellowing, and reddening were observed in garlic in open fields in Shandong Province, China. Milk vetch dwarf virus (MDV) was detected in aphids and symptomatic garlic plants using polymerase chain reaction analysis. Furthermore, it was demonstrated using an aphid transmission test that garlic is a natural host of MDV. Rolling-circle amplification was combined with the use of specific primers to amplify the complete genomes of MDV and its related alphasatellites. This is the first report of complete genome sequences of MDV and related alphasatellites from garlic and aphid samples.

Rapid classification and identification of chemical components of Astragali radix by UPLC-Q-TOF-MS.

Pharmacological studies indicate that Astragalus (AR) has various bioactivities, including anticancer, antiaging, anti-inflammatory, antiviral, and antioxidant activities. Flavonoids, saponins, amino acids, and polysaccharides are the main active components in AR. However, its complex chemical compositions bring certain difficulties to the analysis of this traditional Chinese medicine (TCM). Therefore, there is an urgent need to establish a method for rapid classification and identification of the chemical constituents in AR. To establish a method for rapid classification and identification of the main components of flavonoids, saponins, and amino acids in AR. The samples were analysed with ultra-high-performance liquid chromatography time-of-flight quadrupole mass spectrometry (UPLC-Q-TOF-MS) and data post-processing techniques. Firstly, fragmentation information was obtained in the positive and negative ion modes. Then, to realize the rapid classification and identification of AR components, the characteristic fragmentations (CFs) and neutral losses (NLs) were compared with information described in the literature. A total of 45 chemical constituents were successfully screened out, including 22 flavonoids, 13 saponins, and 10 amino acids. The established method realised the efficient classification and identification of flavonoids, saponins, and amino acid compounds in AR, which provided a basis for further study on AR.

Replacing urea-N with Chinese milk vetch (Astragalus sinicus L.) mitigates CH4 and N2O emissions in rice paddy

Chinese milk vetch (Astragalus sinicus L) is a widely used leguminous green manure in paddy rice culture and has potential to replace or partly replace inorganic nitrogen (N) fertilizer. However, there is little quantitative information regarding replacing inorganic N with milk vetch on CH4 and N2O emissions. This study investigated the relationship between greenhouse gas production and carbon (C) and N release under 0%, 25%, 50%, 75% and 100% substitution of urea-N with milk vetch aboveground litter in a paddy soil. CH4 and N2O emission fluxes were measured using a static chamber method and milk vetch decomposition rates were tested by mesh bag method. After incorporation, C and N release from milk vetch followed a single exponential decay model, with 82.3–89.1% and 98.8–98.9% of the original C and N released during 125 days. CH4 flux was positively correlated with milk vetch substitution ratio, while it was negative correlated with N2O flux. Compared with 0% substitution, 25% substitution decreased global warming potential (GWP) and greenhouse gas intensity (GWP per unit of grain yield) by 12.1% and 10.3%, respectively, while 100% substitution increased GWP and greenhouse gas intensity by 38.4% and 65.2%, respectively. The results showed that soil pH, NH4+-N and redox state were significantly correlated with CH4 emission, while C and N remaining in the incorporated milk vetch residue and NH4+-N were key factors regulating N2O emission. It could be concluded that replacing 25% of urea-N with milk vetch was most effective in greenhouse gas mitigation while maintaining rice yield.

Responses of functional genes involved in nitrogen cycling to green manuring in different paddy soils in south China

