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Supply of organic matter

An acre of living topsoil contains approximately 900 pounds of earthworms, 2,400 pounds of fungi, 1,500 pounds of bacteria, 133 pounds of protozoa, 890 pounds of arthropods and algae, and even small mammals in some cases. Soil also contains dead organisms, plant matter, and other organic materials in various phases of decomposition. Humus, the dark-coloured organic material in the final stages of decomposition, is relatively stable. Both organic matter and humus serve as reservoirs of plant nutrients; they also help to build soil structure and provide other benefits.

Organic matter and humus are terms that describe different but related things. Organic matter refers to the fraction of the soil that is composed of both living organisms and once-living residues in various stages of decomposition. Humus is only a small portion of the organic matter. It is the end product of organic matter decomposition and is relatively stable. Humus contributes to well-structured soil that, in turn, produces high-quality plants.

Practically all the soil organisms depend on organic matter as their food source. Therefore, to maintain their populations, organic matter must be renewed from plants growing on the soil, or from compost. When soil livestock are fed, fertility is built up in the soil, and the soil will feed the plants. Rich organic matter and humus levels help to maintain favourable conditions of moisture, temperature, nutrients, pH, and aeration.

Nutrient supply

The nutrients most necessary for proper plant growth are nitrogen, potassium, phosphorus, iron, calcium, sulphur, and magnesium, all of which usually exist in most soils in varying quantities. In addition, most plants require minute amounts of substances known as trace elements, which are present in the soil in very small quantities and include manganese, zinc, copper, and boron. Nutrients often occur in the soil in compounds that cannot be readily utilized by plants.

Exercise 5. Think of the questions to which the following sentences are answers:

1. Soil management involves six essential practices: proper tillage; maintenance of a proper supply of organic matter in the soil; maintenance of a proper nutrient supply; control of soil pollution; maintenance of the correct soil acidity; and control of erosion.

2. The purpose of tillage is to prepare the soil for growing crops.

3. Among the secondary but important benefits of tillage is the aeration resulting from pulverization.

4. Traditional tillage may harm the soil if used continuously over many years.

5. An acre of living topsoil contains approximately 900 pounds of earthworms.

6. Soil also contains dead organisms, plant matter.

7. Humus is only a small portion of the organic matter.

8. Rich organic matter and humus levels help to maintain favourable conditions of moisture, temperature, nutrients, pH, and aeration.

9. The nutrients most necessary for proper plant growth are nitrogen, potassium, phosphorus, iron, calcium, sulphur, and magnesium.

10. Trace elements include manganese, zinc, copper, and boron.

 


Date: 2015-12-17; view: 268


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