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How many soil samples are neccessary to obtain a reliable estimate of mean nitrate concentrations in an agricultural field?
Author(s) -
Ilsemann Jan,
Goeb Simone,
Bachmann Joerg
Publication year - 2001
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/1522-2624(200110)164:5<585::aid-jpln585>3.0.co;2-m
Subject(s) - sampling (signal processing) , environmental science , statistics , hydrology (agriculture) , agriculture , soil test , soil science , mathematics , soil water , geography , forestry , geology , physics , geotechnical engineering , detector , optics , archaeology
In Germany, field‐average soil NO 3 ‐ measurements are used to identify agricultural risks of groundwater pollution and to evaluate the compliance of land users with environmental regulations. In the present study, it was tested at three typical agricultural sites if common practices of soil NO 3 ‐ sampling were appropriate to obtain reliable estimates of the mean field NO 3 ‐ content in fall. Three sites of 1 ha area were extensively sampled for NO 3 ‐ . Ordinary statisticial analyses were conducted on the NO 3 ‐ data in order to calculate how many samples per ha were required to predict the mean field NO 3 ‐ with a given accuracy. Variograms were derived to assess applicability and relevance of ordinary statistical methods for heterogeneous fields. Results from statistical analysis suggest that at two sites common practices of soil NO 3 ‐ sampling would have been adequate to obtain estimates of the actual mean field NO 3 ‐ content with a sampling error less than 10 kg NO 3 ‐ ‐N ha —1 at a 95% probability level. At the other site, common practices obviously would have failed because NO 3 ‐ contents varied much more spatially. It remains a problem of soil sampling for NO 3 ‐ analysis that information on field heterogeneity is frequently not available a priori.