soil types. Ask students to bring soil from their farm, back yard,
cottage, etc. in an air tight container. Also bring in a small supply
of peat moss, sand, some commercial potting soils, and compost. Compare:
- the texture,
(rub a soil sample in your fingers)
- particle size,
(using various grades of screens)
found in each. (use microscope)
(mass by volume),
- water content,
(weigh sample and allow to dry, weigh again)
- and water
retention abilities. (pour a fixed amount of water through a soil
sample in a cylinder and time how long it takes to percolate to
- Test each
for pH levels. Check with school science department for additional
soil test equipment and supplies.
- Ask students
to describe attributes of each sample.
Divide class into
groups and have them research one of the following:
- What are
the soil classifications. Research the predominant soil types in
your region. (One source is the Canada Land Inventory, see resource
guide) Have this group prepare a report on findings, including
their findings on the type of agriculture most common in the region.
Ask students to identify which farming approaches are used in their
region. If they have better alternatives, present with reasons why
it is better for their region.
agricultural practices in the region. Have this group talk to federal
and provincial (or State) departments of Agriculture, to representatives
of organizations like the Prairie Farm Rehabilitation Administration,
grower groups, and individual farmers in their region. Urban students
could include green houses and nurseries in this list. Develop a
list of questions with students to ask farmers and government officials.
Include questions which explore such issues as:
of organic matter
extent of topsoil depletion since farming started
impact of wind and water erosion and the effectiveness of
shelter belts and other forms of erosion control
- the impact
of irrigation, where it's used and its long term effects
and their role in the health of agriculture in the region
- energy use
- Have group report
on their findings.
which have influenced farming practices.
- Have students
discuss how economic factors have affected the quality of the soils
in their region. Ask them to suggest how to promote a healthy environment
and farm economy. Have group report on their findings.
- What is
the diversity of agriculture in the region the students live? Ask
students to explore how agricultural practices in their region affect
human health and well-being. Have students consider how the type
of soil in their region might determine the nature of the agricultural
practices and how these in turn affect human activity.
on the region, this group could explore diversity in agriculture
such as market gardening, ranching, grain farming, fruit-growing,
or row-crop farming. Ask group to investigate links between the
health of the soil, agricultural use of the soil, and the well-being
of the economy and society. Have group report on their findings.
Using this information, challenge your class to identify how agricultural
practices in their region might affect other regions.
Based on the research
above, have students describe the best use of soil resources in their
region. Can these resources be described without considering water
and climatic resources? Ask them to build a description which includes
a consideration of economic, environmental, and the health and well-being
for the region.
Plants need a
balanced diet to be healthy. To grow, plants use nutrients and water
from the soil, carbon dioxide from the air, and sunlight. Some basic
nutrients in the soil are readily available to plants. Others are
made available by organisms in the soil. For example, nitrogen, the
most important soil borne nutrient, is made usable by nitrogen fixing
bacteria in the roots of leguminous crops, such as peas, beans, lentils,
alfalfa and clover, and by decomposing organic matter. Other nutrients
needed by plants include phosphate, potassium, and trace elements
such as iron, copper, boron, and zinc.
Plants store energy
from one season to the next in a number of ways. Some make tubers
in the ground, like potatoes, others create bulbs, like onions or
garlic. Many plants drop leaves and then absorb the nutrients from
the decomposing leaves in the following seasons. The flow of nutrients
from growth to decay and back to growth again is called the nutrient
cycle. When a tree drops its leaves; or a plant dies; or an animal's
remains are left after it has died; or it has been devoured by a pack
of wolves, digested and excreted, the processes of decay return these
nutrients to the soil. Plants cannot eat a dead moose or a fallen
log until it has been broken down into usable forms. Fungus and bacteria
eat organic matter and excrete nutrients back to the soil. Plants
feed on these nutrients and in turn, these plants are consumed by
animals, who eventually die, perhaps from being devoured by wolves
When soil is low
in the required nutrients, there will be a low crop yield with possible
poor nutritional content, unless this deficiency is corrected. Fertilizers
can be used to correct the shortfalls. They work by introducing nutrients
directly into the soil.
