New Zealand Journal of Agricultural Research abstracts
Effects and interactions of phosphorus and sulphur on a mown white
clover/ryegrass sward
3. Indices of nutrient adequacy
A. G. Sinclair
J. D. Morrison
L. C. Smith
K. G. Dodds
AgResearch
Invermay Agricultural Centre
Private Bag 50034
Mosgiel, New Zealand
Abstract Relationships were examined between relative yields
of pasture with respect to phosphorus (P) and sulphur (S) applications, and
clover herbage P and S concentrations and P/nitrogen (N) and S/N ratios in a
P x S factorial fertiliser trial on a mown clover/ryegrass sward. The
relationships between the yield of a treatment relative to the maximum yield
obtainable with high rates of P alone (RY[P]) and both % P and P/N were
affected by the application rate of S. S deficiency generally lowered the % P
required for any given RY[P] but raised the P/N required. This latter effect
was because S deficiency markedly lowered clover herbage N concentration. P
deficiency had a similar but smaller effect on % S and S/N required for any
RY[S]. S/N was much less sensitive to changes in clover S status than P/N was
to changes in clover P status. This resulted from the strong stimulatory effect
of S on clover % N. Relationships were also established between clover P and S
adequacy indices and RY[PS] which is the herbage yield with P and S in
physiological balance relative to the maximum yield with P and S in
physiological balance. These relationships differed from those involving RY[P]
and RY[S], requiring a higher value of the adequacy index for any specified RY.
Nutrient concentrations (particularly of S and N) and ratios changed during a
year, indicating that more than one sampling per year would be necessary to
determine whether the current fertiliser policy was succeeding in maintaining
adequate and balanced nutrition throughout the year.
Keywords critical nutrient concentrations; fertiliser;
nitrogen; nutrient indices; nutrient ratios; pasture; phosphorus; plant
analysis; relative yield; sulphur; white clover
New Zealand Journal of Agricultural Research, 1997, Vol. 40: 297-307
0028-8233/97/4002-0297 $7.00/0 (c) The Royal Society of New Zealand
1997
PDF file of entire paper: medium quality (675K); (scanned from paper original: notes about this process)
This year's abstracts |
Journal home page |
All abstracts |
Publishing home page
