Before taking soil samples or checking roots for galls, divide the field into areas that reflect any differences in cropping history or soil type. For soil sampling, subdivide these areas into blocks of about 10 acres (4 ha). If there are areas where there has been poor growth, treat them as separate blocks, even if they are much smaller than other blocks. Assign each block a number and collect soil from a series of points in each one, following a random pattern as shown in block no. 10.

Adapted from: 1996. Integrated Pest Management for Cotton in the Western Region of the United States, Second Edition. Oakland: Univ. Calif. Div. Agric. Nat. Res. Publ. 3305.