TECHNICAL PAPER #8
UNDERSTANDING SOIL PREPARATION
By
Paul J. Abrahams
Technical Reviewers
Dr. J.W. Fitts
Dr. Nail Ozerol
Richard Roosenberg
Published By
VITA
1600 Wilson Boulevard, Suite 500
Arlington, Virginia 22209 USA
Tel: 703/276-1800 . Fax: 703/243-1865
Internet: pr-info@vita.org
Understanding Soil Preparation
ISBN:
0-86619-208-5
[C]1984, Volunteers in Technical Assistance
PREFACE
This paper is one of a series published by Volunteers in
Technical
Assistance to provide an introduction to specific
state-of-the-art
technologies of interest to people in developing countries.
The papers are intended to be used as guidelines to help
people choose technologies that are suitable to their
situations.
They are not intended to provide construction or
implementation
details. People are
urged to contact VITA or a similar organization
for further information and technical assistance if they
find that a particular technology seems to meet their needs.
The papers in the series were written, reviewed, and
illustrated
almost entirely by VITA Volunteer technical experts on a
purely
voluntary basis.
Some 500 volunteers were involved in the production
of the first 100 titles issued, contributing approximately
5,000 hours of their time.
VITA staff included Leslie Gottschalk
and Maria Giannuzzi as editors, Julie Berman handling
typesetting
and layout, and Margaret Crouch as project manager.
VITA Volunteer Paul J. Abrahams, the author of this paper,
is a
chemist for the McElrath Poultry Company and also a
full-time
farmer who raises corn, clover, and sheep.
VITA Volunteer reviewers
Dr. J.W. Fitts, Dr. Nail Ozerol, and Richard Roosenberg are
also experts in the field of soil preparation.
Dr. J.W. Fitts is
an agronomist with Agro Services International, Inc., an
agricultural
consulting firm. He
was the head of the Soil Department at
North Carolina State University, and Director of the
International
Soil Fertility Evaluation Program at North Carolina State
University for several years.
He has published widely in the
fields of agronomy and soil science.
Dr. Nail Ozerol is the
director of N.H. Ozerol & Associates, a health care and
nutrition
consulting firm. He
has published widely in the fields of
agriculture and nutrition.
Richard Roosenberg is program director
of the Tillers Research Program at The Nature Center, which
reviews animal-powered farm technology for its adaptation to
present needs in the United States and developing countries.
VITA is a private, nonprofit organization that supports people
working on technical problems in developing countries.
VITA offers
information and assistance aimed at helping individuals and
groups to select and implement technologies appropriate to
their
situations. VITA
maintains an international Inquiry Service, a
specialized documentation center, and a computerized roster
of
volunteer technical consultants; manages long-term field
projects;
and publishes a variety of technical manuals and papers.
UNDERSTANDING SOIL PREPARATION
by VITA Volunteer Paul J. Abrahams
I. INTRODUCTION
The purpose of soil preparation is to develop a planting
medium
that will foster the best possible growth of agricultural
crops
while preventing the deterioration of the land through
erosion,
destruction of soil structure, or nutrient loss.
The soil
preparation system used must be economical, since a large
part of
the expense in raising a crop occurs before the seed is ever
placed in the ground.
OBJECTIVES OF SOIL PREPARATION
The immediate goals to be accomplished in soil preparation
are:
*
destruction of weeds,
*
incorporation of organic material,
*
incorporation of fertilizers and lime, and
*
development of the proper seed bed.
Destruction of Weeds
Weeds compete with agricultural crops for moisture,
nutrients,
and sunlight. They
also hinder harvesting, particularly if they
are viney types.
Some weeds are poisonous to people and animals.
Proper soil preparation coupled with effective crop rotation
will prevent the emergence of weeds at the time of planting.
This allows crops at their most tender stage to grow without
competition. Careful
soil preparation will also retard the growth
of weeds as the crops develop, making cultivation and
harvesting
easier.
