Module 2 Lesson 1

The plant-soil-water system

Major components of soil in relation to plant

Describe composition and function of soil in crop production

Soil is a collection of natural bodies occupying portion of the earth’s surface. It supports plants and have properties due to the integrated effect of climate and living matter.

Functions of soil:

It is storehouse for plant nutrients;
It is a medium for growing crops;
It provides the crops with essential plant nutrients in addition to water and oxygen for root respiration; and
It provides plants with essential nutrients.

There are four major components of soil namely mineral, air, water and organic matter.

Click on the organic and mineral parts of the graph to view its composition

pie

The organic matter of the soil
The organic matter constitutes only between 1% and 6% of the weight of the topsoil in upland soils. Organic matter gives the soils their dark color. An average ideal soil consists of only about 5% (by weight) organic matter, which is composed of a wide range of organic (carbonaceous) substances, including living organisms (the soil biomass), and carbonaceous remains of organisms. Organic matter also increases the amount of water a soil can hold for plant growth.

The mineral composition of the soil
The mineral matter in the soil (which is about 45% by volume of the average soil) is a complex mixture of solid mineral materials. The soil inherits mineral matter from its parent rock and organic matter from its living organisms. These materials constitute the solid portion of the soil and form its skelet

Next Lesson

Now that you can describe the composition of soil, we can now proceed with the forms of soil-water.

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