Effects of calcined magnesite,magnesium hydroxide and “geosan” on soil properties in declining spruce stands (NE Bavaria)

The results of pH-stat.-titrations at six pH levels show increasing reactivities of the fertilizers under investigation in the order magnesite < Geosan < Mg-hydroxide. Further differences exist in the acid neutralization capacity of the three samples. By 3 mo after fertilization, Mg concentrations in soil solution down to 70 cm soil depth significantly increased. Differences between the fertilizers reflect their reactivities. Fertilization increases soil nitrate concentrations by 50 to 100% up to 55 ppm. It is unclear why the control plots already show high nitrate contents in soil solution. The top mineral soil shows significant increases of base saturation after fertilization. The highly reactive Mg-hydroxide produces the highest Mg concentrations in the soil solution, whereas the slower soluble magnesite has a stronger effect on the exchange complex.