Soil Sampling with a Modified Chainsaw

In uncultivated fields containing residual banded fertilizer, wide variability in analytical results for individual soil samples can make it extremely time‐consuming to obtain a representative composite for analysis. This study was done to test whether individual soil samples, taken from a series of slots cut across bands of residual fertilizer, would show less analytical variability than samples taken at a series of random points. A chainsaw fitted with a catcher was used to collect soil from slots cut across stubble rows, and an auger used to take point samples, on field plots with residual N, P, K, and S fertilizer banded ≈ 6 cm deep at 18‐cm spacing. Plots at eight sites on Typic Cryoborolls, mostly clay loam in texture, were sampled after harvest. The samples were analyzed for extractable N, P, K, and S. Out of 32 comparisons, coefficients of variation (CV) in analytical results were lower in 28 instances when samples were taken by chainsaw rather than by auger. Judging from CV values, a composite sample made up of soil from ≈ 15 slots would in most cases have given an accurate estimate of residual amounts of all four crop nutrients at the eight sites. With an auger, from 40 to 50 sampling points would have been required for comparable accuracy. The results suggest that, when sampling uncultivated soil containing residual banded fertilizer, a valid composite sample could be obtained more conveniently by slot‐cutting than by sampling at points.