Effects Of Grafting And BaseFertilizer On Soil Microbial Properties And Cucumber Growth In Protected Production Systems

Cucumber is one of the major greenhouse vegetable crops in China. However, continnous cropping is a common practice that often result in the obstacles of cucumbergrowth. Grafting and compost application are two effectiveagricultural practices used to improve soil quality and sustain soil productivity.Although these two practices often have positive effects on plant growth in continuous croppingsystems, which may be related to root-associated microbial properties, the related machinsm still needs to be uncovered.In this study, agreenhouse soilexperiment was conducted to investigate the effectsof grafting and compost application onsoil microbial properties and plant growth.The treatments include (i) self-root (SR)-chicken manure (CM),(ii) single-root-grafting (SRG)-CM,(iii) double-root-grafting (DRG)-CM,(iv) SR-CM-compost (CMC),(v) SRG-CMC, and (vi) DRG-CMC.Cucumberwere grown in soils during the autumn-winter (AW) and winter-spring (WS) seasons. For each cropping season, rhizosphere soil microbial properties, plant biomass and fruit yields were analyzed. Rhizosphere soil microbial properties were evaluated with a combination of microbial populations measured by quantitative PCR, microbial community composition analyzed by denaturing gradient gel electrophoresis,454pyrosequencing, and sole-carbon utilization capacity by microbial communities.The main results observed were shown as follows:(1) In general, DRG increased microbial abundance and total fruit yield,but decreased microbial diversity compared to SR and SRG SRG decreased microbial abundance and diversity, but increased total dry matter compared to SR. When compared to CM, CMC increased bacterial abundance, microbial diversity and cucumber fruit yield, but decreased fungal abundance and microbial diversity in the WS season. However, reverse trends were found in the AW season.(2) Although the grafting treatment did not statistically affect soil pHand electraical conductivity (EC), the base fertilizer treatment significantly influenced soil pH. Soil available nutrients were not statistically changed by both gratfing and base fertilizer treatments.Interestingly, however, both soil organic and total nitrogen were significantly increased by the CMC treatment compared to the CM treatment, and by the DRG treatment compated to the SR and SRG treatments, respectively.(3) Principal component (PC) analysis showed that plant biomass was significantly correlated with soil microbial properties (both P<0.01for PCI and PC2).The highest total fruit yield was generallyfound under the treatment DRG-CMC. These results suggest that DRG-CMC is a beneficial practice that could improve cucumber soil environment through increasing microbial metabolic, genetical and structural diversities, and finally increase cucumber yields. However, there are close but complex relationships between rhizosphere soil microbial properties and plant biomass.