Abstract: By using the foliar nutrient diagnosis methods such as critical concentration value approach (CCVA), graph diagnosis and recommendation integrated system (DRIS), and index DRIS, this paper studied the relationships between the seed yield and its azadirachtin content and the foliar nutrient contents of seeding Azadirachta indica plantations in Yuanmou dry-hot valley. There existed significant linear correlations between the nutrient contents of foliages collected in June and the seed yield. In high-yielding plantations, the optimal contents of foliar total N, total P, and total K were 15.09-22.68, 1.22-1.59, and 7.68-9.17 g·kg^-1, and the critical values were 15.09, 1.22, and 7.68 g·kg^-1, respectively. In low-yielding plantations, the nutrient diagnosis results from graph and index DRIS were identical, i.e., the nutrient requirement was P>N>K, which fitted with the background data of the nutrient contents in local soils. There were no correlations between the foliar nutrient contents and seed azadirachtin content, which was possibly due to the genetic factors of A. indica itself. Therefore, foliar nutrient diagnosis test could be not appropriate for measuring the seed azadirachtin content of A. indica seeding plantations.

Key words: semilethal low temperature (LT₅₀), cold resistance, anatomical structure.