Agricultural soils can be sampled by removing subsamples from uniform land areas to a depth of
15 to 20 cm. Uniform areas generally have similar soils and slopes, and do not include washed-out
areas, bottomlands, or other dissimilar areas. Soil subsamples should be placed in a plastic container
to avoid contamination and mixed together thoroughly. Generally, 25 to 50 subsamples per hectare
are sufficient to obtain a representation of the soil.