New Zealand Journal of Agricultural Research abstracts
Sustainability of New Zealand high-country pastures under contrasting
development inputs. 5. Nutrient pools and balances
D. SCOTT
AgResearch
P.O. Box 60
Lincoln, New Zealand
Abstract The nutrient fluxes, pools, and balances for N, S,
P, and Ca were estimated for two sheep-grazed mixed species studies on a
Pukaki/Tekapo high-country soil from measurements during the 10-15th years
following initial development. One compared 30 combinations of 5 superphosphate
rates (0-500 kg ha-1 yr-1) x 3 stocking rates x 2
stocking methods x 2 spatial replications; the other compared 27 combinations
of P and S fertiliser (0-100 kg element ha-1 yr-1). The
stock off-take under zero fertiliser was 1.1, 0.1, 0.2, and 0.4 kg
ha-1 yr-1 for N, S, P, and Ca, respectively. Fertiliser
inputs exceeded stock off-takes by 4-100-fold in fertiliser treatments. The
10-year stock off-take was similar to the 1-year spring shoot pool. C and N
were principally in the soil fraction. Estimated N fixation was 150-223 kg N
ha-1 yr-1 in the fertilised treatments. Increases in the
components of the S pools in the shoots and soil to 40 cm accounted for 46-56%
of the applied S in the dryland fertilised treatments and 21% in the irrigated
high fertiliser treatment. Residual elemental S accounted for 11-21% of applied
S. Much of the P and Ca were in the coarse organic matter pools. P and Ca pools
did not increase in proportion to fertiliser rates. There was an apparent loss
of total P to levels similar to double the applied fertiliser rates, possibly
from change in datum sampling depth due to measured soil expansion. There was
less than 2% movement of nutrients into sheep camps.
Keywords New Zealand; high country; Ca; sustainability;
nutrient balance; N; S; P
New Zealand Journal of Agricultural Research, 2000, Vol 43: 415-438
0028-8233/00/4303-0415 $7.00/0 (c) The Royal Society of New Zealand
2000
PDF file of entire paper: medium quality (4735K); (scanned from paper original: notes about this process)
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