Estimation of available n status of soil by wheat and barley: A-values

The authors have examined the effect of nitrogen form, rate of addition and the timing of the nitrogen fertilizer application on the A-value. Two non N sub(2)-fixing crops were used to demonstrate the influence of these factors and provide information on the assumptions inherent with the use of A-value methodology to measure biological N sub(2) fixation. super(15)N labelled fertilizer was employed as the technique to determine the uptake of inorganic N in the soil and the uptake efficiency of fertilizer N.