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The phosphorus requirements for silage production on high fertility soils
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2005
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IJAFR 44p281.pdf
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V. Power, H. Tunney and D.W. Jeffrey. The phosphorus requirements for silage production on high fertility soils. Irish Journal of Agricultural and Food Research, 2005, 44, 281-296
Abstract
The minimum phosphorus requirement for a mid-season ryegrass was investigated
under cutting conditions over a 10-year period at each of three Teagasc sites
(Clonroche, Johnstown Castle and Oak Park) in southeast Ireland. Treatments consisted
of 0, 20, 30, 40, and 50 kg ha–1 year–1 P applied in autumn. Generally, there were
three grass cuts each year and soil samples were taken after the third cut prior to the
application of P. Nitrogen and potassium fertiliser was applied to ensure maximum
grass yield. There was an emerging treatment effect over time as evidenced by the
significance of the treatment × year interaction. The effect of site varied with year
reflecting the variability in weather and number of cuts taken at the individual sites. A
treatment effect on annual first-cut-silage yield was observed. The largest treatment
difference for dry matter (DM) yield of first-cut silage was between the control and the
P treated plots (0.32 t/ha). The results show that the draw down of soil-P reserves was
adequate to maintain yield for a number of years without additional fertiliser P application.
Initial soil tests indicated moderate to high soil test P levels (STP) as measured
by the Morgan’s test. Application of P at equivalent to removal rates did not maintain
STP. The results suggest that application of a regular small maintenance dressing of P,
replacing realistic removals, is the most appropriate fertiliser application strategy.