Incorporation of Organic Material
Organic matter has many beneficial qualities that aid plant
growth:
(1)
the ability to retain water for the use of
crops during
drought;
(2)
the improvement of soil tilth (structure);
and
(3)
the ability to hold nutrients in the soil
instead of
being
leached out by rain.
The natural coverings of soil are forests or grasses, which
yearly add organic matter to the soil as dead wood, leaves,
and
roots. Whenever soil
is made bare by the removal of its
vegetative cover the level of organic matter will be
reduced. In
addition, soil microbes, such as bacteria and fungi, and
larger
animals, such as insects and worms, are constantly consuming
organic material.
When the forest or grassland is destroyed to grow crops, the
natural additions must be replaced by the farmer's efforts.
Organic matter is added by working animal manure, compost,
straw,
or leaves into the soil, or by plowing under green manure
crops
such as clovers, vetch, or rye.
Crop residues such as stalks,
vines, and leaves will add to the organic matter level.
Incorporation of Commercial Fertilizers and Lime
Unless green manure crops are used or large amounts of
animal
manure can be added to the soil, commercial fertilizers must
be
used to maintain proper soil fertility.
As a general rule, one
must add plant nutrients in an amount equal to that removed
in
harvested crops.
(See Table 1.) If this is not done, the fertility
of the soil will drop slowly, causing a decrease in
subsequent
yields. Phosphorus
and potassium may not have to be replaced
at the same rate as nitrogen.
Soil tests to determine the
needed amounts of these nutrients can save on fertilizer
expenses.
It would take the addition of approximately five tons of
cattle
manure per acre to replace the nutrients removed from the
soil by
the harvesting of 100 bushels of corn.
A 50-bushel wheat crop
would require four tons.
That is equivalent to the addition of
11,000 kg per hectare of manure on corn and 9,000 kg per
hectare
of manure on wheat.
It would be preferable if all nutrients could be added as
manure
because this would greatly increase the organic matter
content of
the soil. However,
the large amounts of manure needed may be
difficult to obtain.
In general, it may be more efficient to
manure the garden or speciality crops and use commercial
fertilizers on field crops.
Proper soil fertility helps prevent erosion.
Fertile land produces
more and bigger plants in a given area than nutrient-poor
Table 1.
Fertilizer Amounts Needed to Replace
Nutrients
Removed
by Harvesting Corn Grain and Wheat
Grain at
Good Yields
Amount of Fertilizer
Nitrogen Phosphorus
Potassium
Pentoxide
Oxide
(N)
([P.sub.2][O.sub.5])
([K.sub.2]O)
Corn
At 100 bushels per
acre 80 lb
35 lb
21 lb
At 6200 kilograms
per
hectare
90 kg
39 kg
24 kg
Wheat
At 50 bushels per
acre 70 lb
26 lb
13 lb
At 3400 kilograms
per
hectare
79 kg
29 kg
15 kg
land. Growing crops
protect the soil against beating rains.
Crop residues incorporated into the soil increase the level
of
organic material.
Lime must be added to most soils periodically to neutralize
the
acidifying effect of commercial fertilizers.
Even land that does
not need fertilizer usually requires lime because growing
plant
roots cause the soil to become more acid.
If possible, a soil
testing laboratory should be consulted to determine the need
for
soil additives.
Development of the Proper Seed Bed
The development of a suitable seed bed will ensure good seed
germination, allow rapid root growth, and aid in mechanical
cultivation.
The best soil is loose, having a crumb structure that breaks
easily into small pieces approximately three to seven
millimeters
in diameter when handled.
The deeper this crumb condition is
maintained in a soil the better.
Crumb-type soil fits snugly
around the young seed with no air gaps.
This allows the seed to
be bathed in moisture.
Roots will grow readily into this type of
soil. Crumb soil is
easy to cultivate with machinery or by hand.
Tractor or animal-drawn cultivators can gently roll the
crumbs up
to plants, easily killing weeds.
The worst type of soil is one full of hard clods, larger
than
three centimeters in diameter.
The larger the clods the more
difficult the soil is to work.
