ScienceAsia 5 (1979): 145-156 |doi: 10.2306/scienceasia1513-1874.1979.05.145

LEAF AGE INDEX: A PARAMETER FOR THE STAGE OF DEVELOPMENT.
A BASIS FOR THE QUANTITATIVE MODELS FOR THE EVALUATION AND CONTROL OF NUTRITIONAL STATUS OF RICE

A.K. ALVA^* and S.W. BILLE

Summary: This paper presents an attempt to transfer a new fertilization system developed in Denmark to rice crop in Thailand. Fertilizer experiment with varying amounts of N, P, K and N topdressing was conducted in a growth chamber by simulating the climatic conditions prevailing in Central Plain of Thailand. Rice variety RD-1 was used for the study. The concentrations of N, P, K, Ca, Mg and Na were determined in the aboveground portion of the plants at different intervals during the growing period and at maturity.

          The concept of Leaf Age Index (LAgI) was introduced to examine the possibilities of using this parameter for defining the stage of development. It was found that although LAgI is supposed to represent a uniform stage of inner development and it is rather clear to identify, its application as an expression of the stage of development was unsuitable. primarily due to ambiguous and nonreproducible relationships between grain yield and concentration of a nutrient at different LAgI and also due to diffic.ulties in identifying a stage of development (in terms of LAgI) corresponding to which the interaction between various nutrients is minimum.

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Department of Soil Fertility and Plant Nutrition, Royal Veterinary and Agricultural University Copenhagen, Denmark

Received 11 July 1979