Any observable variation in previous crop growth, soil texture, moisture and draining patterns, or cropping history will constitute a subdivision. An effective sampling map may then be constructed. The sampling pattern is based on the sampling map and should be designed to obtain a reliable representative sample with as little sampling error as possible. An example of a recommended soil sampling pattern for fallow ground or an established crop is shown in Figure 1. Number, size, and cost of samples Sample size depends on the area and crop being sampled, the crop's value and any supplementary information to be gathered during sampling.
Sample size is measured in terms of the number of cores of soil constituting the sample.
The precision of the resulting nematode estimates can be improved by increasing the number of soil cores in the sample. This is also less expensive than increasing the actual number of samples. A good approach in sampling is to bulk soil cores in a clean bucket, mix thoroughly, and submit one quart of the mixture for processing. One sample may be used to represent up to five acres of a uniform field subdivision as determined by mapping. Each sample should contain at least 20 individual cores, or if representing less than five acres, at least four cores per acre.