Seeds covered by clods are surrounded
by air pockets, causing them to dry out too soon.
The
young plant has a hard time breaking through clods and many
will
never get to the surface.
Roots have a similar problem.
Mechanical cultivators will push large clods toward the
young
growing plants, breaking many.
Moreover, clods contain many weed
seeds, which will still germinate if the clod is merely
rolled
around by the cultivator.
Young grass and other weeds will not
be killed unless their roots are broken free from the
surrounding
soil. This cannot be
accomplished by rolling clods (Figure 1).
usp1x4.gif (486x486)
Clods are formed primarily by working (plowing, harrowing,
or
cultivating) soil when it is still wet.
They are particularly
noticeable when a moldboard plow is used on wet ground.
Large
smooth-sided clods are turned up by the shearing action of
the
plow. When these
clods dry out, they are almost impossible to
break down--even with extra harrowing.
The less organic matter a
soil contains, the more likely it is to form clods when
plowed.
Humus in the soil prevents soil particles from cementing
into
clods.
The simplest way to develop a good crumb structure in a
field is
by growing thickly planted legume and grass sod crops in
rotation
with the field crop.
Over time, the roots of legumes and grasses
will crumble even a hard soil to a great depth.
The roots also
open up passages in the soil for the movement of air and
water.
The beneficial effect of these sod crops will last several
years
after they have been turned under.
And livestock can graze on
the growing grasses.
To ensure a good crumb structure as well as a good seed bed:
1.
Rotate sod crops with field crops.
2.
Add as much manure and other organic
material as
possible.
3.
Wait until wet soil is no longer sticky
before working.
Check by
squeezing a handful of soil in your hand.
Soil
that is too
wet will pack together in a sticky lump and
leave your
hand wet. Soil that is dry enough to
plow
will crumble
again easily when pressure is released.
II. SOIL PREPARATION
OF AGRICULTURAL LAND
CATEGORIES OF AGRICULTURAL LAND
Several factors affect the method of soil preparation:
*
length of growing season
*
annual distribution of rainfall
*
soil type
*
slope of the land
*
type of crops to be produced
*
size of farm
*
level of technology
Given the large variation in geographical conditions and
cultural
practices encountered in food-growing, it is easiest to
assign
agricultural lands into three basic categories:
1.
Large-scale agriculture on fertile, level
low-lands
2.
Intermediate-scale agriculture on erodible
uplands of
varying
fertility
3.
Gardens
Much of the world's best crop land is located along the
flood-plains
of major rivers.
Other highly productive areas include
lands that lie on the beds of ancient lakes and oceans,
which
have dried up or moved.
These lands are flat and highly fertile.
In many countries, such areas have been divided into large
grain
and soybean farms that require high levels of technology.
Because these lands are level, erosion is relatively
limited.
The lands are also often wet, discouraging livestock
production.
Even where livestock can be raised in most areas, such land
is
too valuable to be used as pasture; crops bring a better
return
per acre. All these
factors have often led to a mono cropping
system, with fields left fallow, between the yearly
cropping. In
the short run, it is more economical under these conditions
to
add commercial fertilizer than to use green manure
crops. Over
the long term, however, such practices may not be wise, as
they
can wear out the soil, increase erosion, and foster the
growth of
diseases and pests.
The method of farming hilly lands is very different.
In this
case, erosion is the farmer's greatest enemy.
Sloping land
cannot be cropped every year, so it is best to use a system
that
routinely rotates crops with sod pasture.
Soil preparation
machinery must be suited to deal with thick sod.
The garden is a special case for soil preparation because
many
kinds of vegetables with different growing habits are
produced in
a small area of land.
Since the land is worked very frequently,
it is usually not possible to set aside areas for sod
rotation.
Gardens thus need large amounts of organic matter added
yearly to
keep the soil from becoming exhausted.
The size of a garden
should be no larger than one's supply of manure or compost
can
cover.
SOIL PREPARATION OF FERTILE LOWLANDS
This method of soil preparation is used on large level
fields
where erosion is at a minimum.
