How wheat is grown. Care during growth

Wheat grows in a wide range of climates and soils. But a good wheat crop requires suitable weather and proper soil. To achieve the highest yields, wheat farmers must use high-quality seed that is free from disease. Farmers also must plant and harvest the wheat at just the right time. In addition, they must protect the growing crop from damage caused by diseases and pests.

The basic steps for growing wheat are much the same all over the world. However, wheat farms differ in size and levels of mechanization (work done by machinery). In many nonindustrial countries, wheat farmers use animals to pull their plows across small plots. They also may plant and harvest their crops by hand, in industrialized countries, nearly all the wheat is grown on large farms with the aid of tractors and specialized machinery. This section describes how wheat is grown on a large, mechanized farm.

Plowing the field is the first step in preparing the soil for planting wheat. The plow turns and loosens the earth to aid in planting. Plowing also makes it easier for the seeds to sprout and grow

Climate conditions. Fairly dry and mild climates are the most favorable for growing wheat. Extreme heat or cold, or very wet or very dry weather will destroy both spring and winter wheat. Weather conditions, including temperatures and rainfall, influence when wheat is planted. Planting seeds too early or too late reduces the yield. Late planting of winter wheat also increases the chance of damage from cold.

Farmers plant winter wheat in time for the young plants to become hardy enough to survive the winter cold. Winter wheat is planted as early as September 1 in Montana and as late as November 1 in Texas, where cold weather arrives much later. In northern winter wheat areas, farmers may plant wheat in furrows (narrow channels) a few inches deep. These furrows fill with blowing snow, which acts like a blanket and protects the plants from extreme cold.

Spring wheat is exposed to fewer weather hazards because it has a far shorter growing period than winter wheat does. Farmers in northern Nebraska and South Dakota may plant spring wheat in early March. Farmers to the north—in Minnesota and North Dakota—may wait until mid-April to plant spring wheat.

Soil conditions. Wheat grows best in the kinds of soil called clay loam and silt loam (see Loam). The soil should contain much decayed organic (plant and animal) matter to provide food for the wheat plants, if the soil lacks some nutrients, a farmer may add these in the form of fertilizer.

In many parts of the world, farmers grow wheat on the same land every year. After many years, such land may lack the nutrients needed to produce a good crop. In addition, erosion by wind or water can remove nutrients from the soil. Farmers commonly have samples of soil tested to determine if the soil has the necessary nutrients. Such tests also indicate the amount of acid in the soil, if soil becomes too acid, wheat will not grow well and may not even sprout. Farmers can add fertilizer and lime to the soil to restore nutrients and reduce acidity.

Some farmers do not plant wheat on the same land every year. They may plant wheat in rotation with such crops as clover, corn, oats, soybeans, or timothy. This practice returns nutrients to the soil and helps control diseases and pests. In regions with little rainfall, farmers may plant a field every other year. Between wheat crops, they leave the field fallow (unplanted) so that it can store moisture.

Preparing the soil. Wheat farmers prepare fields for the next crop by plowing. They begin plowing as soon as possible after harvest. Plowing breaks up the soil surface and allows moisture to soak into the ground where it is stored for the next crop. It also buries weeds and the remains of the previous crop. This plant matter releases nutrients as it decays. In areas that suffer from erosion, farmers use a plow that loosens the soil but leaves plants on the surface. These plants help reduce erosion.

Just before planting wheat, farmers prepare the seedbed with a device called a spring-tooth harrow. Harrows have sharp metal spikes that break up chunks of earth into small pieces that can pack closely around the wheat seeds.

Planting. Farmers use a tractor-drawn machine called a drill to plant wheat seed. The drill digs furrows just deep enough to plant the seeds. At the same time, it drops the seeds, one by one, into the furrows and covers the seeds with soil. Some drills also drop a small amount of fertilizer with the seed. Drills can be set to plant the desired number of seeds per acre. Seeding rates range from about ½ bushel per acre (1.2 bushels per hectare) in dry regions to about 2 bushels per acre (4.9 bushels per hectare) in moist regions. With a large drill, a farmer can plant more than 200 acres (81 hectares) of wheat a day.

