Fall is the best time of year to test your garden soil, and the main reason is time. The amendments that fix pH work slowly, so a test this fall gives lime the months it needs to do its job before you plant next spring. But there's a twist most gardeners don't expect. When soil labs look at home garden samples, a huge share of them come back with too much phosphorus and potassium already, often from years of adding fertilizer, manure, and yes, compost.
In this episode I walk you through why fall testing works so well, how to take a sample that tells you the truth, and whether a home test kit is good enough. Then we'll go line by line through a soil test report so you know what pH, buffer pH, phosphorus, potassium, and organic matter are telling you. And then we'll talk about what to add this fall, and what to skip, including lime, sulfur, wood ash, manure, gypsum, and coffee grounds, with adjustments for cold, moderate, and mild-winter climates.
Let's dig in!
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- Penn State Extension (White) — Fall Is the Perfect Time for Soil Sampling: https://extension.psu.edu/fall-is-the-perfect-time-for-soil-sampling
- University of Missouri IPM, Missouri Environment & Garden (Nathan) — Don't Guess — Test Your Soil: https://ipm.missouri.edu/MEG/2014/4/Do-Not-Guess-Test-Your-Soil/
- Faber, B. A., Downer, A. J., Holstege, D., & Mochizuki, M. J. (2007). Accuracy varies for commercially available soil test kits analyzing nitrate–nitrogen, phosphorus, potassium, and pH. HortTechnology 17(3): 358–362: https://oc4h.ucanr.edu/sites/default/files/2010-07/35923.pdf
- University of Kentucky Cooperative Extension (Lee) — No P on my Lawn!: https://kers.ca.uky.edu/core/reports/Story/s/3900/2026
- University of Missouri Extension (Geist, quoting Trinklein) — Ashes to ashes: https://extension.missouri.edu/news/ashes-to-ashes
- Iowa State University Extension and Outreach (Fillius, Rindels, & Steil) — Using Manure in the Home Garden: https://yardandgarden.extension.iastate.edu/how-to/using-manure-home-garden
- Oregon State University Extension (Pokorny, with Brewer) — Coffee grounds boost soil health — and help control slugs: https://extension.oregonstate.edu/news/coffee-grounds-boost-soil-health-help-control-slugs
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