Earthworms engineer the soil environment, help with carbon cycling, improve water infiltration and plant productivity, and are an important food source for native birds. They are also a biological indicator of soil health.  The best time to count earthworm populations is early in the spring, or after the soil has wetted up in the autumn. Counting earthworms when it is warm and after rain often provides the best population estimates. Avoid taking samples when the soil is very dry. Soil should have been wet for a few days prior to sampling. When assessing earthworm numbers, it is important to take more than one sample from within each field; 10 samples per field is ideal. Comparisons between cultivated parts of the field and margins can be useful.   Visit this page on the AHDB website for instructions on how to count your earthworms.