Soils for Vegetable Gardening
Vegetable plants grow
best in a fertile, well-drained soil of loamy texture. Sandy loam soils, well-supplied with organic matter, are easily worked
and are quite productive. Unfortunately, many gardens do not contain such soils.
Very coarse, sandy soils
dry out rapidly and are difficult to maintain at a high level of fertility. Clay soils are hard to work and usually remain
wet until late in the spring. These soils are often yellow or dark brown and sticky when wet; or grayish in color where drainage
is poor. Clay soils tend to form a hard crust after a heavy rain and become so compacted that the plant's root system is deprived
of essential oxygen required for growth. Clay and sandy soils must be modified for successful vegetable gardening.
To obtain a desirable
soil for gardening, consider the following areas of concern: water drainage, moisture condition at the time of working, erosion,
texture and structure, fertility, and pH (acidity or alkalinity).
production cannot be expected on poorly-drained soils. Where drainage problems exist, and where an outlet is available, four-inch
drain tile in lines 25 feet apart is suggested. The tile should be at least 2 feet deep. The fall in the lines will depend
on the outlet and length of lines, but water needs a fall of at least 2 inches per 100 feet of line.
In many home gardens,
improving subsurface drainage with tile lines is not practical. Therefore, surface drainage is very important. The surface
should be graded so that excess water will be removed promptly, but in a controlled manner, to prevent erosion. Leveling will
eliminate pockets and low spots where water tends to stand for long periods. Adding organic matter to clay and clay-loam soils
will also improve drainage and aeration.
Another option for dealing
with poor drainage, is to grow the vegetables in raised beds or on planting ridges. However, keep in mind that proper water
management during periods of drought may be more difficult in raised beds. See Home, Yard and Garden fact sheet 1641-92 for
more details on raised-bed gardening.
Conditions at Time of Working
Many anxious gardeners
work the soil in early spring when it is still too wet. The soil should not be tilled or spaded until it is sufficiently dry
to crumble when worked. Experienced gardeners often use the "squeeze" test to determine if the soil is ready. With a spade,
turn over a slice of soil about 6 inches deep. Pick up a handful of soil and squeeze it. If the soil remains in a tight ball
when pressure is released, wait several days (without rainfall) before spading or tilling. If the soil crumbles when pressure
is released, it is ready for working. Soils high in clay content are easily damaged if worked when wet.
Some clay soils benefit
from fall tilling or spading. Such soils will be loose and fluffy in the spring as a result of the conditioning effect of
freezing and thawing that takes place in the winter. Fall-worked soils often require only leveling and a light raking in the
spring before planting. Be cautioned, however, that such fall-worked soils can be compacted quite easily if worked too wet.
Soil texture and structure
can be modified by using soil conditioners. Soil conditioners act to improve soil aeration, drainage, moisture-holding capacity
and tilth, or workability, of the soil. Commonly used soil conditioners include compost, peat moss, sawdust, wood chips, composted
animal manures, green manure crops, coarse sand, and perlite. By incorporating coarse, rather than fine sand, and organic
matter into a garden soil, the gardener can, over time, produce a desirable loamy-type soil. The addition of fine sand to
some soils, especially clay, however, will be detrimental to the soil structure.
A common mistake made
when attempting to improve garden soil is failing to use enough soil conditioning materials. For chiefly clay or sandy soil,
large amounts of conditioners must be used to effectively improve texture and structure.
Condition the soil by
applying 3 to 4 inches of organic matter and, if available, 1 to 2 inches of coarse sand uniformly over the surface of the
garden. Till or spade the material thoroughly into the top 8 to 10 inches of soil.
Temporary Nitrogen Deficiency
Organic materials such
as straw, fresh sawdust, wood chips, and shredded bark require the addition of nitrogen fertilizer when they are incorporated
into the soil. The nitrogen provides extra nutrition for microbes decomposing the added organic matter, preventing a temporary
nitrogen deficiency in the vegetable plants.
Apply 1/4 lb. of ammonium
nitrate or ammonium sulfate for each bushel of mulch material; or 2 lbs. per 100 sq. ft. of a complete fertilizer, such as
5-10-5, 8-8-8, 12-12-12 or similar analysis. If there is any yellowing of the lower foliage and garden plants lack vigor during
early summer, apply additional nitrogen fertilizer.
of Cover Crops
Garden soils benefit
by being protected by a winter crop such as rye or ryegrass (or winter barley in southern Ohio). Rye is preferable for late
(after September 15) cover crops seedings.
Cereal rye and barley
are seeded at a rate of 1/3 lb. per 100 sq. ft. of garden area. Ryegrass is a suitable soil cover crop, but should be seeded
before September 15 for best results. It is seeded at a rate of 3 oz. per 100 sq. ft. or 1 and 1/2 to 2 lbs. per 1,000 sq.
Cover crops prevent
soil erosion and add organic matter when turned under in the spring. However, such crops should be turned over before growth
is so tall they are difficult to handle. Cover crops may be seeded between garden rows in August through September, even if
vegetables are not yet harvested.
A soil test should be
made to determine if limestone is needed to adjust the pH of the soil. Most vegetables grow best under slightly acid conditions
with a pH of 6.0 to 6.8. Contact your local Cooperative Extension office for information on getting your soil pH tested.
The authors gratefully
acknowledge James D. Utzinger and William M. Brooks for their 1983 fact sheet on which this is based.
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Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
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