This study was conducted in field C, on individual Schizachyrium scoparium plants which were of equal size.
PVC tubes (15.2cm diameter and 15cm height) were driven into the soil around Schizachyrium scoparium plants. Initial NO3 and NH4 levels at each experimental unit were determined before assigning treatments to the tubes. Four treatments are being studied: NO3 and NH4 isotopes and two controls. The initial NH4 pool was increased 5% using the NH4 isotope. The initial NO3 was very low (1/10 th ppm ), so enough NO3 isotope was added to bring the total KNO3 level to 1 ppm.