New Zealand Journal of Agricultural Research abstracts
Effect of serpentine rock and its acidulated products as magnesium
fertilisers for pasture, compared with magnesium oxide and Epsom salts,
on a Pumice Soil. 1. Dry matter yield and magnesium uptake
J. A. Hanly
P. Loganathan
L. D. Currie
Fertilizer and Lime Research Centre
Institute of Natural Resources
Massey University
Private Bag 11 222
Palmerston North, New Zealand
J.A.Hanly@massey.ac.nz
Abstract Low pasture magnesium (Mg) intakes by
grazing dairy and beef cows is a main cause of hypomagnesaemia in these
animals soon after calving. Magnesium fertiliser application to pasture
can increase pasture mixed-herbage (hereafter “herbage”) Mg
concentration and reduce the risk of this disorder. However, the
effectiveness of Mg fertilisers is variable depending on fertiliser
type and soil properties. A 32-month Mg fertiliser field trial was
conducted on dairy pasture on an Immature Orthic Pumice Soil (near
Taupo, New Zealand; exchangeable Mg 0.4 cmol
c kg
–1,
pasture Mg 0.13%) to compare the effectiveness of a range of Mg
fertilisers in elevating herbage Mg concentration. The fertilisers used
were ground serpentine rock, three acidulated serpentine rock products,
Epsom salts, and E-mag (magnesium oxide). All fertilisers were applied
at 100 kg Mg ha
–1 at the start of the
trial. The trial also had two treatments where Epsom salts was applied
at 25 and 50 kg Mg ha
–1 and a treatment
where serpentine rock was reapplied during the second and third year at
100 kg Mg ha
–1. Magnesium fertiliser
treatments did not affect pasture dry matter yield significantly at any
harvest, however, the effect of treatments on herbage Mg concentration
was highly significant (
P < 0.001)
at all harvests. The single application of serpentine significantly
increased herbage Mg concentration at 10 harvests, with five of
these harvests having Mg concentrations
≥0.20%, which is generally
considered to be the minimum “threshold level” for stock health. In
comparison, the Mg concentration in pasture not receiving Mg fertiliser
remained below the minimum threshold level throughout the trial.
Application of serpentine rock annually further increased herbage Mg
concentration and accumulation. The herbage Mg concentrations for this
treatment were similar to those of the Epsom salts (50 kg Mg ha
–1)
treatment at the majority of the harvests. These results indicate that
the annual application of serpentine rock may have potential as an
alternative strategy to the application of more soluble Mg sources for
raising herbage Mg concentration to levels considered adequate to meet
stock health requirements. The more soluble Mg fertilisers—Epsom salts,
the two serpentine-superphosphate products, and an acidulated
serpentine rock plus reactive phosphate rock product—had the greatest
effect on increasing herbage Mg concentration and accumulation. These
treatments increased herbage Mg concentration to
≥0.20% within
3–6 months after application and for the majority of harvests over
the rest of the trial period. The effect of E-mag on herbage Mg
concentration was similar to that of serpentine rock during the first
year, but the subsequent performance of E-mag was similar to the more
soluble Mg fertilisers.
Keywords dairy pasture; fertiliser;
hypomagnesaemia; magnesium; Pumice Soil; serpentine
A05013; Received 8 April 2005; accepted 1 September 2005; Online
publication date 11 October 2005
New Zealand Journal of Agricultural Research, 2005, Vol. 48:
451–460
0028–8233/05/4804–0451 © The Royal Society of New Zealand 2005
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