An analysis of variability in the activity of nitrifiers in a soil under pasture, 1. Spatially dependent variability and optimum sampling strategy
1991
Bramley, R.G.V. | White, R.E. (Massey Univ., Palmerston North (New Zealand). Dept. of Soil Science)
Using a short-term nitrification assay (SNA) on samples from the field, the values of SNA, soil nitrate (NO3-N), and exchangeable ammonium (Ex-NH4) were all highly variable and conformed to lognormal distributions. The range of spatial dependence in the variability of SNA, NO3-N, and the pH of the SNA incubation media, which was assumed to approximate the field soil pH, was 3.3, 12.0 and 13.8 respectively. Ex-NH4 showed no spatial dependence. SNA, NO3-N and incubation pH varied isotropically within the sampling area, but soil moisture content was strongly anisotropic. The results are discussed in relation to the most efficient sampling strategy for estimation of the mean field nitrate concentration. Sufficient small localized clusters of samples should be taken to give a low standard error of the mean, with each cluster separated by at least 12 m.
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