Diagnostic leaf nutrient norms and identification of yield limiting nutrients in gerbera grown under protected conditions using DRIS

By using DRIS, the whole population was divided into two sub-groups and identified forty-five nutrient expressions as diagnostic norms from the data collected on macro- and micronutrients of leaves through survey of protected cultivation units of gerbera. These expressions had shown higher variance and lower coefficient of variation that are found to have greater diagnostic precision viz., P/N (0.061), N/K (0.715), N/S (12.795), P/S (0.775), S/K (0.056), Fe/Mn (2.767), Zn/Mn (0.746), etc. The overall imbalance of the nutrient was assessed based on sum of the indices irrespective of sign. Higher the sum value, larger will be the plant nutritional imbalance that is indicated by nutritional balance index (NBI). The diagnosis of nutrient imbalance through DRIS indices indicated that potassium and zinc were the most yield-limiting nutrients in gerbera. In addition, five nutrient ranges were derived using mean and standard deviation as low, deficient, optimum, high and excess for each nutrient to serve as a guide for diagnostic purpose. The optimum leaf N ranged from 2.54 to 2.87%, P from 0.13 to 0.16%, K from 3.37 to 4.37%, Ca from 1.45 to 1.99%, Mg from 0.56 to 0.74% and S from 0.17 to 0.22%. Among the micronutrients, the optimum iron concentration in the leaf ranged from 225 to 287 ppm, Mn from 88–126 ppm, Zn from 56 to 85 ppm and Cu from 17 to 32 ppm. These leaf nutrient standards can be used for efficient fertilizer programming and to correct the nutrients in question for obtaining good flower yield and quality flowers under protected conditions.