New Zealand Journal of Agricultural Research abstracts
Relationship between pasture dry matter yield and soil Olsen P from a series of
long-term field trials
A. G. SINCLAIR*
P. D. JOHNSTONE
L. C. SMITH
AgResearch, Invermay Agricultural Centre
Private Bag 50034
Mosgiel, New Zealand
A. H. C. ROBERTS
M. B. O'CONNOR
AgResearch
Ruakura Agricultural Research Centre
Private Bag 3123
Hamilton, New Zealand.
J. D. MORTON
AgResearch, Invermay Agricultural Centre
Private Bag 50034
Mosgiel, New Zealand.
Abstract Forty-six data-sets from a series of 17 long-term
field trials measuring the effects of rates and forms of phosphate (P)
fertiliser on pasture production and soil fertility in New Zealand were used to
characterise the relationship between pasture dry matter (DM) yield in any year
(expressed as relative yield, RY) and soil Olsen P test at the end of the
annual DM measurement period. Average coefficients of variation in the
measurement of these parameters were 7% and 17% for DM yield and Olsen P,
respectively. The results failed to demonstrate that the RY at any site
in any year could be reliably assessed from a common relationship between RY
and the Olsen P test. However, the mean relationship did take the general
"diminishing returns" form as expressed by the Mitscherlich equation, and as
Olsen P levels increased the probability of low RY decreased. There was no
evidence that RY increased with increase in Olsen P test values above 20, with
the exception of the one yellow-brown pumice soil in the series.
The largest component of variability in the RY v. Olsen P relationship
occurred within years within individual sites, reflecting inherent within site
variability and treatment and measurement errors. Variability was also large
between years within sites; this appeared to arise from erratic patterns of
response within sites over time, possibly because of climatic, botanical, and
edaphic fluctuations. The least variability in the RY v. Olsen P relationship
arose from differences between sites. Soil pH, P retention, and rainfall did
not significantly affect the relationship, but the yellow-brown pumice site and
sites with high DM production gave lower RY for any given Olsen P than other
sites.
Keywords Olsen test; P fertilisers; pasture yield; relative
yield; response curves; soil P test; triple superphosphate
New Zealand Journal of Agricultural Research, 1997, Vol. 40: 559-567
0028-8233/97/4004-0559 $7.00/0 (c) The Royal Society of New Zealand
1997
PDF file of entire paper: medium quality (724K); (scanned from paper original: notes about this process)
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