New Zealand Journal of Agricultural Research abstracts
Pasture responses to phosphorus and nitrogen fertilisers on East
Coast hill country: total production from easy slopes
A. G. Gillingham*
AgResearch
Palmerston North
J. D. Morton†
AgResearch
Mosgiel
M. H. Gray‡
AgResearch
Havelock North
*Present address: Research Consultant, 92 Waicola Drive,
RD1, Palmerston North 4471, New Zealand. a.gillingham@xtra.co.nz
†Present address: Ballance-Agri-Nutrients, PO Box 65,
Rolleston, Christchurch 7643, New Zealand.
‡Present address: Maurice Gray and
Associates Ltd, 1 Aotea Crescent, Havelock North 4130, New Zealand.
Abstract A series of small, mowed plots,
excluded from grazing, were established on flat to easy sloping (up to
15°) pastures on farms from Wairoa (northern Hawke's Bay) to
Moeraki (North Otago) with contrasting degrees of spring, summer and
autumn dryness, to evaluate the pattern of pasture responses to a range
of nitrogen (N) fertiliser rates, and associated soil phosphorus (P)
levels. Mean annual rainfall ranged from 474 (Marlborough) to 1348 mm
(Wairoa) with all farms having an associated range in
spring/summer/autumn rainfall. In mid–late winter 2000, fertiliser P
and N were applied at 0, 30, 60 or 90 kg ha–1 in a
completely randomised design with incomplete replication. In winter
2001 and 2002 the rates of N fertiliser (urea) treatments were
repeated. The application of P fertiliser (triple super) varied between
treatments, sites and years in an attempt to generate and stabilise a
range of soil P tests at each site. The rates of P applied in 2001 and
2002 were based on the soil Olsen P test in the previous spring. The
pasture response to N fertiliser differed between the early spring
(August–October) and late spring–autumn seasons. The pasture response
in early spring to N fertiliser ranged from 1.58 kg DM kg–1 N
in Marlborough to 17.9 kg DM kg–1 N fertiliser at Wairoa.
Conversely, at almost all sites, there was a negative pasture response
in late spring–autumn to increasing rate of N fertiliser. The net
difference between the positive pasture responses to fertiliser N in
early spring and the negative effects in late spring–autumn showed a
positive net response over the total season. The overall average for
all sites was 12.4 kg DM kg–1 N response at the 30 kg N ha–1
rate, and 7.6 kg DM kg–1 N fertiliser at the 90 kg N ha–1
rate. The relative pasture responses at most sites to increasing
soil P status was similar in both the early spring, and in the late
spring–autumn seasons. Asymptotic regression relationships
(Mitscherlich type), derived for data from each of the Wairoa,
Puketapu, Waipawa, Wallingford and Moeraki sites suggested that near
peak responses were obtained at Olsen soil P test of 20.
Keywords hill country; nitrogen fertiliser;
pasture production; phosphate fertiliser
A06035; Online publication date 3 July 2007; Received 29 May 2006;
accepted 12 May 2007
New Zealand Journal of Agricultural Research, 2007, Vol. 50:
307–320
0028–8233/07/5003–0307 © The Royal Society of New Zealand 2007
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