In:
Soil Research, CSIRO Publishing, Vol. 38, No. 1 ( 2000), p. 85-
Abstract:
Changes in soil properties in response to cropping pressure were measured in 2
mineralogically contrasting New Zealand topsoils. Waiareka clay (Vertic Haplustoll) with 〉 65% smectite clay was compared with Wakanui silt
loam (Aquic Haplustept), which contains about 20% mixed or illite clays. Soil properties (0–10 cm) were assessed by changes in organic
carbon (C) and nitrogen (N), pH, cation exchange capacity, Olsen P, microbial C, soil respiration, microbial functional evenness, mineralisable N, bulk
density, unsaturated hydraulic conductivity, readily available and total available water, macro porosity and total porosity, particle density, and
particle size distribution. Additional samples of the Waiareka clay soil were taken at 10–20 cm depth. Cropping pressure was estimated using a scale
based on the number of years in crop v. those in pasture.
The organic and biological status of the Waiareka pasture soil (0–10 cm) was greater than that of the Wakanui pasture, with contents of 5.1%
organic C, 0.43% total N, 1429 microbial C (µg/cm3), and 123 mineralisable N
(µg/cm3), compared with values of 4.0%, 0.31%, 795 µg/cm3, and 89
µg/cm3, respectively. Total and macroporosity, and total and readily available water, were also greater on the Waiareka
pasture soil compared with the Wakanui pasture soil. Under cropping pressure, the Waiareka soil had marked declines in organic matter C and N, microbial C
and soil respiration, microbial functional evenness, macroporosity, and available water. In contrast, the Wakanui silt loam showed little response to
cropping pressure; mineralisable N declined slightly and particle density increased under cropping.
We concluded that the initial properties of a soil were not good predictors of subsequent resistance to cropping pressure; and that soils with initially high
status have the potential for proportionally greater decline.
Type of Medium:
Online Resource
ISSN:
1838-675X
Language:
English
Publisher:
CSIRO Publishing
Publication Date:
2000
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