Positional difference in potassium concentration as diagnostic index relating to plant K status and yield level in rice (Oryza sativa L.)

ABSTRACTPlant tissue testing is used as a guide for rice (Oryza sativa L.) fertilization and has been extensively used in the diagnosis of potassium (K) deficiency. However, little attention has been paid to the variation in the diagnostic index of K status in different parts of the rice plant. Here, we assessed the feasibility by testing K concentrations of whole plants, leaf blades and leaf sheaths to develop a suitable diagnostic index of plant K status and yield level in rice under different K application rates. The results showed that this research could satisfy the requirements of K status diagnosis, based on the quadratic-plus-plateau relationship between K application rates and grain yield. The K concentrations of the leaf blades and leaf sheaths on the main stem showed differences based on position. Leaf blade K concentrations significantly decreased from the top of the plant to the bottom in the effective tillering and jointing stages. Conversely, K concentrations in the lower leaf blades exceed...