Rice straw serves as additional carbon source for rhizosphere microorganisms and reduces root exudate consumption

Straw application is a common agricultural fertilisation practice, providing an additional carbon and nutrient source for soil microorganisms. We investigated the influence of rice straw application on root exudate consuming microorganisms in the rhizosphere of Zea mays based on (CO2)-C-13 pulse labelling and phospholipid fatty acid stable isotope probing (PLFA-SIP) in a paddy soil under rice-maize crop rotation. The application of straw decreased the labelling of microbial PLFAs in the rhizosphere of 30 and 40 day old maize plants by 70% compared to treatments without straw. This decrease could partially be explained by a lower rate of CO2 assimilation of the plant in the presence of rice straw. In addition, the uptake of root exudates by rhizosphere organisms was decreased due to the presence of the rice straw, which serves as an additional carbon source for these microorganisms.