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Climate and Drainage

From "Fresh from the Garden"
episode DFFG-101

Knowing your climate and site will help you make important decisions about your vegetable garden, including how to lay out the beds and rows. It's important to select a site where air is able to flow freely, since good air circulation is a must for growing healthy vegetables. Even moderate air circulation reduces the chance of disease: breezes help dry the plants.

If you live in an area where strong winds prevail, however, you'll need to protect your crops from their potentially damaging force. It's sometimes difficult to know if winds will be a problem, but here are some clues:

If your garden has a beautiful long-range view, it may also be windy.
Other windy sites include those on coastal areas, as well as those on western or northern exposures, especially when weather fronts or storms pass through.
In windy sites, place the garden where there is already a wind barrier, or plan on creating one with bushes or shrubs.

Figure A

Figure B

Figure C

Figure D

Figure E

Soil temperature is just as critical to plant growth as air temperature. Use a soil thermometer (figure A) to determine where the soil will slow down some plants' growth. The soil thermometer will allow you to check soil temperatures in several different locations quickly. You can purchase a standard soil thermometer at your local hardware store or gardening center.
To test soil temperature, push the probe 4 to 6 inches into the soil; the temperatures will display on the gauge. You'll need a soil temperature of about 40 to 45 degrees Fahrenheit -- the composition of the soil responsible for supplying food for the plants doesn't really become active until it reaches that number.
Another important consideration when selecting a site for your garden is ensuring that the plants are properly fed. Pick a site that isn't prone to flooding or standing water. The site should be level or slightly sloping. Try to avoid locating your garden in a low spot where water and cold air tend to collect. To determine whether how well your site will drain, you'll need to perform the "percolation test" using a spade, a water hose and a stopwatch.
Using the spade (figure B), dig several 1-foot holes where you want to locate your planting beds. Next, fill the holes with water from a garden hose. After the water has drained from the holes, add a wood stake (figure C) to help track the rate of drainage and refill the holes with water (figure D).
Use a stopwatch to time how long it takes for the holes to empty (figure E). Well-drained garden soil should drop 1 to 2 inches per hour. Soil that drains close to these rates will readily support the growth of healthy vegetables.
Drainage rates that are slower indicate that the soil is too heavy with clay or other organic materials like rock beneath the planting bed that might cause the slow drainage. If the soil drains much more quickly, it is probably porous and contains too much sand. Drainages rates faster than 1 to 2 inches in 15 minutes or less also require correction. To remedy either of these drainage problems, simply incorporate 2 to 4 inches of organic compost into the top of the soil.
Most vegetable plants need about 1 inch of water per week. The type of soil in your garden, however, will determine how much additional water may be needed. The ideal gardening soil is soft, loose and crumbly. Most soils are a mixture of sand, slit, and clay. Soil differs widely throughout the country in their content of plant nutrients; the perfect soil should be about 45 percent mineral, 5 percent organic matter, 25 percent air, and 25 percent water.