Die Bodenkultur - Journal for Land Management, Food and Environment
R. ÖHLINGER, A. EIBELHUBER and M. VINZENZ:
Distribution and variation of soil enzyme activities in an uniform field and their influence on soil sampling and analysis
Surface soil samples of 1 ha plots (uniform soil type) of an arable land and of a grassland were taken according to a defined sampling pattern. The soil samples were analysed für protease activity (from fresh soil) and phosphatase activity (from air dried soil). The results were evaluated using different statistical techniques (classical and geostatistical):
- Changes of soil enzymatic activities were observed by storage at +4 °C (fresh soil) and at room temperature (air dried soil). After a period of 60 days phosphatase activity decreased by 30 % in arable land and by 16 % in grassland. In the same period grassland-protease was reduced of about 24 %. An internal standard is recommended to be carried along longer periods of analysis to correct a time dependent decline of enzyme activities.
Following sources of variance could be estimated (expressed as coefficients of variation): Analysis (including day to day variance) < 8 % for < 2mm sieving and about 17 % for <: 5 mm sieving.
Within field: protease 14 % (arable land and grassland), phosphatase 24 % (arable land).
Repeatability: < 5 % (< 2 mm sieving) and 10 % (< 5mm sieving).
Thus enzyme activities are determined best using the sieving fraction < 2 mm of fresh soil samples, For a uniform field of 1 ha a blended sample obtained from about 30 individual soil samples is optimal under the above conditions. By a triple analysis a precision of 10 % (P= 95 %) can be achieved.
Enzymatic activity (protease) was found to be spatially dependent within the field studied. The range of influence of one sample to another was approximately 40 meters, estimated by means of variogram calculation. Therefore a spatially dependent sampling can reduce the number of individual samples required to nine using a regular grid with 40 x 40 m.
Key-words: soil enzymes, soil sampling, spatial distribution, statistic.