Development of Nutrient Diagnostic Technique for Khasi Mandarin (Citrus reticulata Blanco) Grown in Manipur

Importance of optimum soil fertility and plant nutrition in sustaining the citrus orchard performance is well known. Extensive surveys were carried out covering as many as 40 orchards of Khasi mandarin in Thangal village of the sub-division Nungba under Tamenglong district in the year 2010–2011. DRIS-based analysis predicted the optimum values of available nutrients in soil as: N 142.4–222.3%, P 5.9–8.2%, K 110.5270.3%, Ca 152.4–281.3%, Mg 28.3–79.4%, Fe 32.4–49.2 ppm, Mn 26.6–41.1 ppm, Cu 0.89–1.4 ppm and Zn 1.2–2.4 ppm in relation to fruit yield of 28.2–49.6 kg tree⁻¹. The developed DRIS indices predicted optimum value of different leaf nutrients as: 1.86–2.62% N, 0.08–0.10% P, 0.89–1.86% K, 1.62–2.12% Ca, 0.40–0.50 Mg, 119.4–219.4 ppm Fe, 58.7–84.7 ppm Mn, 2.2–3.3 ppm Cu and 20.8–29.8 ppm Zn in relation to fruit yield of 28.2–49.6 kg tree⁻¹. Nutrient constraints in the form of N, P, Ca, Mg, Cu and Zn were identified using these diagnostics which must find a due place in a fertilizer program of mandarin orchards in the region to obtain optimum fruit yield on sustained basis. Various nutrients in the order of decreasing influence on fruit yield were rated as: Zn < P < Ca < Mg < N < K < Fe < Mn < Cu through leaf analysis. While through soil analysis, DRIS indices revealed different nutrients in the decreasing order of their influence on fruit yield as: Ca < Mg < P < Zn < N < K < Cu < Mn < Fe.