Optimum fertilization for high yield, high sucrose content and high profit of sugarcane (Saccharum officinarum) on different soil types Optimized model of agro-animal husbandry for black soil region of Songnen Plain and its implementation effect Study of the Optimized Model of the Forest Resources Exploitation The Optimized Model for Conversion of Farmlang to Forests in zhe Hill-Gully Subregion of Loess Plateau Mechanism analysis of optimized model of conversion from farmland to forestland in the hill-gully sub-region of Loess Plateau