are mineral based compounds containing nutrients necessary for plant
growth. Chemical fertilizers are readily available in a wide variety
of formulations and are easily applied with the right equipment. They
have been designed for many different applications and can be formulated
to match existing soil conditions.
chemical fertilizers do not significantly renew organic matter in
the soil, so the prolonged use of chemical fertilizers alone may result
in a decrease of both organic material and biological activity in
the soil. Over time, this can result in a reduced capacity to produce
crops. Therefore farmers must use other methods to maintain organic
matter in their soil, such as summer fallow, crop
rotation, or using additional inputs.
The high solubility
of synthetic fertilizers can result in nutrient imbalances in the
soil and run off absorbed into the ground water. They also
require the use of non-renewable resources, and considerable amounts
of energy, for their extraction, production and transportation.
naturally occurring sources contain nutrients in more stable forms
which are less prone to run off and often have considerable active
microbial populations. However, run off of either synthetic or natural
fertilizers can pollute ground water and cause eutrophication. We
have to take care with the storage and application of both.
come from a variety of sources. These include:
- the recycling
of wastes such as manure, wastes from slaughterhouses and packing
plant materials and microbial cultures of beneficial species.
requires better soil care than simply the replacement of used minerals
with fertilizers. Crop rotation can also provide a cost effective
way to grow fertilizer. This can enhance soil microbial activity,
and replace consumed organic matter and nutrients. Taking land out
of production, called fallow, allows it time to regain lost
nutrients. Green fallow employs a cover crop to protect the
soil from erosion and increase the organic matter. It is preferred
to black fallow which leaves the soil uncovered and prone to
erosion and damage from the sun.
draw different nutrients from the soil. Planting the same crop in
the same field, year after year (monocrop agriculture), depletes the
nutrients that plant requires and results in less productivity. The
planned changing of crops on a given field is called a crop rotation.
This varies the draw of nutrients from season to season and so allows
for nutrients to be replenished naturally. Rotation and use of leguminous
plants such as beans, lentils, and alfalfa allows farmers to create
their own nitrogen in the soil, while producing a marketable crop.
degradation is the depletion of the productive capability of Canada's
precious soils and is a costly problem.
- It is estimated
that erosion of 2.54 cm (one inch) of soil can reduce wheat yields
by 100 to 233 kilograms per hectare (1.5 to 3.4 bushels per acre).
- In Southwestern
Ontario, the erosion problem has caused a loss in corn yields of
some 30 to 40 percent.
- lands affected
by salinization in the Prairies, crop yields have been reduced by
10 to 75 per cent.
- It is estimated,
at 1982 prices, that it would cost the farmers $239 million in fertilizer
to fully recover the present loss of grain production from wind
and water erosion.
- More difficult
to put a dollar figure on, but equally as serious, is the permanent
loss of rich agricultural land to urban use. Between 1961 and 1976,
Canada lost more than 1.4 million hectares (3.5 million acres) of
farmland - the equivalent of the size of Prince Edward Island.
at Risk, Canada's Eroding Future, A Report on Soil Conservation by
the Standing Committee on Agriculture, Fisheries, and Forestry, to
the Senate of Canada, 1984, Ottawa pp3-4. Note: Values originally
in Imperial, converted to Metric.
Soil erosion can
occur when wind or water sweep away the topsoil.
The dust bowl
of the "dirty thirties" was a result of sustained drought
with poor agricultural practices. Huge clouds of blowing topsoil turned
the sky dark, clogged the water systems, and made the air unbreathable.
There are a variety
of methods farmers use to combat erosion. Some plant tree wind rows
to reduce the effect of wind on the fields, and others leave stubble
on a field after the crop is harvested, to bind the soil together.
The practice of zero-tillage reduces soil erosion by eliminating ploughing
and any other tillage. Planting crops in the direction opposite the
natural water run-off pattern decreases water erosion.