Preliminary DRIS ratio norms for diagnosis of nutrient imbalance in Coorg mandarin

Abstract

The nutrient management strategies for rational fertilizer application were developed for Coorg mandarin through crop specific and reliable nutrient standards/norms using Diagnosis and Recommendation Integrated System (DRIS) technique. DRIS provided comprehensive leaf nutrient standards for diagnosis of nutrient imbalance for Coorg mandarin. DRIS is a dual ratio concept where the nutrient concentration ratios were considered rather than absolute nutrient concentrations in isolation. The diagnostic norms were essentially developed through a survey conducted in Kodagu region in Karnataka. The data bank of nutrient concentration vs. yield was divided into two sub-groups as low and high yielding based on the yield potential in individual orchards. The individual nutrient concentrations were expressed in as many forms as possible (e.g. N/P, N X P). The variance ratios and coefficient of variation were calculated for all forms of expressions. The nutrient expressions with high variance ratio and low coefficient of variation were chosen as diagnostic norms. Twenty eight nutrient expressions were derived for identification of nutrient imbalance in Coorg mandarin. Among the nutrient expressions selected as diagnostic norms for Coorg mandarin, some expressions such as N/P (6.427), N/K (1.703) and P/Zn (0.0134) were found to have greater physiological rationale in seedling plants. The ratio of N/P (7.17), N/K (1.395) and Zn/P (77.80) and Ca /Mg (5.92) were found important in budded plants. The nutrient imbalance in plants was diagnosed through DRIS indices. DRIS identified zinc and magnesium as the most yield-limiting nutrients.