József Prokisch, Dóra Hovánszky, Éva Széles, Béla Kovács, Zoltán Győri University of Debrecen, Centre of Agricultural Sciences, Institute of Food Science, Quality Assurance and Microbiology 4032 Debrecen Böszörményi út 138. Hungary Inhomogeneity of the agricultural soils in Hungary Basic terms: Homogenous, heterogenius, inhomogenous Inhomogenity, Guide to the expression of uncertainty in measurement (GUM) Representative sampling Question of this study: What is the real inhomogeneity of our soils in the practice?

The scale and the inhomogeneity

JPconv.exe

The scale and the measured inhomogeneity

Questions of this study 1.How many sample should I take from an arable field for getting results with a certain confidence level? 2.Who is responsible for the uncertainity? Sampling or the laboratory? What is the acceptable uncertainity of a repeated measurement of soil from an arable field (5- 30 ha) 35.6 ± 12.5 mg/kg 25.3 ± 5.2 mg/kg 45.6 ± 22.5 mg/kg An example:

The sampling site and sampling strategy Example: Nádudvar, Hungary, 47 o 26’36.8”N 21 o 13’37.9”E 1000 m * 300 m = 30 ha 147 sample Measured parameters: pH, CaCO 3, N, P, K, „total” and „plant available” metals, pesticides

Cr („total”) [mg/kg] (ICPOES) 1000 m * 300 m = 30 ha 147 sample Cost more than 6000€ Al („total”) [mg/kg] (ICPOES) Results: Spatial distribution of total aluminum and chromium in the soil at the sampling site

P („total”) [mg/kg] (ICPOES) P („Ammonium lactate soluble”) [mg/kg] (Photometry) 1000 m * 300 m = 30 ha Spatial distribution of total and AL soluble phosphorous in the soil at the sampling site

The developed and applied Monte-Carlo model for the sampling Random selection of certain number of sample Calculation of average Repeating 100 times Calculation of relative standard deviation of average values

P Cr Results of the Monte-Carlo model

Conclusions Comparison of standard procedures and practical results 5 ha = 1 sample (what was created by mixing individual point) 30 ha = 6 sample (60 sample) A repeated procedure should produce a results less than 3 % RSD% for the phosporous and less than 1 % for chromium. 1 or not enough sample  can resulted high uncertainity Correct sampling  acceptable uncertainity  reason of high uncertainity (>10%) in the land scale sampling is caused by the wrong measurement in the laboratory or very high antropogenic contamination Good sampling is not impossible!

Thanks for you attention!