In Greenland vast amounts of glacial sediment is flushed out with meltwater from melting landbased glaciers. It is deposited in estuaries, lakes, in the ocean and all along the Greenlandic coast in distinct size fractions. The finest of the material (<200μm) is considered glacial rock flour (GRF). Countries with high agricultural productivity are mainly located in the floodplains of former ice ages. Soils in these regions are younger than those found in the tropics, with exceptions of tropical soils affected by recent tectonic or volcanic alterations. Applying GRF to weathered or nutrient poor soils could be an artificial way of rejuvenating them, potentially increasing fertility and yield of otherwise poor soils. Even under intensified agricultural conditions such as in Denmark, GRF could serve as an alternative nutrient source in certified organic production. Organic farmers urge to become independent of conventional inputs and especially meeting potassium demands is challenging with existing resources. There is an interest in possibilities for remineralizing potassium in soil using GRF. This PhD thesis covers work on evaluating the potential for using GRF as a soil amendment to weathered tropical soils and sandy Danish soils. Much emphasis was put on the plant nutritional benefits of GRF. The work included climate chamber and greenhouse pot experiments, field trials, soil incubation, lab work and field work in both Greenland and Denmark. Although not unravelling all the potential beneficial effects of GRF, the conclusions from the conducted work are very promising with consistent positive effects of GRF from lab to field scale. Through rapid weathering of GRF in active soil environments and high doses of application, GRF can increase biomass of plants. Potassium and small amounts of magnesium are supplied to soils and plants from GRF. Although not an essential nutrient, plants also benefit from silicon supplied from GRF.