Once you have made an assessment of the climatic conditions your fruit trees and bushes may encounter in your location, another vital factor to consider is the soil. Several characteristics of your soil will have an influence on the productive capacity of your fruit garden. They include soil type or texture and pH:
First, a good look at your soil texture is in order. If your planting area is flat and small, say a few hundred square feet, very likely your soil type and texture will be fairly uniform throughout. If, however, your area possesses some obvious changes in elevation or covers several acres, you may encounter several different soil types. Each one may be suitable to growing different things. The major soil textures can be generally defined as:
Sand, as most of us know it, is made up of fairly large particles, relatively speaking. These are weathered pieces of minerals and still fairly coarse in texture. Large pore spaces for water and oxygen are found between sand particles. Relatively little organic matter is present in a very sandy soil. Water tends to run through sand quite quickly. One place to watch out for sand is right around the foundation of your house. The sand builders use as backfill to provide good foundation drainage is particularly lacking in plant nutrients.
Loam soils are composed of medium size particles. They are a combination of about 50% weathered sand and up to 25% clay. Silt (very fine particles) make up the remaining soil particle percentage. The overall texture is finer than sand. The soil holds together as a more cohesive mass and has a substantially greater capacity to hold water and nutrients than pure sand does. These soils are commonly found where there has been ongoing decay of plant matter through natural processes. Well aged compost commonly has a loam-like texture.
Clay soils are made up of very small, fine textured, highly weathered particles. Clay tends to have very high moisture holding capacity which can sometimes become a problem by water– logging root areas. Clay particles have strong ionic charges and are chemically attracted to each other. As a result clay soil has a tendency to become very hard, almost like cement, if allowed to dry out completely. This happens because its very small particles fit so closely together.
Note that at this point the terms soil type and texture have been used in their broad general sense, as interchangeable terms. In the technical word of soil science the term “soil type” actually has a very specific meaning. There are many soil types, each unique, named, and denoting a specific percentage makeup of sand, loam, and clay. For purposes of a small garden it may be interesting, but not critical, to know your specific soil type by name.
Ideally, a desirable fruit garden soil will be composed of 50% particles and 50% pore space — the pore spaces containing a balance of half water and half air under the best growing conditions. The particle fraction typically includes up to 5% organic matter, that is decaying vegetation or animal matter — often manure. The remaining 45% of the particle fraction is made up of combinations of sand, loam, or clay particles as discussed above.
In between the three main soil types are “combination soils” — the sandy loams and the clay loams. As their names imply, they are a mixture of a varying percentage of sand and loam or loam and clay. These are often the best soils for fruit growing as they normally have a better balance of desirable characteristics. For example, a sandy loam may have good soil drainage, thanks to the sand portion. Yet it will also have a higher available mineral content and good ability to hold moisture due to the organic component of the loam. Conversely, clay loams may have high water holding capacity, but do not cement as badly when dry because air space is present between the larger particles that make up the loam portion. All other factors being equal, a sandy loam will be the most versatile for growing a selection of different fruit. You can perform a quick, handy “dirty thumbs” test right in the garden as a way to estimate your soil type. For a more precise measure the “jar sedimentation test” and soil triangle can be used.
Here it is — soil pH. Every gardening book talks about it, but most readers are still confused by soil pH. It always sounds like chemistry and quite frankly, it is. For the home gardener, it is also not essential to understand all the chemistry involved with pH measurement. To keep the explanation simple, we will stick to the basic ideas you need to understand in growing your fruit.
The term “pH” is actually an abbreviation for the phrase “potential hydrogen.” It is a measure of the amount of available hydrogen ions in a sample of soil. This measure is used to indicate the acidity or alkalinity (sometimes casually referred to as sweetness) of the soil. Knowing the acidity or alkalinity of a soil can be important because it affects the amount and form of nutrients available to the plant.
A scale of 0 to 14 is used to express soil pH. To be suitable for fruit, it has been generally accepted that a soil should have a pH of 6.0 to 7.0; with 6.5 to 6.8 preferred (although at least one fruit crop, the blueberry, prefers a pH of 4.5 to 5.5.)
Most garden centers sell small home pH measurement kits, that although not extremely accurate, can give you a “ball park” pH reading. Another resource for soil testing is your local cooperative extension service which can, for a small fee, send your soil sample to a university lab for testing. It is a good idea to take a complete soil sample before starting your fruit garden (or other permanent planting for that matter,) so that you know what you are working with when you start. It will be unlikely that you will need to repeat this test very often, assuming that your initial pH is in an acceptable range and you don’t encounter nutrition related problems with the growth of your garden.
For an in-depth look at building a productive soil read Building Soils Naturally.
©2013. Adapted from the Backyard Orchardist: A complete guide to growing fruit trees in the home garden by Stella Otto.