Temporal fluctuations in soil test values under permanent pasture in New England, N.S.W

Abstract

Soil test P, K and pH were monitored on a monthly basis for two years in two P-rate grazing experiments on permanent pastures near Armidale, N.S.W. Highly significant fluctuations in time were observed for all soil tests at both sites. Components of variance derived from variance analyses indicated that temporal variation formed from 45-98% of the total random variance, depending on the soil test and site concerned. The relative magnitude of the temporal component did not vary substantially between fertilized and unfertilized plots. Correlation analyses did not establish any consistent association between soil test values and soil moisture index (SMI) or soil temperature, except for soil pH where positive and negative correlations, respectively, were found. Sampling efficiency analysis indicated that more than one sampling time would be required annually (or even bi-annually) to determine soil test means within acceptable confidence limits. Observation that the spatial component of variation was reduced in smaller plots suggests the use of small plots to monitor changes in soil fertility in large paddocks.