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Abstract
Nutrient constraint based fertilizer schedule, following the leaf analysis in citrus orchards, is still not a common practice in India, due to absence of suitable leaf nutrient standards. An intensive survey of Nagpur mandarin orchards representing 17,799 ha (178 sq. Km) area in the hot sub-humid tropical climate of Central India, was carried out during 1992–98 to define nutritional problems and delineate optimum leaf nutrients level in relation to fruit yield of Nagpur mandarin (Citrus reticulata Blanco). Five to seven month old leaf samples between 2nd to 4th leaf positions from non-fruiting shoots and soil samples at 0–20 cm depth from 110–125 cm depth trunk, were collected, besides recording yield data. The leaf analysis values were observed better correlated with fruit yield in quadratic form than soil analysis except calcium (Ca) and magnesium (Mg). The optimum leaf nutrients concentration was determined as 2.2–2.4% nitrogen (N), 0.07–0.11% phosphorus (P), 1.2–1.6% potassium (K), 1.3–1.5% Ca, 0.48–0.67% Mg, 110–132 ppm iron (Fe), 29–43 ppm manganese (Mn), 8–14 ppm copper (Cu), and 18–30 ppm zinc (Zn) through multivariate quadratic correlation and regression analysis to obtain 636–703 fruits/tree. Based on above index values, N, K, Zn, Cu, and P were diagnosed as major nutrient constraints in mandarin orchards of Central India. These nutrients should be a part of fertilizer management.