Root exudates increase phosphorus availability in the tomato/potato onion intercropping system

Abstract

Crop diversification usually increase nutrient use efficiency and productivity of crops, but we still lack deeper understandings of the underlying mechanisms. Here we aimed to study the role of root exudates and soil microbial communities in mobilization of soil P during an intercropping system. Different barrier treatments were used to separate tomato and potato onion, and different P forms, that makes most of the plant sparingly available P in the soil (i.e., Al-P, Fe-P, Ca-P, Organic P), were applied in a pot experiment. In addition, we studied the effects of monoculture and/or intercropped tomato root exudates in vitro on soil available P and soil microbial community composition using quantitative PCR and high throughput sequencing. Compared with solid barrier, the 30 μm barrier increased belowground tomato biomass in presence of Ca-P, O-P and no P, soil available P in presence of Al-P, Fe-P and Ca-P, increased abundance of Bacillus spp. in presence of Fe-P, Ca-P and O- P, Pseudomonas spp. in presence of all P forms, and Trichoderma spp. in presence of Al-P, Ca-P and O-P. Compared with control, in vitro root exudates of intercropped tomato activated all P forms examined in this study, and increased soil available P was positively correlated with abundances of Bacillus, Pseudomonas and Trichoderma spp., and relative abundances of Massilia and Planomicrobium. The bacterial community structure and diversity was altered in intercropped tomato root exudates treatment as compared to rest of the treatments. These findings suggest the key role of root exudates in increased bioavailability of soil P in the intercropping of tomato and potato onion.