Nitrate and phosphate values of soils in relation to soil sampling methods

In order to get nitrate and phosphate values of soils, investigations were conducted to test the suitability of different soil sampling methods. Including two one-piece borer types eight different soil sampling methods (hand/hammer, Dutzi, N-caterpillar, Geonor) were examined in relation to control samples, drawn manually by a three-piece borer. Soil samples (0-90 cm) were drawn from two fields with different soil characteristics at two different dates. In all cases hand/hammer-methods resulted in a remarkable overestimation of the nitrate and the phosphate concentration in soil samples. Sampling methods, which realize a combination of high blow frequency and low energy input per blow allow values not significantly different form control levels. Even those systems are not able to eliminate critical effects of physical soil traits. The effects of different borer types were of minor importance.