The main crops are corn, wheat,
rice, millet, sorghum, and soybeans.
Comparative advantages and
disadvantages include the following:
*
Large tractors are used to prepare the
ground for
planting in
the following steps:
-
Commercial fertilizer and lime are spread by
truck
or
tractor-drawn wagon. Fertilizer may be
applied
by
planters.
-
Land is chisel-plowed six to eight inches
deep.
-
Land is then smoothed out by disk harrow or
spike
tooth harrow
after plowing (with very large
tractors,
it is possible to plow and smooth in one
operation
using a large disk harrow).
-
Right before planting, a second smoothing
operation
using disk or spike tooth harrow should
be
undertaken if needed.
-
The seeds of row crops such as corn are
planted on
level
ground if irrigation is not used; on ridges
if
irrigation is used; or on the side of ridges
if land is
salty. Row crops are planted with row
crop
planters. Small grains such as wheat
are
planted
with a grain drill.
*
Labor requirements are low, which is an
advantage when
labor costs
are high.
*
Energy use is very high.
*
Maintenance requirements for machinery are
extremely
high.
*
The cost of the equipment is very high, but
on land
that gives
good yearly yields and where labor costs are
high, this
type of farming will return more per acre
than any
other, particularly if many acres are planted
and machinery
is used to the fullest extent. This
system can
work if one person has many acres of level
land to
cultivate, particularly if crop yields can be
assured
through irrigation. However, this
system will
not work if
existing loan interest rates for machinery
are high or
if grain prices fluctuate widely.
*
If herbicides are used, one or more of the
soil
preparation
steps may be left out. Fields may not
need
to be plowed
or harrowed, for example. No-till
planters can
plant directly in unplowed land by opening
up a furrow
with the disks and spraying the middle to
kill
weeds. However, every few years the
land must be
plowed to
bury excessive crop residues that can clog
planters or
harbor plant diseases.
SOIL PREPARATION ON ERODIBLE UPLAND SOILS
These soils need a sod cover crop for at least half the year
to
keep erosion to a minimum and rebuild soil structure.
The land
on the farm is divided into two, three, or four segments
with one
portion cultivated each year.
Table 2 below shows the relationships
between the slope of a field and the ideal rotation periods
for planting. These
are averages for all soil types. Soils
with
a thin topsoil, particularly when the subsoil is clay,
should be
cultivated less often.
This type of agriculture is highly suited
for small tractors (20 to 40 horsepower) or for animal-drawn
equipment.
Table 2.
Number of Times During a Four-Year Period
That Land May Be Cultivated
Percent Slope(*)
Allowable
Preferred
uspximg.gif (100x600)
0
4
3
0-2
3
2
2-6
2
1
6-10
1
0
Over 10
0
0
(*) Percent slope is
found by measuring the number of feet (or
meters) the land
falls every 100 feet (or meters).
The method of soil preparation is as follows:
*
Apply lime if needed.
*
If the cover crop is thick and viney, turn
land with a
moldboard
plow with a colter. In the second and
subsequent
years of cropping, implements other than the
moldboard
plow may be more efficient and better for the
soil.
These include the chisel plow, depending on
crop
sequence and
weeding techniques.
*
Smooth soil with harrow immediately after
plowing.
*
Wait approximately three to four weeks for
cover crop
to decompose.
*
Smooth with disk or spike tooth harrow with
drag if
needed before
planting.
*
Plant seed with a row crop planter or grain
drill in
rows that run
across the slope of the land. This will
help prevent
the topsoil from being washed away.
Except
where
rainfall is always plentiful during the growing
season, it is
best to plant row crops such as corn in a
furrow two to
four inches (five to ten cm deep). This
will provide
moister soil for germination; make
cultivation
easier (soil can be pushed into furrow to
kill weeds);
and, in the case of heavy downpours, tend
to stop
erosion. In areas of heavy rainfall,
apply
fertilizer at
time of planting.
