ICSE Class 8 Biology Chapter 10 Food Production and Management I

Food Production And Management - I

Microorganisms and Plants

Syllabus

Useful microorganisms and plants - products obtained from them.

Agriculture: cash and food crops; rabi and kharif crops, annuals, biennials, perennials, orchards - examples of the same. Different types of soil - which is most suitable for crops (revision) - acidic and alkaline soils - how to treat them.

Agricultural practices: soil preparation, selection and sowing of seeds, irrigation, manuring - natural and artificial fertilisers, weeding, harvesting and storage of grain. (in brief).

Crop protection - pesticides/insecticides - useful and harmful effects.

Crop rotation - organic farming.

Visit, if possible, to agricultural areas to observe the steps taken by farmers.

Experiments to observe the water-retention capacity of different types of soil (E).

Testing soils for acidity/alkalinity (E).

Finding about pesticides used by gardeners - extension activity.

Making compost in the school garden.

Vermiculture - setting up a small unit in the school garden.

Interaction with agricultural scientists.

Introduction To Food Production

Food is the prime need of all living beings. Animals, including human beings eat either plants and plant products or feed on animals and animal products.

Originally, human beings were living in jungles and led a nomadic life. They knew nothing about agriculture or animal keeping. They used to hunt wild animals and ate them raw, but gradually they started roasting them on fire before eating. They also ate roots, leaves or fruits of different plants.

With the passage of time, man changed from the food-gatherer to the food producer. Besides growing crops, he also started breeding animals. Today, he gets food from several sources.

In this chapter, you will learn how microorganisms and plants are being utilised for getting food and other useful things.

Microorganisms

Microorganisms are those organisms which cannot be observed by the naked eye. They are extremely small in size and can be seen only under a microscope. They are also called microbes. The science which deals with the study of such organisms is called microbiology. Most of these organisms are unicellular e.g., viruses, bacteria, algae, fungi and protozans. Microorganisms are found everywhere - in air, water, soil, food (milk, curd, vegetables, fruits) etc. Generally, microbes are harmful as they cause different diseases like cholera, malaria, dysentery, tetanus, anthrax, etc., bue some microbes are useful to us in many ways.

Do You Know?

Microbes were the first living organisms to appear on the earth. Leeuwenhoek, the father of microbiology, was the first to describe the shapes of bacteria found in rain water and saliva of mouth.

Bacteria - General Structure

Bacteria are very small in size. They are of various shapes - round (coccus), rod-shaped (bacillus), spring-shaped (spirillum) and comma-shaped (vibrio). A bacterial cell is very simple in structure. It is surrounded by a wall and, has a primitive nuclear material (chromatin fibres) without a nuclear membrane. A bacterial cell has a slimy, gelatinous, protective layer in the form of a capsule. There is a thin cell membrane, below the cell wall, within which the cytoplasm along with some granules is filled. Certain bacteria move with the help of a thread-like structure called flagellum.

Fig. 10.1 Bacterium (highly magnified)

Important Uses Of Microbes

1. Increase in soil fertility. Bacteria decomposes the dead remains of plants and animals to form humus of the soil. Certain bacteria pick up nitrogen from the air and convert it into nitrites and nitrates which increase the soil fertility.

2. Nitrogen-fixing bacteria. In the roots of leguminous plants like pea, gram and pulses, bacteria found in the nodules of the root help in fixing free nitrogen of the soil into soluble nitrites which are useful fertilisers.

3. Decomposers and scavengers. Fungi and bacteria are decomposers and natural scavengers. They help in converting complex substances into simpler ones which are useful for the growth of plants. For example, nitrogen-fixing bacteria in the root nodules of leguminous plants.

4. In industry. Microbes are used in the preparation of medicines, beverages, food, textiles, etc. in the manner explained below.

(i) Antibiotics. Penicillin, streptomycin and aureomycin are some very useful antibiotics which are manufactured with the help of microbes.

(ii) Curd and Acids. Curd is produced by Lactobacillus, acetic acid by Acetobacter, and oxalic acid and citric acid by certain fungi.

(iii) Yeast is used in distilleries for the fermentation of fruit juices, malt grains or molasses ("sheera") to make alcoholic drinks. In the bakery, yeast is used to raise the dough for making bread.

(iv) Animal skins and hides are treated with bacteria to remove flesh and make them soft for tanning.

(v) Retting bacteria help in separating the fibres of the stem, e.g., flax and hemp.

(vi) Decomposition of hydrocarbons: Many bacteria such as Pseudomonas are capable of breaking hydrocarbons of the oil spills in marine and fresh water.

5. Sewage disposal. Many bacteria help in biological degradation of organic matter. Biogas used for cooking is being produced from human and animal excreta through bacterial activity.

6. Helpful in nutrition. Many bacteria live in our intestines where they synthesise certain 'B' vitamins. In the intestines of herbivorous animals like a cow a buffalo, bacteria help in the digestion of cellulose.

