Soil - Free MCQ Test with solutions, UPSC General Science

A soil's physical and chemical properties affect plant growth and soil management. Some important physical and chemical properties of soil are mineral content, texture, cation exchange capacity, bulk density, structure, porosity, organic matter content, carbon-to-ni- trogen ratio, color, depth, fertility, and pH.

Top soil contains organic matter. It is rich in humus which is rotting dead matter.

This is the most comprehensive way to classify soils, as it takes into account all three of the most important characteristics of a soil: its colour, texture, and mineral content. The colour of a soil can tell us about its fertility, texture can tell us about its drainage and aeration, and mineral content can tell us about its nutrient levels. By looking at all three of these characteristics, we can get a better understanding of the soil and how it can be used.

Dense vegetation helps in protecting the soil from erosion by water and wind.

minerals, organic matter, air and water

Clayey soil has highest water holding capacity as it is poorly aerated.

Layers of soil are called horizons.

Humus is dark, organic material that forms in soil when plant and animal matter decays.

Weathering is the breaking down of rocks, soil, and minerals as well as wood and artificial materials through contact with the Earth's atmosphere, water, and biological organisms.

Soil horizons differ from one another in composition (e.g. clay or organic matter content), physical properties (e.g. color or particle size), or chemical properties such as pH or CEC.

The region in which the tree has been uprooted or dug out shows the soil profile. We can see soil profile while digging a well, making deep cut out through soil and while laying foundation for building. 

The region in which the tree has been uprooted or dug out shows the soil profile.We can see soil profile at the sides of roads on a hill or at a steep of river bank.

The top most layer is also called the humus layer, which is rich in organic material. This layer consists of decomposed material and organic matter. This is the reason, the topsoil has a dark brown color. 

The top most soil has highest concentration of organic matter as a result it can retain more water, is soft and is porous layer.

Humus makes the soil fertile and provides nutrients to growing plants.

B-layer contains more minerals and lesser amount of humus.

Sandy Soil is light, warm, dry and tend to be acidic and low in nutrients. Sandy soils are often known as light soils due to their high proportion of sand and little clay.

Loamy soil is best for growing plants. 

Clayey soil is used to make pots and toys.

The soil most suitable for cotton is Sandy loamy soil. And thus, black soil is considered best for growing cotton. The farmers sows’ seeds of cotton in the month of March till early june.