add ml Stock solutions 10 ml MgSO4x7H2O (0.1g/100ml) 10 ml K2HPO4 (0.1g/100ml) 10 ml KNO3 (1.0g/ml) x ml Soilwater (depends on concentration) to distilled and autoclaved water to a final volume of 1 liter.
HEPES buffer: stock of 1M, adjusted to pH 7.5, end concentration in medium should be about 10-20 mM.