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Table 4 Predictive regression equations and physical and economical optimal doses of N and K under different agro-climatic conditions

From: Crop-ecology and nutritional variability influence growth and secondary metabolites of Stevia rebaudiana Bertoni

Experimental site Plant nutrient Regression equation Physical optima (kg ha −1 ) Economical optima (kg ha −1 )
CSIR-IHBT Nitrogen y = 0.795 + 0.0192*x − 0.00009*x2 106.67 106.16
Potassium y = 0.89 + 0.0358*x − 0.0004* x2 44.62 44.43
RHRS Nitrogen y = 0.705+ 0.005*x − 0.000006* x2 - -
Potassium y = 0.665 + 0.0159*x − 0.0002* x2 39.75 39.37
PAU Nitrogen y = 0.17+ 0.0134*x − 0.00009* x2 74.44 73.93
Potassium y = 0.55 + 0.0036*x − 0.00004* x2 45.00 43.08
  1. *mark indicates that the corresponding values are significant at P = 0.05 . The physical and economical optima of N for RHRS were not calculated since the relation between N and dry leaf yield (t ha−1) was almost linear.