Soil bulk density
The bulk density of each individual sample will be determined as the oven-dry mass of soil divided by the aluminum ring volume. Then, for each field, an average bulk density of the soil surface will be determined for the entire field using the collected 20 calibration samples. The average bulk density will be multiplied by the gravimetric moisture content of each individual sample to calculate the volumetric moisture content of each core sample, for comparison with the POGO measurements.