AimsWe studied the effects of green manuring on the gene level of microorganisms associated with nitrogen (N) fixation, nitrification, and denitrification in different paddy soils.MethodsField experiments were conducted in Hunan, Jiangxi, Henan, and Fujian experimental sites in south China to investigate the responses of rice yield, soil properties, and functional genes to green manuring. The four treatments were no fertilizer application (NF), using milk vetch as green manure without chemical fertilizer (GM), winter fallow with chemical fertilizer (CF), and a combination of green manure and chemical fertilizer (GMCF).ResultsThe rice yield and N uptake significantly increased in GMCF. The nifH gene copies significantly increased in GMCF in the Jiangxi and Henan sites. Soil SOM, TN, NH4+-N, NO3−-N, AP, and AK were higher in GMCF than in the other treatments. For the nitrification process, the gene copies of ammonia-oxidizing archaea were higher than those of ammonia-oxidizing bacteria in all sites. The nirK and nosZ genes involved in denitrification were negatively correlated with soil properties. With the improvement of soil properties and rice N uptake, the denitrification process was inhibited in the GMCF treatment. The nirK gene was the most critical functional gene influencing rice yield among the tested genes. SOM was the most important factor among soil properties.ConclusionsThe application of green manure improved soil properties and changed the abundance of the functional genes involved in N cycling. Green manure combined with chemical fertilizer increased rice yields and N uptake and inhibited the denitrification process.

Seed Science and Technology. Volume 50 Issue 1 (2022)

This issue of Seed Science and Technology includes several papers in which the authors have conducted seed vigour research on species where little to no previous research has been reported. Seed vigour is an important attribute of seed quality and the ISTA Vigour Committee encourages research in seed vigour on a wide range of species. It is important within seed laboratories and the seed industry to have validated vigour tests that are simple, easy and practical, and are correlated to field performance or seed longevity. A range of seed vigour tests were explored in the papers of this issue of SST with a focus on the single count radicle emergence (RE) test and / or mean germination time (MGT) for Chinese milk vetch, Festuca sinensis, cucurbit rootstocks and dill, with practical application for each specific crop. A paper using MGT and RE to evaluate emerging technologies using plasma seed priming treatments for maize is also discussed.

Single count of radicle emergence and mean germination time estimate seed vigour of Chinese milk vetch (Astragalus sinicus)

This research explored the relationship between a single count of radicle emergence (RE) and mean germination time (MGT) with seed vigour for Chinese milk vetch (Astragalus sinicus) (CMV), a globally important legume used as a forage, green manure, and rotation crop. Fourteen seed lots of CMV were used to determine standard germination (SG), RE and MGT in the laboratory. Field experiments were conducted at two sites to measure the emergence performance including field emergence (FE), seedling dry weight (SDW) and simplified vigour index (SVI). The SG ranged from 89.0 to 95.5% and was not significantly correlated with field performance at either of two sites. However, both a single count of RE at 20 hours and MGT were highly predictive of FE, SDW and SVI at both sites (R2ranged from 0.612 to 0.897 for RE; 0.604 to 0.870 for MGT). The RE was positively related to field performance while MGT was negatively related. The seed lots with lower RE at 20 hours had lower FE and higher MGT. Overall, both RE at 20 hours and MGT are suitable indices for the vigour evaluation of CMV. However, a single count of RE is more accurate, quick and convenient.

Astragalus sinicus Incorporated as Green Manure for Weed Control in Corn.

Astragalus sinicus L. (milk vetch), one of the most widespread green manure species, is widely planted in the temperate zone. Eleusine indica L. (goosegrass), a serious annual weed in the world, has evolved resistance to some non-selective herbicides. The use of milk vetch as green manure for weed control in paddy fields was proposed. Aqueous extracts of milk vetch are known to exert a different level of phytotoxicity on weeds and crops. Phytotoxic substances contained in green manure were released into the soil by leaching at the initial stage and decomposition at the later stage after the return of green manure. Considering the need for searching new sustainable strategies for weed control, a question arises: “if milk vetch could be applied in goosegrass control, which stage is the most important to control goosegrass after milk vetch returned to the field, and at the same time, will the subsequent crop, corn (Zea mays L.), be affected by the side effects from milk vetch phytotoxicity?” In this study, the potential of milk vetch for goosegrass control was approached by repeated laboratory experiments, which include the aqueous extract experiment, decomposed experiment, and pot experiment. The effects of milk vetch returning to the field on maize were simulated by a pot experiment. The extract of milk vetch could significantly inhibit the germination of goosegrass at 2% concentration, and the inhibition enhanced with the increase of concentration. In the decomposed liquid experiment, decay time within 15 days, with the increase of decay days or concentration, goosegrass inhibition effect of decomposed liquid was enhanced. When decay time was more than 15 days, the inhibition ability of the decomposed liquid to goosegrass decreased. According to the RI accumulated value, aqueous extract and decomposed liquid have a “hormesis effect” on the germination and growth of goosegrass. Pot experiment proved that the addition of 1–10% (w/w) of milk vetch significantly reduced the germination and growth of goosegrass. On the contrary, the comprehensive analysis showed that the participation of milk vetch was conducive to the growth of corn. Our results constitute evidence that the incorporation of milk vetch into the soil could be a feasible practice to reduce weed infarctions in the corn-based cropping system.

