Sunday, September 20, 2009

Vegetable Gardening: Soil Preparation

Harwich resident Anne Stewart's winning "large garden" is brimming with squash, corn, beans, peppers and tomatoes. Two triangles filled with zinnias, sunflowers and alyssum form the entry to the garden. For Stewart, successful vegetable gardening means more than just popping a few seeds in the ground. She likes to take gardening back to the basics. "Soil preparation is everything. If you prepare the soil with organic composts and manure, you can 'coast' during the growing season." Stewart also notes that gardening "means solace, peace and quiet, and the continuance of the generations." Photo by Paul Blackmore, Cape Cod Times. h/t: theediblegarden.

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Regardless of the soil in your garden, it can be improved by adding organic matter. If your soil is heavy clay, the addition of organic matter improves both drainage and aeration and also allows better root development. Liberal amounts of organic matter help sandy soil hold water and nutrients.

Where do you get organic matter?

This magical stuff which improves soil and serves as a food source for soil fungi and bacteria comes in the form of peat moss, compost, hay, grass clippings, barnyard fertilizer, shredded bark, leaves or even shredded newspapers.

When adding organic matter to soil, supply enough to physically change the soil structure. Ideally, at least one-third of the final soil mix should be some type of organic material. To accomplish this, spread a 2 to 4 inch layer of organic material over the garden surface and till it to a depth of at least 6 to 10 inches. Apply the recommended rate of fertilizer over the garden surface at the same time, and till it in along with the organic material. -- Organic Lifestyles

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Here's a nifty tip (particularly for gardeners using the raised bed method, employing untreated wood or cinder blocks): To smother existing grass and weed roots, prepare your empty beds by spreading a layer of newspaper about 12 sheets thick. -- Flower Gardening Made Easy

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This is a chart to help you find the right sweet soil pH level for your healthy raised vegetable garden. -- Raised Vegetable Garden

Vegetables Ideal pH
Artichoke 6.5 – 7.5
Asparagus 6.0 – 8.0
Beans 6.1 – 7.5
Beet Root 6.0 – 7.5
Broccoli 6.0 – 7.0
Brussel Sprouts 6.0 – 7.5
Cabbage 6.0 – 7.5
Carrot 5.5 – 7.0
Cauliflower 5.5 – 7.5
Celery 6.0 – 7.0
Chicory 5.0 – 6.5
Corn 5.5 – 7.0
Cress 6.0 – 7.0
Cucumber 5.5 – 7.5
Garlic 5.5 – 7.5
Horseradish 6.0 – 7.0
Kale 6.0 – 7.5
Kohlrabi 6.0 – 7.5
Leek 6.0 – 8.0
Lentil 5.5 – 7.0
Lettuce 6.1 – 7.0
Mushroom 6.5 – 7.5
Mustard 6.0 – 7.5
Onion 6.0 – 7.0
Parsnip 5.5 – 7.5
Pea 6.0 – 7.5
Peanut 5.0 – 6.5
Pepper 5.5 – 7.0
Potato 4.5 – 6.0
Pumpkin 5.5 – 7.5
Radish 6.0 – 7.0
Rhubarb 5.5 – 7.0
Sweet Potato 5.5 – 6.0
Shallot 5.5 – 7.0
Soybean 5.5 – 6.5
Spinach 6.0 – 7.5
Tomato 5.5 – 7.5
Turnip 5.5 – 7.0
Water Cress 5.0 – 8.0
Watermelon 5.5 – 6.5

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Lewis Brady credits his gardening successes this year to using shredded newspaper as mulch. Photo by Sefton Ipock. Gardener says newspaper makes for bigger crops via Knox News.

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Soil pH (acidity) explained and what to do about it

The acidity of a garden soil (referred to as its 'pH') is measured on a scale 0 to 14, with 7 being neutral (i.e. neither alkaline or acid), an alkaline soil has a pH value above 7, a value below 7 indicates an acid soil. In simple terms, the acidity reflects the amount of calcium (i.e. chalk or lime) in the soil, this changes over time partly as it is leached out of the soil by rain etc. and also by growing vegetables, using fertilizers and manures; all this leads to increased acidity as time goes by.

Clay soils hold calcium better than sandy soils where the calcium may be leached out relatively quickly, the natural tendency is for clay soils to be alkaline (pH above 7), while sandy soils tend towards acid (pH below 7).

The importance of the pH is that it affects the release of nutrients and worm/micro-organism activity and, high acidity, increases some plant diseases.

The pH of a garden soil has an affect upon plant growth; generally vegetables like a soil with a pH of around 6.5 (i.e. slightly acid) but there is no common pH preference for shrubs and flowers etc, some don't mind, others desire less acidity while other desire more (some plants are often classed as 'chalk/clay loving or hating', this just reflects the pH preference of the plant).

A vegetable plot is likely to need more attention regarding the soil pH than flowers or shrubs.

The pH of soil can be easily determined by using one of the readily available soil sampling kits; usually the method is to add a chemical to a mixture of the soil and water, the colour change of the sample is then compared to a chart provided and the colour match identifies the pH of the sample. It is recommended that two or three soil samples from different areas are tested to avoid a possible unrepresentative test result.

How to change the acidity (pH) of a soil

To decrease the acidity, add lime - the preferred method is to use ground limestone or chalk. The amount required will depend upon the soil type and the degree of increase in pH desired. Lime should not be added at the same time as fertilizer or organic material (they can react).

If both organic material/fertilizer and lime are required, add the organic material/fertilizer first (in Autumn) and the lime in February/March. If just liming is required, it should be applied to chalk/clay soil in Autumn or to sandy soils in Spring.

Lime is traditionally spread on the surface of the soil for rain to wash it in but on medium to heavy soils, it is better to dig it in to the top spit of soil.

The amount of liming necessary will depend upon the type of soil, the actual pH and the desired pH; the wider the gap (for a given soil type), the more liming required. As a very rough guide, to take a soil to 6.5 pH the suggested liming (using ground limestone) is:

Lime should not be required each year, with vegetable crop rotation every three or four years should be adequate.

To decrease the acidity, add compost or other organic material. -- Gardening Data

There are many expensive PH meters available however, a simple one like this is all you need to ensure optimal growing conditions for your vegetables, flowers and lawn:


  1. Ph is very important. Good tips in this post.

    Also for squash the pH should be 6.0-7.5.

  2. so this is what it's about - selling your ph meter! what a waste of time reading this article!

  3. Impressive Anne congratulations ! what a good gardener you are , thanks for sharing your information about your garden im very envy i hope that i have like your garden.

    i have some garden accessories which i visit some sites about garden spinner and they were very beautiful and colorful . think this will help your garden to add life

  4. Wow, got your page from my twitter friend. Nice info, thank you

  5. Vegetable gardens are fun, and with a little prep, very easy. Even if you have never planted a vegetable garden before, you can get started right away, and be very successful.