New Zealand Journal of Agricultural Research abstracts
Effect of lime on yield, N fixation, and plant N uptake from the soil by
pasture on 3 contrasting trials in New Zealand
D. M. WHEELER
D. C. EDMEADES
Ruakura Research Centre
New Zealand Pastoral Agriculture
Research Institute
Private Bag 3123
Hamilton, New Zealand
J. D. MORTON
Invermay Research Centre
New Zealand Pastoral Agriculture
Research Institute
Private Bag 50034
Dunedin, New Zealand
Abstract The amount of plant nitrogen (N) uptake from the
soil and fixed N in the herbage of clover species were measured using a
15N dilution technique on mowing trials at 3 lime rates (0, 5000,
and 10 000 kg/ha) at a low rainfall site (Matapiro soil) near Hastings over 5
years and at a high rainfall site (Mangatea soil) near Te Kuiti over 4 years.
At the low rainfall site, measurements were also made over 5 years on a grazing
trial at 2 lime rates (0, 7500 kg/ha). The dominant clover species was
subterranean clover on the low rainfall site and white clover on the high
rainfall site. Overall, the average proportion of clover N that was fixed from
the atmosphere (PNfix) was about 0.8 of total N in clover. The average annual
amount of fixed N in clover herbage was 35 kg/ha in the grazing trial on the
Matapiro soil, 65 kg/ha on the mowing trial and 105 kg/ha in the trial on the
Mangatea soil. Over all harvests and lime treatments, the amount of N fixed
could be estimated as 0.04 x clover yield (kg DM/ha) on the high rainfall
site and 0.046 x clover yield on the low rainfall site. The average annual
amount of plant N uptake from the soil by grass, clover, and weeds was 150
kg/ha in the grazing trial and 160 kg/ha in the mowing trial on the Matapiro
soil, and 240 kg/ha in the trial on the Mangatea soil. In the first 3 years,
lime increased grass N uptake by an average of 24 kg/ha/yr over all trials. In
the mowing trials, grass N uptake increased during the first 3 years by an
average of 16 kg/ha when 5000 kg/ha of lime was applied, and by 33 kg/ha when
10 000 kg/ha was applied. This increase was attributed to an increase in net N
mineralisation. However, the increase in net N mineralisation due to liming was
a short term effect as lime had no significant effect on grass N uptake after 3
years.
Keywords nitrogen fixation; 15N; isotope dilution;
nitrogen uptake; legumes; grazing; mowing; subterranean clover; white clover
New Zealand Journal of Agricultural Research, 1997, Vol. 40: 397-408
0028-8233/97/4003-0397 $7.00/0 (c) The Royal Society of New Zealand
1997
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