Effects of bio-mulching on wheat soil microbial community and carbon utilization efficiency in southwest China

Bio-mulching is a common agricultural practice in southwest China to improve crop productivity and soil fertility. In this study, a field experiment to investigate the effects of Chinese milk vetch (Astragalus sinicus L.) mulching and soybean straw retention (at the rate of 2250 and 4500 kg ha−1) on wheat soil microbial community and carbon utilization efficiency was conducted in southwest China. Results showed that the alpha diversity indices (Chao and Shannon) of bacteria and fungi in milk vetch mulching treatment were significantly increased in the wheat non-rhizosphere soils compared with control soil (without mulching). Within the bacterial community, the relative abundance of Actinobacteria and Chloroflexi was significantly increased by milk vetch mulching over the control, while the relative abundance of Acidobacteria, Firmicutes, Verrucomicrobia, and Gemmatimonadetes were significantly decreased in both wheat rhizosphere and non-rhizosphere soil. Within the fungal community, the relative abundance of Basidiomycota was significantly increased in milk vetch mulching treatment than that of control. By contrast, the differences in microbial diversity and community structure between the soybean straw retention and control were not distinctive. The correlation analysis revealed that wheat soil moisture, soil nitrate content, microbial biomass carbon, dissolved organic carbon and nitrogen content were closely related to the soil microbial community structure under different mulching practices. Results of the Biology ECO-plate revealed that all bio-mulching practices have enhanced the carbon source utilization rate. In addition, the relative abundance of Actinobacteria and Basidiomycota has a positive correlation with the metabolism rate of carbon substrates, such as glycyl-L-glutamic acid, I-erythritol, D-xylose, and α-cyclodextrin. Overall, our results suggested that bio-mulching, especially milk vetch mulching, has changed greatly the soil microbial community structure and function in the wheat rhizosphere.

Border-rows Effect of Rape (Brassica napus L.) Intercropping with Milk Vetch (Astragalus sinicus L.)

Border-rows effect is an important research content of intercropping system. Milk vetch-rape intercropping is one of the typical intercropping patterns in southern China. However, research on the border-rows effect is very little, which has affected the application and popularization of the milk vetch-rape intercropping system. In this study, two field experiments were conducted from 2018 to 2020. The effects of monoculture, intercropping and different border-rows on agronomic traits and yield of rape were studied. The results showed that milk vetch had a significant effect on the first border-row of rape. The first border-row of rape diameter of root and secondary effective branch number is significantly higher than second and third border-row, and the rape yield per plant in the first border-row of intercropping milk vetch was 135%, 328%, 257% and 147% higher than that in the second, third, fourth and fifth border-rows respectively. The intercropping with milk vetch enhanced the number of pods per plant in first border-row by increasing the agronomic traits of rape, such as plant height, stem diameter, primary effective branch number and secondary effective branch number. In conclusion, intercropping milk vetch significantly improved the agronomic traits of the first and second border-rows rape, increased the yield of rape. So it is recommended that milk vetch intercropping with two rows rape, which has important guiding significance for the application and promotion of milk vetch-rape intercropping in the future.