NCSU's Agronomy Department
What is agronomy and why should you be interested?
Agronomy is the study of plants, soil and their environment. At NCSU's agronomy department we focus on sustaining the worlds food production, protecting the quality of the environment, and conserving vital soil and water resources. Scientists say that food production has increases greatly over time, but many people still go hungry every day, and malnutrition is responsible for the death of over more than 5 million children every year. All these problems start with soil, and soil starts with us.
What's in the soil and how does it get there- Weathering
There are 2 kinds of weathering- physical and chemical. Physical is the actual breakup of rock. Out of that kind there are 5 kinds of physical weathering. First, freezing and thawing: when ice gets inside a crack, freezes and expands. Root growth is pretty much the same: a root grows in a crack, the rock breaks apart. Abrasion is when sand that is carried by a force wears away rock. Release of pressure is when little pieces of rock flake off. The last is caused by animals. They dig, the rock breaks. Chemical is different. There are 4 kinds of chemical weathering. Oxidation is oxygen+ water + iron = rust. Second there is carbonation. CO2+ rainwater= carbonic acid. Third is acid rain. Weathering takes place very quickly. Last is when roots of plants make a weak acid that breaks down the rock around it.
Soil composition, texture, and horizons
Soil composition is basically what the soil is made of. Normal soil is made of humus, sand, silt, clay, minerals, rock, air, and water. Soil horizons are the different layers of the soil all together. Top layer: humus. Middle layer: Topsoil. Lower layer: Subsoil. Bottom: Bedrock. Last is soil texture. Sandy or silty soils are light because they drain water. Clay soils hold water so they are heavier. A mixture of grains: loam. Scientists measure percents of sand, silt and clay using a triangular diagram.
Formation requires weathering and takes hundreds or thousands of years to form. The two most important factors in formation are climate and rock type. Soil develops better in a warm wet area because if you have more rain, it develops faster.
Remote sensing is observing a process or a substance without coming in direct contact with it. This is usually done from space, using satellites, scanners, and radar. This is used to monitor soil formation and movement.
Why is soil so important?
Soil is essential for growing food and purifying water and air. It filters out waste and toxic chemicals. Also, it acts as a home for animals.
Misuse of soil
A good example would be the dust bowl of the 1930's. Farmers overgrazed, and over cultivated the land, as well as doing deep drilling. During this time there was also severe drought and high winds, sweeping up the topsoil layer and blowing the dust everywhere. This is one excellent way to misuse soil.
One way to conserve soil is to make terraces. In one country where they are farming using this method they are producing 5 times more food. To make a terrace, you cut steps into a hillside at different elevations. Another way to conserve soil is to rotate crops. This means putting the same plant families together in different spots each year. This will reduce the pests and diseases that infect the plants. Last, there is contour farming. This is where farmers plow around the base of the hill instead of up and down it.