Objectives The coexistence of potato onions increased tomato yield. This article studied the effect of coexistence on the rhizosphere soil functional microbial structures and the resulted nutrient absorption and distribution characteristics, of tomato, to reveal the microbiological mechanisms caused by which interspecific interactions.

Methods A field experiment was carried out under shedding condition to examine the yield and nutrient uptake effect of co-cultivation on tomato.Three treatments were set up, including tomato monoculture, and co-cultivation of tomato with potato onion cultivar Wuchang, or Nong’an. The nutrient content of various parts of tomato plants were measured at 90 days after tomato transplanting (at tomato fruiting period). A pot experiment was carried out, with the same three treatments like field experiment for measuring root vitality, leaf chlorophyll content, and dry matter accumulation of tomato plants, and calculating the competition coefficient (Ato) and relative yield (RYT) of tomato potato and onions under Co-cultivation; Aga plating method was used to cultivate the microorganisms of the rhizosphere soil from the field experiment, PCR sequencing method was used to identify the species and relative abundances of functional bacteria and fungi, and to invstigate the diversity of microbial structures.

Results ① The Co-cultivation promoted the absorption of N, P, K, Mn, Mo, Si, and B by tomato, and increased the allocation proportion of the nutrients in tomato roots, flowers, and fruits, while decreased the allocation in tomato leaves, resulting in an increase in nutrient utilization efficiency. ②The Co-cultivation significantly increased the shoot and root dry weight, and the root shoot ratio of tomatoes, the RYT values of the two Co-cultivation treatments were all greater than 1. The relative Ato of tomatoes under Co-cultivation was far higher than 0, so tomato showed interspecific dominance and achieved significantly higher biomass accumulation under Co-cultivation. ③The leaf chlorophyll content of Co-cultivationd tomato was signifcantly higher than that of monocultured tomato at 23 days of transplanting, but the difference was not significant at the 90 days, while.the root activity of Co-cultivationd tomatos was significantly higher than that of monocultured plants throughout the entire intercropping period. ④The relative abundance of unknown functional bacteria such as Pseudomonas, Bacillus, Rhizobium, and Microbacterium in the rhizosphere soil of Co-cultivationd tomatos significantly increased, and new bacterial genera such as Sphingobium and Ochrobactrum were identified, while Arthrobacter and Acinetobacter disappeared. The changes in the structures of functional microbial communities are conducive to increas the availability of nutrients in rhizosphere soil of Co-cultivationd tomatoes.

Conclusions The co-cultivation of tomatoes and potato onions could improve the functional structures of microoganisms in rhizosphere soil of tomato, which are conducive to the nutrient absorption of Co-cultivationd plants. Tomato has competition advantages in the co-cultur system, so Co-cultivation exaggerate the nutrient absorption, allocation to reproductive organs, and the growth and yield formation of tamatos.