Abstract: Selecting Zhengdan958 as the test materials, an experiment with a single factor and randomized blocks was designed to study the effects of planting density on yield and related traits of summer maize under the field planting conditions. The results indicate that the yield per unit area of summer maize in Tianjin increased firstly with planting density increase, but then decreased when the planting density reached a certain level. In a word, the yield showed quadratic curve changes with the planting density increase. Planting density influenced obviously on 1 000-kernel weight and grain number per ear and showed decrease by linear model. Planting density also influenced obviously on spike numbers, empty stalk rate, ear height and row number per ear and showed increase by linear model. Planting density had no notable effects on height of plant.

Key words: summer maize, planting density, yield, yield property