Cc. Boswell, DRYLAND LUCERNE RESPONSES TO ELEMENTAL SULFUR OF DIFFERENT PARTICLE SIZES APPLIED AT DIFFERENT RATES AND FREQUENCIES IN NORTH-OTAGO, NEW-ZEALAND, New Zealand Journal of Agricultural Research, 40(2), 1997, pp. 283-295
Elemental sulphur (S) of three particle sizes (< 150, 250-500, and 100
0-2000 mu m), screened S (a product with a range of particle sizes), a
nd gypsum (a sulphate fertiliser) were each applied to lucerne pasture
at 25, 50, 100, and 200 kg Siha in a dry inland environment. Pasture
deficiencies first developed during the second year after fertiliser a
pplication. Oxidation rates of the elemental S particles were measured
directly from the residual elemental S in the soil and indirectly by
soil and plant S analyses. Particles < 150 mu m were 90% oxidised with
in 1 year of application and are best suited to annual applications; p
articles of 250-500 mu m were oxidised over about 3 years, and were su
ited to biennial or triennial application; particles of 1000-2000 mu m
were very slowly oxidised and were not recommended as fertilisers. Sc
reened S was broadly comparable with 250-500 mu m elemental S. Gypsum
was an effective fertiliser form for lucerne in this environment. S in
puts required for maintenance of both lucerne pasture production under
a cut and removal (haying) management, and soil sulphate reserves, we
re about 25 kg S/ha per year in an available form.