抄録
Fluid analysis is an effective method to diagnose the nutrition of field crops to determine the fertilizer application for stable yield, high quality and low load on the environment. We conducted field experiments using potato to determine the fluid properties of leaf petiole and the optimum values of nitrogen and phosphorus diagnosis for potato. The fluid was extracted using a garlic squeezer after cutting the leaf petiole. The contents of nitrate nitrogen (NO_3-N) and inorganic phosphorus (P) in the fluid were measured. 1. The weight ratios of the extracted fluid to the leaf petiole were 0.22-0.37. NO_3-N concentration in the petiole fluid was nearly the same as that in the leaf petiole, but inorganic P concentration in the petiole fluid was lower than that in the leaf petiole. 2. NO_3-N and inorganic P concentrations in the fluid well reflected the plant nutritional status of nitrogen and phosphorus, because they were highly correlated with the total N and P contents in the plant top, respectively. NO_3-N concentration in the fluid reflected the amount of applied N at the bud sprouting stage and flowering stage, and inorganic P concentration in the fluid reflected the amount of applied P only at the bud sprouting stage. 3. For sufficient yield and quality, the optimum value of the NO_3-N concentration in the fluid of leaf petiole at the bud sprouting stage was 1.3-1.5 g L^<-1> and that of inorganic P was about 100 mg L^<-1>.
