3 April 1998

A powder for staggers

SPRAYING pastures with magnesium hydroxide could prove to be a more effective way to control grass staggers than dusting with calcined magnesite, with reduced levels still persisting after at least seven days grazing and rainfall.

Thats according to Jim Parkins of the University of Glasgow who has been examining availability and effectiveness of varying rates of application.

Higher magnesium

He explained that magnesium hydroxide powder has been demonstrated to have a higher magnesium availability than some granular calcined magnesites.

Pasture dusting with fine particle grade calcined magnesite at 16kg/ha magnesium does prevent staggers, but almost double the rate is needed for practical use as spreading distribution and its ability to stick to the leaf may be inefficient.

To find a more practical alternative, Prof Parkins carried out grazing trials using magnesium hydroxide diluted with water and applied at different rates by grassland sprayer to pasture.

The spray adhered well to grass and there were no apparent effects on herbage palatability or pattern of grazing by cows or ewes. Over two trial years a similar rainfall of 15mm (0.6in) was recorded between days three and seven after application.

Efficient method

Prof Parkins believed that liquid magnesium hydroxide, applied at the rate of 5kg magnesium/ha was an efficient way to provide supplementary magnesium to milking cows at cows and ewes with twin lambs over critical spring grazing periods.