How large of an area does one kit cover?

One SoilKit can be used to test 10,000 square feet using a composite soil sample. Larger areas may require more than one test kit. Additionally, seperate test kits should be used for areas with different managment history (e.g. fertilizer or lime applications) or different soil types, even if they are less than 10,000 square feet. This way, you can get customized recommendations specific to each part of the lawn or garden based on the results from  seperate tests. In general, problem areas should be tested separately from healthy areas.