The amount of labor needed to cultivate a particular area of
sloping land is higher than on the level lowland farm
because
small equipment is used.
However, since the land is only
cultivated a portion of the time, the total amount of labor
needed for the whole farm on the average can be low.
If draft
animals are used, the labor requirement is higher; it takes
longer to cultivate the same amount of land with animals
than
with tractors, and the animals must be fed and housed.
Energy use is moderate since smaller equipment is used.
Moreover, land in the sod part of the rotation will require
little energy use, and if legumes are grown, the nitrogen
fertilizer cost will be lower.
The maintenance requirements of
the machinery used will be proportional to its size.
There will
also be a periodic upkeep required on any fencing used.
The cost of such a system is lower than that for the lowland
farming technique since smaller equipment is used.
However,
because fencing and animals will have to be purchased in the
beginning, initial costs can be high.
Also, a mower might be
necessary if the stock cannot control all the weeds in the
pasture--weed
control during the sod or pasture phase of rotation
becomes very important during the periods when field crops
are
cultivated. In the
long run, the cost per acre of land will be
lower and the animals will provide additional income that is
often steadier than the marketing of grain.
The main advantage of this system is that the sod crop does
most
of the soil preparation itself.
The roots "plow" and "subsoil"
the ground and legumes capture nitrogen from the atmosphere
and
help save on fertilizer expense.
The root action helps
distribute organic matter and nutrients to a great depth in
the
soil, thus fostering the root growth of the cultivated crop
that
follows. While the
field is in a sod crop, erosion will be virtually
halted and when the soil is exposed during the cropping
year it will be less likely to erode because of its higher
organic matter content and water-holding ability.
Contour bands
of sod between row crops will help catch eroding soil on
steep
hillsides.
Many weeds that hinder cultivation in continually cropped
fields
are smothered out during the sod portion of the
rotation. Broad
leaf weeds are hardest hit.
Either the weed seed is killed
before germination or it is consumed by livestock before it
can
reseed.
The only disadvantage to this system is in the time lost in
the
spring during the month-long decomposition period.
Also, plowing-under
a sod crop may be somewhat more difficult than plowing bare
ground.
In general, it is best to use a moldboard plow to turn sod.
However, it may be advantageous on large acreage to use the
no-till
practice for as many years as possible.
With this practice,
a herbicide is used to kill the foliage of the sod.
Seed is then
planted into narrow furrows opened by disks.
Other herbicides
are used to kill subsequent sod and weed growth.
SOIL PREPARATION IN GARDENS
This third category of farming is confined largely to small
areas
of intensively cultivated land where large amounts of
organic
material are added regularly.
The main crops produced are
vegetables. Often,
many different kinds of vegetables are produced
within the garden and many successive plantings and
harvestings take place during the growing season.
The two main methods of soil preparation are clear
cultivation
and mulch gardening.
In deciding which techniques to use, the
gardener should consider the soil structure, the amount of
time
available for tending the garden, and what type of tools and
machinery are available.
A thick layer of mulch:
*
shades out weeds,
*
helps soil retain moisture,
*
prevents erosion,
*
protects soil from traffic compaction,
*
keeps soil from splashing on plants, and
*
reduces the amount of equipment required,
but,
*
on the other hand, may possibly harbor
insect pests and
disease.
Clear cultivation:
*
allows use of mechanical tillage
*
works well against grass-type weeds
*
works well on large-scale cultivating.
In clear cultivation, a small tractor, animal-drawn
cultivator,
power tiller, or hoe is used to keep the areas between the
vegetable rows clear of weeds.
The soil in these areas, which
usually becomes hard due to heavy traffic, is loosened in
the
same process. In
mulch gardening, thick layers of straw, leaves,
bark, plastic film, or newspaper are placed between the rows
to
shade out most weeds.
The soil under the covering remains loose
and retains moisture.
This method makes cultivating machinery
impractical, but requires hand weeding to remove any pest
plants
that may break through the mulch.
