Abstract:To explore whether crop plant can recognize its kin neighbors, and how it responds in different environmental conditions, field studies were conducted, with the interaction effects of three factors, including neighbor identity (kin plant, non-kin plant and stranger plant), plant density and soil nutrient level, on the aboveground biomass allocation of Setaria italica. Results showed that the net reproductive biomass allocation and seed biomass allocation of S. italica planted with neighboring kins increased and the vegetative biomass allocation decreased significantly than those planted with neighboring non-kins. Under high plant density, the ear length, net reproductive biomass allocation and seed biomass allocation of kin group of S. italica were significantly higher than those of non-kin group (P<0.05), while the vegetative biomass allocation was lower. As soil nutrient level increased, the proportion of biomass allocation to seed of S. italica planted with neighboring kins significantly increased, while that of vegetative biomass allocation significantly decreased (P<0.05). It suggested that S. italica can recognize its kin neighbors, and this ability was regulated by plant density and soil nutrient level. Under high plant density and soil nutrient level, the ability of S. italica to recognize its kin neighbors tended to be stronger.