The main environmental factors which can affect the yield of a rice and stemborer (Chilo suppressalis Walker) system, including nitrogenous fertilizer (x1), phosphate fertilizer (x2), density of transplanted seedling (x3), density of insect eggs (x4) and damage period (x5), were selected to carry out the experiments, based on an orthogonal and rotational design of quadratic regression at five different levels, in Baishiyi, Chongqing, in 1988. This has led to establishing two mathematical models: one for the...