Soil
PH...An Important "Key" To Successful Gardening--In Plain English
By Fred
Davis
Soil ph is among the least understood and most universally ignored or abused "keys" to getting the kind of results that makes one gardener--and his or her gardening results--stand head and shoulders above all others.
Just what is pH anyway? The term "pH" is nothing more than a way of expressing the amount of acidity or alkalinity in the soil. A "sour" soil is acidic to one degree or other, while "sweet" refers to an alkaline soil. Most New England garden soils are, by nature, moderately to strongly acidic and must often be "adjusted" to encourage them to grow better crops and flowers. Deep woods and blueberry barrens are usually very strongly acidic...that's how the plants which grow there like it.
The pH scale ranges from 0 to 14 (7 being neutral--neither acidic nor alkaline). Numbers smaller than 7 indicate acidic conditions and, as you might readily guess, those above 7 indicate alkaline conditions. Most vegetables, herbaceous perennials, annuals, field crops and fruits grow, produce, and look their best at a pH of between 6.5 and 7.0--slightly-acidic-to-neutral. Soils which are too acidic or too alkaline for the crop need to be adjusted to very nearly the ideal pH. Ground limestone or wood ashes raises the pH to sweeten acidy soil, while adding carefully-measured amounts of sulfur increases acidity, lowering the pH.
How important is correct pH? It is important to understand that nutrients--substances which plants use for food--are much more readily available for plants to use when soil pH is as it should be. For example, a soil may have ample nutritional elements (fertilizer) but if it is very strongly acidic or far too alkaline, those nutrients are quite simply locked-up and almost completely unavailable. Adjusting soil pH to the recommended level releases food for the plants to use.
Here's something you've probably never heard before: large quantities of the three primary nutrients--nitrogen (N), phosphorus (P) and potash (K)--are blocked by a soil pH more acidic than about 5.0. Phosphorus, in particular, is bound-up and almost totally inaccessible at pH levels below about 6.2 or 6.3 (moderately acidic). You can almost literally pour phosphorus into the garden all you want or can afford...but if the soil is even a little too acidic, the plants simply can't get at it. Soils containing ample organic matter (compost, rotted manure, etc.) fare better but every good gardener strives to maintain correct pH. Odd as it may sound, a great many frustrating problems in the field or garden could be solved by a simple soil test and then adjusting soil nutritional condition--especially pH--appropriately.
The logical and responsible next step? Drop by your local Cooperative Extension
Service office and pick up a soil sample kit. It's some of the best
insurance you can obtain against disappointment in the garden!
For preferred pH levels of a great many ornamentals and vegetables, see “Appendix 1” of Fred’s book, “Keys To The Garden Gate,” at: http://www.hillgardens.com/libragardinale_tr26057.htm#appendix. While you’re there, download your free copy of the book.
Fred Davis is a Master Gardener, Master Composter, lecturer, and
long-time nurseryman. He and his wife, Linda, own and operate a
popular perennial nursery in Palermo, Maine, and maintain a no-frills
gardening information website at: http://www.HillGardens.com/
