Fertilizing model for Djulis (Chenopodium formosanum Koidz.) using mixture design approaches

Djulis (Chenopodium formosanum Koidz.), a cereal plant native to Taiwan, was used for wine making, insect repellant, and health promotion. Therefore, using appropriate experimental design and modeling approach is of importance to predict the effect of the interaction among nitrogen (N), phosphorus (P), and potassium (K) on djulis yields. In this study, a mixture design approach was applied to investigate the effects of interactions among nitrogen, phosphorus and potassium on the grain yields of djulis plants. Based on a three-variable including N, P, and K with each maximum of them was of 200 g (6 m2)-1, a mixture design approach was employed by 42 experiments in 14 study plots to obtain an optimal combination of N : P : K= 100 : 200 : 100 (g / 6 m2)-1) to predict an optimal dry djulis yield of 52.80 g / plant in this study. This study revealed that the linear mixture of N, P, and K and the interaction of P and K had marked effects on the yields of djulis. Moreover, the results were fitted to a quadratic polynomial equation using a multiple regression analysis. Our data showed this mixture design is a reliable approach to develop a model that can be used to predict the djulis yields