- Collection of articles from Oregon State University on various aspects of soil: use of amendments and cover crops, temperature, acidity, moisture, and testing.
- Oregon horticulturalist offers information on soil components, pH, testing methods, and nutrients, and means of improving it by using amendments and improving drainage and aeration.
- Ohio State University fact sheet covers the benefits of testing garden soil and provides recommendations for testing frequency, collecting a sample, and submitting to a testing lab.