Page 70 - Introduction to Agriculture by: Aqleem Abbas

Introduction to Agriculture Notes prepared by: Aqleem Abbas

incorporate nitrogen from the air into the soil (see Nitrogen Fixation), enriching the soil and reducing the need for nitrogen-
containing fertilizers. Crop rotation also conserves nutrients. For example, the roots of the first crop may be near the surface and
the second crop’s roots may be deeper, so that nutrients are drawn from different depths in the soil.

Soil held in place by plant roots is less likely to blow or wash away, or erode, than bare soil. Organic farmers minimize soil
erosion with cover crops—short-lived plants, often grasses or legumes—that protect the soil between the harvesting of one crop
and the planting of the next. Many organic farmers also conserve soil by practicing no-till or low-till farming, avoiding the use of
plows to turn the soil, or using implements that only slice or slightly turn the soil. They may also leave the unharvested portion of
a crop in the field to cover the soil, preventing soil erosion from wind or rain.

Pest management in organic farming

Conventional farms rely on an array of synthetic pesticides to kill weeds, disease-causing fungi, and harmful insects. These
pesticides are manufactured by chemically processing petroleum, natural gas, ammonia, and a number of other raw materials.
They include active and inactive ingredients, both of which can be highly toxic and long lasting. Organic farmers typically use
pesticides primarily derived from chemically unaltered plant, animal, or mineral substances in which the active toxic ingredient
breaks down rapidly to become nontoxic after being applied to the crop. Pyrethrum (a substance extracted from the
chrysanthemum), a variety of soaps, and oil from the neem tree are among the insecticides used by organic farmers. Bordeaux
mix, a combination of calcium carbonate and copper, is used by organic farmers to control disease-causing fungi.

In addition to using natural pesticides, organic farmers control pests by planting different crops in wide, alternating bands, a
technique called intercropping. This approach interrupts the movement of disease-causing organisms through a field, since many
insects and fungi feed on just one type of crop. Organic farmers also reduce insect damage by spraying crops with bacteria that
kill larvae (immature insects) and planting crops that attract ladybugs, lacewings, and other beneficial insects that prey on
unwanted insects.

Organic farmers use many methods for weed control. Mulching involves covering the soil around crops with straw or other
materials that smother weeds. Cover crops can be planted in the fall and turned under in a few months; they help control weeds
by competing with them—an oat crop, for example, grows faster than weeds and deprives them of the nutrients they need to
produce seeds. Other types of cover crops, such as cereal rye, release substances from their roots that inhibit weed seed
germination. Organic farmers sometimes use a variety of tractor-drawn equipment to uproot weeds that emerge with crops.

Organic farming is sometimes referred to as sustainable agriculture, although the two concepts have subtle but significant
differences. Sustainable agriculture seeks to improve the entire food and agricultural system by balancing production and
consumption. For example, a farmer practicing sustainable agriculture may use the manure from the animals to fertilize the fields
of grain that are grown to feed the animals. Eliminating the purchase of fertilizer reduces the cost of growing grain, and growing
grain for animal feed rather than buying it reduces the cost of raising livestock.

Sustainable agriculture also addresses the environmental, economic, and social issues related to agricultural systems. It attempts
to ensure that arable land is protected so that current and future generations will be able to farm it successfully; many involved in
sustainable agriculture also seek to preserve the vitality of family-owned farms and rural communities. A sustainable farm may
not be organic, and an organic farm may not be sustainable, although they may use similar techniques.