Abstract:
CuStivar-based nutrient diagnostics are widely used for identifying nutrient deficiencies
in commercial citrus orchards. But, the precision of diagnosis is limited by the interpretation
tools used in establishing the diagnostic limits. Two commonly used interpretation
tools, MQRA and DRIS were tested for their diagnosis, and found to predict
different optimum limits. DRIS-foased analysis showed optimum values as: 2.52-2.61%
N, 0.04-0.05% P, 1.63-1.82% K, 1.32-1.48% Ca, 0.10-0.18% Mg, 214-308 mg/kg Fe, 92-
110 mg/kg Mn, 9-12 mg/kg Cu and 9-12 ppm Zn in relation to fruit yield of 9-11 tons/
ha/year, while MQRA established the optimum values as : 2.28% N, 0.06% P, 1.68%
K, 1.28% Ca, 0.13% Mg, 252 mg/kg Fe, 84 mg/kg Mn, 5 mg/kg Cu, and 10 mg/kg Zn
for optimum fruit yield of 7 tons/ha/year. Due to diagnostic values varying in their optimum
limits, two statistical models diagnosed contrasting nutritional problems. These
observations suggest that two different sets of nutritional problems could be diagnosed
if the same set of leaf analysis data is subjected to different interpretation tools. However,
DRIS values were further observed much nearer to high performance orchards
compared to MQRA. All the orchard sites were diagnosed with the multiple deficiencies
of nutrients like Zn > P > Ca > Mg > N > Cu in decreasing order.
