AUTHOR=Hou Wenfeng , Tränkner Merle , Lu Jianwei , Yan Jinyao , Huang Siyuan , Ren Tao , Cong Rihuan , Li Xiaokun 

TITLE=Diagnosis of Nitrogen Nutrition in Rice Leaves Influenced by Potassium Levels

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 11 - 2020

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.00165

DOI=10.3389/fpls.2020.00165

ISSN=1664-462X

ABSTRACT=Evaluation of the nitrogen (N) status by leaf color is a kind of classic nutritional diagnostic method. However, the color of the leaves is influenced not only by N, but also by other nutrients such as potassium (K). Two-year field trials with a factorial combination of N and K were conducted to investigate the effects of different N and K rates on soil plant analysis development (SPAD) readings and leaf N, K, magnesium (Mg), and chlorophyll contents. Visual inspections of leaf greenness revealed darker green leaves with the increasing N rates, while paler green leaves with the increasing K rates. Data showed that the SPAD readings, chlorophyll, N and Mg contents, and the chloroplast area increased significantly with the increase of N rates, while declined sharply with the increase of K rates due to the antagonistic relationships between K+ and NH4+ as well as Mg2+. It was also probably that the increase of K promoted the growth of the leaves and diluted the N and Mg content of the leaves. The paler leaf appearances resulted from the application of K may overestimate the actual demand for N in the diagnosis of rice N status, which was not a reliable estimate of N demand and grain yield. The strong antagonistic relationships among K+, NH4+ and Mg2+ should be considered in rice production and fertilization.