Portable Xray fluorescence (pXRF) calibration for analysis of nutrient ...
Fertiliser samples for reference were ground to pass a 75microns mesh sieve on a Retsch PM400 planetary ball mill (Retsch , Germany). Dry powdered test samples ( ± g) were digested in graduated Pyrex tubes ... separated in sets of 5 g and milled on a Retsch PM400 ball mill 3 times for 6 min at 250 rpm. Between each of the 3 ...