The model of first class market was y = - 0 . 2612x3 + 5 . 518x2 - 38 . 473x + 129 . 05 ( r2 = 0 . 812 ) . the model of first class market disclosed the phenomenon of three obvious influence phases . at the range of 0 - 5 km around the first class market , the influence of market on the vegetable plot quality changed faster , and the range belonged to a zone of high investment - output in vegetable planting 一级市场模型为y = - 0 . 2612x ~ 3 + 5 . 518x ~ 2 - 38 . 473x + 129 . 05 ( r ~ 2 = 0 . 812 ) ，该模型揭示了一级集贸市场对菜地质量的影响随距离变化表现出明显的三段性，即一级市场周围0 5公里范围内为影响变化较快，属于蔬菜种植高投入高产出区； 5 9公里范围内影响变化平稳，属于蔬菜种植投入产出过渡区； 9 14公里范围内影响变化再次变快，属于蔬菜种植低投入产出区。
