Diagnosis of Nutrient Imbalance in Mango by DRIS and PCA Approaches

Abstract

Nutrient concentration in Totapuri cultivar of mango leaf as affected by application of varying levels of nitrogen (N), phosphorus (P), or potassium (K) was monitored in three field experiments for a period of nine years from 1991 to 1999. A data bank of nutrient concentration vs. fruit yield was established based on the mean nutrient concentration determined for different treatments. The data was further sub-divided into low and high yielding population based on yield performance. The Diagnosis and Recommendation Integrated System (DRIS) ratio norms were developed from high yielding population, while diagnosis of nutrient imbalance was made in low yielding plants. Forty-five nutrient expressions were chosen as diagnostic norms. Not withstanding application of a wide range of major nutrient doses, fruit yield was low in four to five cropping seasons. DRIS indices showed no signs of improvement nor there was a trend with application of N, P, or K at different levels. Some measures of total imbalance of nutrients in plant were reflected through sum of DRIS indices irrespective of sign. The greater imbalance of nutrients resulted in lower fruit yield. Principal Component Analysis (PCA) was applied to extract the correlation structure among the nutrient in low and high yielding plants and for DRIS indices. The first PC derived by PCA performed both on absolute nutrient concentration and DRIS indices was designated as (N−P + Mg−S + Fe + Cu+). Involvement of several nutrients in a single PC indicated that, it was not possible to diagnose nutrient imbalance of any particular nutrient in isolation in fruit crops like mango. The nutrient concentration variation in mango leaf appears to be an overall orchard phenomenon rather than individual tree phenomenon.