The relative effectiveness of various magnesium fertilisers on a magnesium-deficient pasture

摘要

Abstract Seven magnesium fertilisers—fine and coarse dolomite, fine and coarse dolomite-reverted superphosphate, magnesium phosphate, kieserite, and serpentine superphosphate—were compared against normal superphosphate in a field trial on a magnesium-deficient pasture. Equal amounts of Mg were applied in the first six magnesium fertilisers named. In the serpentine superphosphate treatment water-soluble Mg was approximately equal to total Mg in the other fertilisers. Highest yields were from the kieserite, serpentine superphosphate, and fine dolomite treatments. Based on pasture growth 3 cwt of serpentine superphosphate supplied the same amount of available magnesium as 1 cwt of fine dolomite. Two-thirds of the total Mg in the serpentine superphosphate appeared to be available for plant growth during the period of the experiment. Magnesium deficiency should be suspected on this soil when exchangeable Mg levels fall below 0.20 m.e. % or Department of Agriculture soil test values below 4.