Both clear cultivation and mulch gardening require the
addition
of large amounts of manure, compost, and/or fertilizer to
the
soil regularly; use as much manure as possible, up to 10
tons per
acre (2,000 kg per hectare).
The simplest method is to spread
fresh barn manure over the garden at the end of the growing
season and work this into the soil immediately by plowing it
under, mixing it with a tiller, or spading the ground deeply
with
a fork-type tool. By
planting time, the manure will have decomposed
enough so as not to harm the growing crop.
Note that in
tropical areas of relatively high year-round temperature and
long
seasons of very heavy rains, it may be better to spread aged
manure over the garden just before planting.
Organic matter
decays completely very quickly in the tropics, and humus and
nutrients may be washed away by the rains before they can be
of
use to the crop.
If tillage is to be employed, space the rows far enough
apart to
accommodate the kind of equipment used.
Three to four-foot
spacing (1-1.2 meters) for an animal-drawn cultivator and
three-foot
spacing (1 meter) for a power tiller are recommended.
Smaller-spaced
rows may be used with hand hoeing.
When mulch is used, the vegetables may be grown in beds
approximately
four feet wide with traffic paths in between.
All walking
is done on the paths so as not to compact the soil in the
beds.
Topsoil may also be dug from the paths and placed on the
beds to
increase rooting depth.
Although gardens are extremely labor intensive, cultivating
time
may be reduced by the use of machinery.
Manure spreading is the
hardest job.
Cultivating is much easier, however, if the manure
or compost is added in sufficient quantities, as the organic
matter will make the soil much easier to work.
The efficiency of
a garden can be greatly increased by irrigating during dry
periods. This will
ensure profitable yields in times when
drought might have made all the work a waste of time.
Row
plantings may be irrigated simply by allowing water to flow
between the rows.
Irrigating mulched beds may require more care
and possibly special equipment such as drip irrigation
systems.
However, the mulch helps retain soil moisture and so less
frequent
irrigation is necessary.
The cost of a garden should be kept as low as possible.
When a
garden is combined with a rotational system that includes
livestock, a steady supply of manure is available.
This
virtually eliminates fertilizer costs.
A heavily manured garden
will produce abundantly in a small area of space.
A small garden
will not require much machinery, keeping costs way down.
Maintenance requirements should also be low.
All machinery
should be lubricated properly and the surfaces of iron,
steel,
and leather items oiled regularly.
Hoes should be kept sharp for
fine weeding.
The best way to ensure a large supply of animal manure is to
keep livestock in a barn, corral, or other enclosure at
night.
Bedding straw retains urine and keeps manure drier.
This system
works exceptionally well with sheep or goats.
LAND USE SURVEY
All farmers should make a land use survey of their
farms. Many
farms are composed of both good and poor land, in one field
or in
several distinct fields.
Each field must be rated according to
slope, size, and soil type.
These factors will determine how
often and what type of crops are to be grown in each field.
Many acres-along narrow rivers have fertile level fields
next to
the river that can be cultivated every year.
As one moves away
from the river, a point is reached where the slope becomes
steeper and the land rises toward a hill.
These hillsides should
be used for livestock grazing and cultivated only at
intervals.
Each of the three major types of agriculture can show up on
a
farm. Farmers will
choose the type of agriculture and soil preparation
needed for each part of their farm.
SOIL PREPARATION EQUIPMENT
Soil preparation technology has developed as people have
built
bigger and bigger machinery.
However, the greatest mistake a
farmer can make is to buy machinery that is larger than the
job
that needs to be done.
Most gardens should still be worked by hand.
It is the lack of
manure and compost that makes the soil hard and leads
farmers to
think they need more equipment to work it.
Mixed livestock and
crop farming on sloping land needs no more than a small
tractor
or draft animals.
Only the huge farms and the most fertile,
level land can economically use today's large tractors.
The system of rotational agriculture was developed before
the
invention of the tractor and commercial fertilizer.
It is a
system in which plants and animals do most of the work of
preparing the soil for the production of crops.
