Sampling and analytical methods for the determination of available soil nitrogen in Austria

Nitrogen nutrition of field-grown vegetables needs to find a balance between achieving maximum yield, whilst minimising leaching. One possible approach is to determine nitrogen or other soil parameters in order to predict the nitrogen fertilizer requirement of the plant. Correct sampling techniques and suitable analytical methods are therefore of great importance to both goals. Soil analytical methods can determine either the relevant soil nitrogen status or try to predict the mid-term availability of nitrogen. The nitrogen status is usually determined by soil mineral nitrogen (SMN or N-min) in a laboratory, but some simple test methods are also available for field use (test strip, Reflecto-quant, etc.). To estimate the mineralizable and therefore the N available mid-term, many different methods have been developed, amongst them the organic nitrogen (N org) fraction of electro-ultrafiltration (EUF) and anaerobic mineralization. This review will provide an overview on sampling and storage techniques, including available analytical methods for nitrogen determination, as well as their advantages and restrictions and possible causes of failure, in order to identify gaps in our knowledge and further research needs.