|
back
| home
University
of Rhode Island GreenShare Factsheets
Improving
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.
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 the
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).
Satisfactory vegetable 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.
Growing vegetables in raised beds or on planting
ridges is another option for controlling drainage. However,
keep in mind that proper water management during periods
of drought may be more difficult in raised beds.
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
Use the "squeeze" test to determine if the soil is ready:
use a spade to turn over a slice of soil about 6 inches deep,
then 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 winter freezing and thawing.
Fall-worked soils often require only leveling and a light
raking in the spring before planting. Fall-worked soils can
be compacted quite easily, however, if worked when 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 sand and organic matter into a garden
soil, the gardener can, over time, produce a desirable loamy-type
soil. The addition of fine sand, however, into some soils,
especially clay, will be detrimental to the soil structure.
A common mistake made when attempting to improve
garden soil is failing to use enough soil conditioning material.
For soil which is mostly clay or sand, 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.
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.
Garden soils benefit by being protected by a winter
crop such as winter rye. Winter rye is preferable for late
(after September 15) cover crops seedings and is seeded at
a rate of 1/3 lb. per 100 sq. ft. of garden area.
Cover crops prevent soil erosion and add organic
matter when turned under in the spring. Cover crops should
be turned over before growth is so tall they are difficult
to handle. Cover crops may be seeded in August or September
between garden rows before vegetables are 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.
See GreenShare Factsheet on soil
testing for more information.
Adapted from Marianne
Riofrio and E.C. Wittmeyer, Ohio State University Extension,
2000
Pesticides
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
For more
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
University
of Rhode Island Cooperative Extension provides equal program
opportunities.
|