RAPID PROCEDURES FOR PREPARING SOIL AND KCL EXTRACTS FOR N-15 ANALYSIS

An apparatus for grinding plant and soil samples to < 250um for N-14 analysis is described. This inexpensive and easily constructed roller grinder uses bottles for grinding individual samples, thus eliminating the potential for cross contamination. The unit running over-night is capable of grinding 70 samples. In addition a method is described for diffusing NH4+ and NO3 onto filter paper for subsequent N-15 analysis. This method utilizes disposable test tubes and an incubator-shaker to help speed the diffusion process. At low A% N-15 (2-3%) a diffusion period of 7 days is sufficient for total N-15 recovery. At an A% N-15 of 8% the diffusion period needed to be extended to 10 days for total recovery.