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Introduction: Intercropping has a potential to reduce the CO2 emission from farmlands. Limited information is available on the underlying reasons. Methods: This study investigated the effect of milk vetch (Astragalus sinicus L.) (MV), rapeseed (Brassica napus L.) monoculture (RS) and intercropping (Intercrop) on soil CO2 emissions, moisture and temperature in a bucket experiment during 210 days from October 2015 to May 2016 on Chongqing, China. Results: The results showed that soil CO2 efflux of MV, RS and Intercrop was 1.44, 1.55 and 2.08 mmol·m-2·s-1 during seedling and stem elongation stages and 3.08, 1.59 and 1.95 mmol·m-2·s-1 during flowering and podding stages. At seeding and stem elongation stages Intercrop had 1.4 times higher soil CO2 efflux than the mean of MV and RS. In contrast, MVhad 1.6 times higher soil CO2 efflux than Intercrop thereafter, which shows it was inhibited if milk vetch presents as Intercrop only. Decreased sensitivity of soil respiration to temperature in 1.4 times and lower soil moisture by Intercrop were found compared to MV. Intercrop decreased soil moisture, especially at the seedling and stem elongation stages, compared to the monoculture. The fluctuation on soil respiration in RS and Intercrop was slight with changes in soil moisture. Conclusion: Thus, milk vetch-rapeseed system has a potential to decrease CO2 emission from farmland, however soil moisture should be regulated properly. [ABSTRACT FROM AUTHOR]

IntroductionIntercropping has a potential to reduce the CO2 emission from farmlands. Limited information is available on the underlying reasons.MethodsThis study investigated the effect of milk vetch (Astragalus sinicus L.) (MV), rapeseed (Brassica napus L.) monoculture (RS) and intercropping (Intercrop) on soil CO2 emissions, moisture and temperature in a bucket experiment during 210 days from October 2015 to May 2016 on Chongqing, China.ResultsThe results showed that soil CO2 efflux of MV, RS and Intercrop was 1.44, 1.55 and 2.08 μmol·m-2·s-1 during seedling and stem elongation stages and 3.08, 1.59 and 1.95 μmol·m-2·s-1 during flowering and podding stages. At seeding and stem elongation stages Intercrop had 1.4 times higher soil CO2 efflux than the mean of MV and RS. In contrast, MVhad 1.6 times higher soil CO2 efflux than Intercrop thereafter, which shows it was inhibited if milk vetch presents as Intercrop only. Decreased sensitivity of soil respiration to temperature in 1.4 times and lower soil moisture by Intercrop were found compared to MV. Intercrop decreased soil moisture, especially at the seedling and stem elongation stages, compared to the monoculture. The fluctuation on soil respiration in RS and Intercrop was slight with changes in soil moisture.ConclusionThus, milk vetch-rapeseed system has a potential to decrease CO2 emission from farmland, however soil moisture should be regulated properly.

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. [ABSTRACT FROM AUTHOR]