Planting wheat requires from ½ bushel to 2 bushels of seeds per acre (1.2 to 4.9 bushels per hectare). A machine called a drill, left, drops the seeds into the ground and covers them with soil

Care during growth. Growing wheat can suffer damage from diseases, insect pests, and weeds. Wheat farmers employ various practices to help prevent such damage.

Controlling diseases. The most destructive wheat disease is rust This disease is caused by a fungus that grows on the wheat plant and produces small, rust-colored spots on the leaves, stems, and heads. The spots later turn brown. The fungi draw food and water from the wheat plant. This action may prevent the kernels from developing. There are two types of rust, leaf rust and stem rust. To protect their wheat crops, farmers often destroy nearby barberry plants, on which the stem rust fungus must live during some stages of its growth. Some varieties of wheat are resistant to certain kinds of rust. Breeders continue to develop more varieties of wheat that can resist rust.

Another serious fungus disease that harms wheat kernels is smut The two main kinds that attack wheat are bunt(also called stinking smut) and loose smut Wheat kernels infected with bunt fill with a black mass of smut spores. These infected kernels are called smut balls. When smut balls break, they release a rotten, fishy odor. If smut balls break during harvesting, the spores spread and contaminate thousands of other kernels. If infected kernels are sown, the next crop also will be damaged. In wheat plants infected with loose smut, black smut spores replace both the kernels and the husks. Wind carries these spores to other wheat plants, spreading the disease. Farmers can control both kinds of smut by treating the seeds before planting or by spraying their crop with a chemical that kills the spores. Some varieties of wheat can resist smut infection.

Several other diseases attack wheat, but in most cases they do not cause widespread damage. They include flag smut, glume blotch, leaf blotch, scab, take-all, black chaff, and mosaic. Controlling insect pests. Insects damage about 10 per cent of the United States wheat crop every year. More than 100 different kinds of insects attack wheat. Some, including grasshoppers and locusts, eat the stems and leaves of the wheat plant. Wireworms, cutworms, and some other insects eat the roots and seeds or cut the wheat stem at the surface of the soil. Still other insects, including Hessian flies, suck sap from the stems. Insects that damage wheat also include army worms, cereal leaf beetles, green bugs, jointworms, wheat stem sawflies, and wheat stem maggots. Grain weevils and Angoumois grain moths attack stored wheat grain.

Some varieties of wheat are resistant to Hessian flies and wheat stem sawflies. Farmers can control other insect pests by using insecticide sprays. Planting winter wheat after the Hessian flies that hatch in the fall have died also helps farmers to reduce the crop damage caused by this insect pest.

Controlling weeds. Weeds rob wheat plants of moisture and nourishment. This loss reduces grain yields. Certain weeds can spoil a wheat crop. For example, wild garlic and wild onions give wheat an odor that makes it unfit for use as flour. Other weeds that cause serious damage to wheat crops include Canada thistle, cheat, field bindweed, Russian thistle, wild morning glory, wild mustard, and wild oats. Careful preparation of the seedbed helps prevent the growth of weeds. If weeds become a problem among growing wheat plants, farmers may apply chemicals that have been approved for such use by government agencies.

Harvesting. Farmers harvest wheat as soon as possible after it has ripened, before bad weather can damage the crop. Wheat is ready for harvest when moisture makes up no more than 14 percent of the weight of the kernel. To check for ripeness, farmers may take a sample to a grain storage elevator for moisture testing. Farmers also may test wheat by biting a kernel or breaking it with their fingernails. When ready for harvest, the kernels are hard and brittle and break with a sharp, cracking sound.

Large mechanized farms use huge, self-powered machines called combines to harvest wheat. Combines cut the stalks and thresh — that is, separate the kernels from the rest of the plant In North America, large teams of combines follow the wheat harvest north from Texas to Canada. These combine teams move from field to field, operating day and night to harvest the wheat on time.