New Zealand Journal of Agricultural Research abstracts
Pasture response to soil phosphorus levels measured under mowing and dairy
grazing
J. D. MORTON
AgResearch Land and Environmental
Management
Invermay Agricultural Centre
Private Bag 50 034
Mosgiel, New Zealand
A. H. C. ROBERTS
AgResearch Land and Environmental
Management
Ruakura Research Centre
Private Bag 3123
Hamilton, New Zealand
Abstract Pasture responses to increasing soil Olsen P
(phosphorus) levels were measured under dairy grazing and mowing on an
allophanic soil (Egmont brown loam) in South Taranaki, New Zealand, for 4
years. Ten farmlet paddocks were allocated to each treatment with average
initial soil Olsen P (0-75 mm) levels of 29, 37, 45, 56, and 68 μg P
ml-1 and duplicate mowed plots sited on each of five paddocks. Mean
annual pasture production under grazing and mowing, respectively, increased
from 16.9 and 13.8 t DM ha-1 at the lowest to 17.6 and 15.0 t DM
ha-1 at the highest Olsen P. Average spring and autumn pasture P
concentrations increased from 0.33 to 0.38% under grazing and from 0.31 to
0.41% under mowing. Increasing Olsen P resulted in small non-significant
increases in average spring and autumn ryegrass contents in both grazing (56 to
63%) and mowing (42 to 45%) treatments. There was no effect of Olsen P on
average spring and autumn white clover contents in grazed pastures (8%) but a
small increase in mown pastures (8 to 12%). Fitting lines to describe the
relationship between Olsen P and the pasture parameters for 4 years grazing and
mowing data showed a significant difference (P < 0.05) in slope for
spring clover content only. However, there was a large variation in the slope
of the fitted lines between years. These results show that although there are
differences in absolute pasture production under mowing and dairy grazing, the
relative responses to P are not significantly different. Therefore, mowing
trials can be used to indicate relative responses in pasture production over
the Olsen P range typical of New Zealand dairy farms.
Keywords pasture; grazing; mowing; phosphorus; Olsen P;
production; P concentration; ryegrass; white clover
New Zealand Journal of Agricultural Research, 2001, Vol. 44: 259-268
0028-8233/01/4404-0259 $7.00/0 (c) The Royal Society of New Zealand
2001
PDF file of entire paper: medium quality (672K); (scanned from paper original: notes about this process)
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