Taking tomato variety‘Fenheping’and tillering onion variety‘Suihua’as experimental
material，this paper studied on the effects of tillering onion associated with reduced phosphorus treatment on tomato
growth，photosynthetic indexes and yield．The results indicated that the stem diameter in the treatment of tomato
inter-cropped with onion under reduced phosphorus condition（50% of conventional phosphorus fertilization）
30 days after planting was significantly thicker than that of the control（tomato monoculture and conventional
phosphorus fertilization）．Plant dry and fresh weights were also significantly higher than that of the control at the
seedling pulling stage. In addition，the photosynthetic rate，stomatal conductivity and transpiration rate of leaves
were obviousely higher than that of control during flowering period and fruiting period．Moreover，tomato single
plant yield was significantly higher than that of the control，indicating that tillering onion associated with tomato
cultivation could reduce the application rate of phosphate fertilizer．