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Series of projects, articles, and tips on fertilizing, composting, and nutrient management.

Collection of articles from Oregon State University on various aspects of soil: use of amendments and cover crops, temperature, acidity, moisture, and testing.

Covers a wide range of garden soil topics, including soil types, pH, nutrients, testing, composting and fertilizers.

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.

Collection of articles and resources about the horticultural uses of perlite and vermiculite.

One-page site giving suggestions on where to purchase vermiculite in the United States, along with some uses and properties of vermiculite.