New Zealand Journal of Agricultural Research abstracts
Sustainability of New Zealand high-country pastures under contrasting
development inputs. 4. Organic matter components
D. SCOTT
AgResearch
P.O. Box 60
Lincoln, New Zealand
Abstract Biomass, N, S, P, C, and Ca composition of shoots,
litter, roots and coarse organic matter >1.3 mm diam., and <2 mm soil
fraction are given for two trials under 61 different fertiliser and grazing
treatments on a Pukaki/Tekapo high-country soil after 10-15 years. Effects were
primarily related to fertiliser, secondarily to stocking rate, and rarely to
the grazing method. While there was an increase in soil C and N and a decrease
in C/N ratio of the <2 mm soil fraction with increasing fertiliser
rate, the relationships were weak. Spring shoot biomass increased with S and P
fertiliser rate and decreased with stocking rate. Surface litter (5-33 t
ha-1) was slightly greater under lax grazing, but total soil root
and coarse organic matter (6-57 t ha-1) increased with stocking
rate, with an exponential decrease with soil depth. There were only small
treatment effects on %N in organic components, %S in organic matter components
increased with S fertiliser rates, and %P increased with P fertiliser rates,
especially in the litter layer. There were active roots to 40 cm soil depth.
The half-life of leaf litter decomposition of 10 species from April to
September ranged from 0.2 to 38 years. The decomposition rate of litter was
positively correlated with C/N and Ca litter concentration over the first
fortnight after deposition and with %S in litter over the next 150 days.
Microbial biomass decreased with fertiliser level. An incubation experiment
indicated that nitrification was occurring. Grazing management treatments had
greater effects on soil organic components than on inorganic components.
Keywords New Zealand; high country; roots; sustainability;
organic matter; C; N; P; S; Ca
New Zealand Journal of Agricultural Research, 2000, Vol 43: 387-414
0028-8233/00/4303-0387 $7.00/0 (c) The Royal Society of New Zealand
2000
PDF file of entire paper: medium quality (5630K); (scanned from paper original: notes about this process)
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