Recommended rates of potash for grazed grass are 60kg/ha and 30kg/ha of K2O for soil index 0 and 1 respectively. For soils with higher soil fertility levels no potash required.
Very large quantities of potash are removed in grass silage which must be replaced to maintain soil fertility and yield potential. The following is guide to typical potash offtakes from multi-cut silage systems.Low soil magnesium levels will affect grass yield as well as mineral balance in the animal. Apply 50-100 kg/ha MgO every three to four years at Mg index 0. Yield response is less certain at index 1 but magnesium application is justified in terms of insurance for grass yield and mineral balance for the animal, to maintain a soil magnesium index of 2.
Where lime is required and Mg levels are 0 and 1, use magnesian limestone as the most cost effective magnesium source. Where pH is satisfactory, specific magnesium fertilisers (see table below) should be used for soil improvement. Use water soluble forms of magnesium where rapid plant uptake is required.
