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Agriculture food supply and population in our environment

RELEVANCE OF BIOLOGY TO AGRICULTURE
Biology is the stdy of living things Agricuitun the growing of plants and the rearing farm animals to provide our needs the cultural activities a basic knowledge of biology is necessary. Such knowledge includes

. the structure, function and nutrition of plants and animals

* diseases which affect plants and animals and the organisms which cause them ;

* ecological systems
*soil ; and
* genetics.


Classification Of Plants

Plant can be classified in several ways. In Botany (the study of plants), all plants are grouped into the plant kingdom and subdivided as on pages 15 to 20. This classification, which is based mainly on structure, function and evolu- fo
tionary trends, is not particularly useful to a farmer. However,more useful and appropriate ways of classifying plants include grouping them

. into annuals, biennials and perennials; and
. for agricultural purposes.

Annuals, Biennials and Perennials Plants are commonly grouped into annuals, biennials and perennials according to the span of their life cycles.

This classification applies mainly to flowering plants, the group to which most crop plants belong.

It is a practical way of classifying crop plants as it helps a farmer to
plan how to use his land to meet his goals.

Annuals These plants complete their entire life cycles and die within one growing season which may be from a few months to a year.

Many im-portant agricultural plants are annuals. Examples include rice, wheat, maize, bean, flax, jute and sunflower


Biennials These plants grow and store food during the first growing season, and use it in the second growing season to produce flowers, fruits and seeds before they die example include cabbage, radish and turnip which are harvested for food immediately after the first growing season.

Perennials These include trees, shrubs and herbs which continue to grow from year to year producing flowers, fruits and seeds for many years. Agriculturally important perennials include herbaceous ones such as ginger and onion, and woody ones like rubber, oil palm, cacao, mango and coconut.

Agricultural Classifications
In agriculture, cultivated plants or crops are usually grouped according to the products for which they are grown as given below

Cereals These plants belong to the grass fam
ily. They include maize, rice millet, Guinea corn and wheat. They are grown for their
grains which form the bulk of the world's food supply. The grains have a high starch content and contain varying amounts of proteins, oils and vitamins.

The legumes are an important source of dietary protein. They also supply
protein-rich fodder for livestock in tropical countries. In addition, legumes replenish soil nitrogen because nodules on their roots contain nitrogen-fixing bacteria. This makes them important in crop rotation. Legumes include bean, groundnut, cowpea, soya bean, oil bean,Legumes lima bean and yam bean.

Root crops They are grown mainly for starch and form the staple food of the people in many tropical countries. They include cassava, yam and sweet potato.

Vegetables Various kinds of vegetables are grown to supply dietary vitamins and certain minerals like calcium. Examples include to-mato, okra, onion, pepper and spinach.

Fruits Many plants are grown for their fruits which are rich sources of vitamins, especially vitamins A and C, minerals and sugars. Most fruits are eaten raw. Examples include orange pineapple, banana, plantain, mango, pawpaw and native pear.

Beverages and drugs The crops which yield ese products include cacao, coffee, tobacco and quinine. The products, cocoa and coffee,

are food drinks; tobacco is a stifnulant; and quinine is used as a medicine.

Spices Pepper, ginger, cinnamon and cloves belong to this group. They are used mainly for flavouring food.

Oils The fruits and seeds of certain plants are rich in oil. Such oil crops include oil palm, Shea butter, coconut and sunflower.

Forage crops These are the grasses and leg-umes that are grown for animal feed.

Latex When a cut is made on the trunks of certain trees, a. milky fluid called latex flows out. The rubber tree is grown in tropical coun-tries for its latex which is used to make natural rubber.

Fibres Plants such as jute, hemp and cotton are grown for their fibres which are used for making ropes and cloth.

Soil
Soil is very important in agriculture. It provides anchorage for plants. It also supplies water and mineral salts that are essential for their nutrition. Animals, including humans, depend on plants for food, and as such, indirectly depend on the soil.

Soil characteristics
Most sails are made up of a misture of sand silt and chay with varying amounts of humus

A sandy aoti has very little humus Since the particles in a sandy soll are large, it has a
oarse lesture wüh plenty of space between the particles Hence, it is well aerated but water dvains through it quiekly leaving it dry. It is not a good suil tor erop culivation

A clayey soil is made up of very fine parti-cles with very little space in between them. Asa result, it becomes easily water logged during the wet season and is poorly aerated, During the dry season, it hardens and cracks. It is also not a good soid for erop cultivation

Loamy soil contains a misture of sand and clay particles with plenty of humus. It has a good crumb structure which allows water to drain through it while holdi!男back just enough for plant growth It is well aerated and rich in plant nutrients. This is the best type of soil for crop cultivation

Soil Erosion
Brosion is the wearing away and removal of fertile topsoil from an area by the wind and water (during a heavy rainfal).

Plants cannot
grow on eroded land. Erosion is, therefore, a serious problem as it affects the economy of a country that depends on agriculture for sup-plying its needs Erosion is often due to bad farming prac-tices such as overgrazing of pastures, continual cropping without fallowing or adding fertiliz-ers, and exposing soil surfaces for long periods Farmers can prevent erosion by good farming practices.

This includes the following:
Growing fast-growing cover crops in be-tween slow-growing crop plants such as oil
palms. Cut grass and crop residue can be spread over bare ground to protect it. This
is known as mulching.
Contour ploughing or ploughing along the contour of the land to reduce water runoff.

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