Spatial variability of biochemical properties in a taxonomically-uniform soil under grazed pasture

Spatial variability in levels of three chemical and twelve biochemical properties was measured in samples of a Typic Haplaquoll taken from a small, uniform site under grazed pasture. Three separate comparisons were made between: ten small samples to assess topsoil variability, two sets of adjacent cores to assess short-range variability, and six samples taken at different depths down the soil profile. A method for estimating xylopyranosidase activity is also given.Properties generally differed significantly among the topsoil samples, with biochemical variability being often significantly greater than chemical variability. The sample sizes required to estimate the site means, with a standard error of 5%, were calculated for each property; they ranged from 44 for urease activity to 3 for organic C content and invertase activity. Most biochemical activities were positively and significantly correlated with soil organic C and total N contents. Respiratory activity, however, was correlated significantly only with soil moisture. There were few highly-significant relationships between enzyme activities. Exceptions were the very significant relationship between urease and sulphatase activities, and the significant correlations of phosphatase activity with all other enzyme activities except xylanase.Values of chemical properties in adjacent cores were very similar within each set, but biochemical properties often varied considerably. One set of samples was generally more variable than the other.All properties showed the expected decline with soil depth. Biochemical activities declined more rapidly than organic C and total N contents, and were clearly influenced by factors additional to organic matter content.Recommended sampling procedures are given for seasonal or soil characterization studies.