Estimation of potentially mineralisable nitrogen in soil by KCl extraction. II: Comparison with soil N uptake in the field

The potentially mineralisable nitrogen extracted from 10 soils by two methods involving boiling with dilute KCl were compared with the actual uptake of soil N by spring barley in the field, as determined with the use of 15 N-labelled fertiliser. Generally good correlations were found for those soils which had previously been cropped with cereals (defined in Great Britain as either «N-Index zero», or «low nitrogen status» soils, for fertiliser recommendations), with the results obtained by the more severe of the two methods being somewhat better than by the other method. When organic matter content was also taken into account, correlations were improved [...]