SOIL AND WATER CONSERVATION ENOTE

WEEK EIGHT

SUBJECT: AGRIC SCIENCE

CLASS: GRADE 8

TERM: SECOND

TOPIC: SOIL AND WATER CONSERVATION

Conservation is regarded as planned use of any natural resource to avoid exploitation, neglect and destruction. Soil conservation is the use of the soil without waste so as to sustain higher crop production or yields. It is aimed at preventing waste of the soil and depletion or loss of its nutrients. Soil conservation is important because plants depend on nutrients in the soil. Animals indirectly depend on the soil for their feed. It is the soil that provides the medium for plant growth and development and hence the sustainer of life.

METHOD OF SOIL CONSERVATION

One of the most modern methods of conserving the soil on extensive tracts of farmland is the use of contour bonds or ridges. The trend or slope of such land is determined with a precision instrument called (a) line level (b) dumpey level (c) precision level and other kinds. The intervals between the contour lines are determined by: (i) the type of soil (ii) the gradient or steepness of the slope (iii) the size of the farm tractors to be used.

Other methods of soil conservation are

(a) Crop rotation: This is a system of planting different types of crops on the same piece of land such that they follow one another in definite order. Example: planting of maize in 2003, groundnut in 2004, yam in 2005 and cowpea in 2006 of the same farm.

(b) Application of organic manure: Organic manure includes farmyard manure, poultry manure, compost manure, and green manure.

(c)  Application of inorganic manure: Inorganic manure is fertilizers, which are chemically synthesized in the form of powders, crystals or pellets to correct certain deficiencies in the soil.

(d) Bush Fallowing: It is the process of leaving a piece of land to rest and regain its fertility, after a thorough use.

(e) Liming: It is the addition of lime to the soil.

(f) Planting of cover crops: This is the process by which certain crops that are leguminous in nature are planted to provide a protective cover over the soil. Examples are melon, mucuna, centrosema and puereria.

(g) Mulching: Mulching is a method used in preventing evaporation or evapo-transpiration by the placement of straw, leaves, saw-dust, etc on the surface of the soil.

WAYS BY WHICH PLANTS NUTRIENT ARE LOST (EROSION)

(a) Leaching: This is the removal of nutrients out of the reach of plant roots by percolating water. It is common in areas with heavy rainfall, loose soil particles and sparse vegetation, primary nutrients such as nitrogen, phosphorus and potassium are lost under high rainfall condition. They dissolve easily in water and go down the soil profile.

(b) Crop removal: Soil nutrients are used by crops for growth and development. Farmers harvest crops such as tubers, seeds, fruits and vegetables. These are used by man for food and other purposes. The nutrient taken up by these plants are lost completely from the soil. This is because the harvested parts of crops are not returned to the soil through decay.

(c) Burning: The burning of vegetation reduces soil fertility. This is because it exposes the surface of the soil to the agents of erosion such as water and wind. Soil micro-organisms of agricultural importance are killed during burning. There is also break down of volatile nutrients like sulphur and nitrogen.

(d) Erosion: Soil erosion causes loss of soil nutrients. When the top soil of farmland is removed by water or wind the available plant nutrients are lost. Erosion is common in soil that is not covered by vegetation.

(e) Oxidation and reduction: Oxidation and reduction reactions in the soil lead to loss of soil nutrients. For example ammonium elements in the soil can be oxidized to give ammonia gas. Nutrients such as nitrates may be reduced to nitrogen gas or nitrogen dioxide gas. The gases go into atmosphere resulting in loss of fertility.

ASSIGNMENT

Objective Questions:

1. Soil nutrient can be lost through A. contouring B. fertilizer application C. liming D. leaching E. nitration

2. The following are methods of replenishing plant nutrients in the soil except A. continuous cropping B. cover cropping C. crop rotation D. fertilizer application E. mulching

3. The washing down of plant nutrients beyond the root zone is referred to as A. erosion B. flooding C. logging D. leaching E. percolation

4. The washing away of top soil is known as A. denudation B. drainage C. erosion D. evaporation E. leaching

Theory Questions:

1. What is soil conservation?

2. List four methods of soil conservation and explain two.

3. List and explain three ways in which plant nutrients are lost.