Hence, it is
well suited to farmers who have little money to spend and
whose
land will not produce the grain yields obtained by prime
bottom
land farms where farm technology is at its peak.
Rotational livestock grazing systems require less equipment
than
cropping. The more
land grazed, the more manure is available for
the portion of land that is cropped.
REPLACEMENT OF NUTRIENTS
Growing plants absorb nutrients from the soil.
These nutrients
must be replaced, or the soil will lose its ability to
support
healthy plant life.
The major nutrients that have to be replaced
regularly are nitrogen, phosphorus, potassium, and
calcium. All
can be bought as commercial fertilizers, but they are also
found
in all kinds of vegetable matter and animal waste products
(see
Table 3). Many of
these resources can be obtained locally.
The best way to use plant wastes is to compost them.
Composting
breaks down fibrous vegetable matter and makes it easier to
mix
with the soil.
Bacteria and fungi digest large vegetable parts,
turning the material into a nutrient-rich fertilizer.
Compost
piles are made by alternating layers of plant wastes,
manure, and
a calcium source such as limestone or ash.
If the pile is kept
moist, the vegetable matter will be combined with manure and
calcium to form humus, a perfect source of plant nutrients.
Raw manure can be spread directly onto the field, but during
hot,
wet weather it should be worked quickly into the ground for
sanitary reasons.
Manure has an unpleasant odor but if properly
handled, it should not smell strong.
It also contains large
amounts of nitrogen which will be lost to the atmosphere if
not
worked quickly into the soil.
Table 3.
Nutrients Found in Vegetable and Animal Wastes
Source
Nutrient Supplied
Stable manure
Nitrogen, phosphorus,
potassium, calcium
Human waste
Nitrogen, phosphorus,
potassium, calcium
Waste vegetable parts
Nitrogen, phosphorus,
potassium, calcium
Leaves
Phosphorus, potassium,
calcium
Wood ashes
Potassium, calcium
Ground bones
Calcium, phosphorus
Ground shells
Calcium
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Manure and fertilizer need to be spread evenly over a
field. If
allowed to remain in piles, it can burn plants, stunting
their
growth. It may also
produce growth that is too rapid, causing
lack of buds, or lodging, in grain and vegetable plants that
are
all vine. Lime
should also be spread evenly to be of greatest
value.
III. FUTURE OF SOIL PREPARATION TECHNOLOGY
In the future, the mechanical processes used in agriculture
will
increasingly to be replaced by biological methods.
Over the past
10 years, the cost of machinery and replacement parts, fuel,
fertilizers, and other agricultural chemicals has doubled,
while
grain and livestock prices have remained stationary. Thus,
there
is an ever-increasing need for farmers to manufacture their
own
soil inputs. While
potassium and phosphorus may have to be purchased
or secured off the farm, the most important nutrient,
nitrogen, can be produced by the use of soil-saving legumes
and
manures.
More research is needed to develop new varieties of legumes
for
crop rotation or for companion cropping.
An ideal legume would
grow vigorously for a few months before the grain crop is
planted. Then the
legume would become dormant and act like a
mulch while the grain crop is growing, only to revive growth
after the grain is harvested.
Such a plant does not yet exist,
but legumes should be included in soil-building programs.
Properly suited legumes must be introduced to areas where
their
seed is difficult to purchase.
Legumes are also important to
soil conservation efforts.
Erosion is a world-wide problem, and
land too steep for continuous cropping should be placed in
pasture.
Legumes such as alfalfa provide excellent pasture while
they enrich the soil.
BIBLIOGRAPHY
Ensminger, M.E., and Olentine, C.G. Jr.
Feeds and Nutrition.
Clovis,
California: Ensminger Publishing Co.,
1978.
Hughes, H.D.
Forages. Ames, Iowa:
Iowa State University Press,
1966.
Russell, F. Walter.
Soil Conditions and Plant Growth. London,
England:
Logmans Green and Co., Ltd., 1961.
Archer, Sellers G.
Soil Conservation. Norman,
Oklahoma: University
of Oklahoma
Press, 1969.
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