Mushrooms - Large-Sized Relatives Of Microorganisms

Certain varieties of mushrooms (button mushroom) are eaten as food. They are highly nutritive and rich in proteins. Some mushrooms of wild nature are not to be eaten, because they may be poisonous. Therefore, always buy mushrooms from a reliable shop.

Fig. 10.2 A poisonous mushroom

Agriculture - Primary Food Source

Agriculture is the backbone of human existence. Agriculture is defined as the science of growing food crops and other crops useful to man.

Primitive man, who was dependent for his food on animals, soon learnt how to cultivate plants. Prehistoric man lived on berries, tapioca (kand-mool), yam, juicy herbs, etc. To start with, as an agriculturist, man cultivated those plants which could be used as food, such as cereals, pulses, oil seeds, etc. With industrialisation, he used modern scientific practices like irrigation, fertilisers, better seeds and plant protection, which resulted in better production. To meet the increasing requirement of the fast growing human population, we need both extensive and intensive agriculture.

The cultivated crops can be classified under two categories:

1. Food crops: Crops cultivated for the production of food are called food-crops such as cereals, pulses, oil-seeds, etc.

2. Cash crops: Crops cultivated for commercial purposes are called cash-crops, such as rubber, tea, coffee, spices, etc.

Crop Plants

The plants grown and cared in the field for other useful products and harvested, annually or seasonally, are known as crop plants. The edible parts obtained from them may be in the form of grains, roots, vegetables and fruits.

Crop Plants Grown In India

Cereal crops - Rice, wheat, barley

Pulses - Beans, gram, peas

Oil crops - Groundnut, mustard, sunflower

Root crops - Sweet potato

Tuber crops - Potato, tapioca

Sugar crops - Sugarcane, beetroot

Plantation crops - Coffee, tea, rubber, coconut

Fibre crops - Cotton, jute

Plant Nutrients

Plants too require nutrients as we need, for their good growth. Such nutrients are carbohydrates, nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, copper, zinc, manganese, chlorine, etc. Some are required in traces (micronutrients) and some in large amounts (macronutrients). The deficiency of any nutrient in the soil affects the crop yield. The three most important nutrients for plant growth are nitrogen, phosphorus and potassium (NPK). Such requirement of nutrients is met by using chemical fertilisers and manures in the soil.

Horticulture

Horticulture is a branch of agriculture, in which we grow vegetables, fruits and decorative plants.

Horticulture Crops

Vegetables - Cabbage, cauliflower, spinach, tomato, etc.

Fruits - Mango, grapes, apple, banana, etc.

Decorative plants - Crotons, coleus, ferns, bougainvillea.

Decorative Flowers - Rose, gladiolus, sunflower, jasmine, etc.

Nutrients In Crops

Cereals are rich in carbohydrates and starch;

Pulses are rich in proteins;

Nuts, coconut and mustard are rich in oils.

Fruits and vegetables provide minerals and vitamins in particular.

Food Crops

A. Kharif Crop (means "autumn crops"): Kharif crops are raised in the rainy season (July to October). Rice is the most important kharif crop in India which occupies the largest area. Rice requires a temperature of 16-20-C during the growing season and 18-32-C during ripening. It needs rainfall from 150-200 cm, and needs flooded field during the growing period.

Soil for kharif crop. The paddy crop ideally grows on alluvial loam with a subsoil of clay. River valleys and deltas are most suitable for its cultivation. It can also be grown on hill slopes.

Cultivation methods for kharif crops

(i) Broadcasting is by throwing seeds over the soil.

(ii) Dibbling is dropping seeds at regular intervals in the furrows made by a plough.

(iii) Drilling. In this method, seeds are sown inside a hole made in the soil with a bamboo shaft or a long iron tube having a funnel into the furrow made by a plough.

(iv) Transplantation. In this method, seeds are first sown in nurseries after soaking them for 24 hours in water. When the seeds grow into tiny plants (seedlings), they are transferred to the seed bed in a nursery. Only healthy ones and well-developed seedlings are then picked up and transplanted to the regular field. This is called transplantation. This work is done in flooded fields.

Sufficient water supply or timely rainfall, good soil fertility, adequate use of fertilisers, use of different seeds and proper methods of cultivation provide a rich yield.

B. Rabi Crop (means "winter crop"): Wheat is important rabi crop of India. It is grown in alluvial soils of northern plains. Wheat is sown in October/early November. Winter rains are very important for the wheat crop.

Temperature for the wheat crop should be cooler (10-C to 15-C) and a warm and sunny weather is essential at the time of ripening. It requires a rainfall of 50 to 100 cm during the growing period. A little rain before crop grain ripens, helps to swell the grain.

Soil for rabi crop. Clay loamy soil or even black cotton soil is suitable. Some amount of lime in the soil is beneficial.

Cultivation method for rabi crop. Seeds are sown both by broadcasting and under dibbling (a pointed tool for making holes in the soil for seeds) and drilling. Sowing is done soon after the rainy season because there is enough moisture in the soil to help the growth of the plant in the first few weeks. The grain is formed by the end of January and the rising temperatures help to ripen the crop.

Three Categories Of Plants On The Basis Of Their Life-Span

Plants can also be classified on the basis of their life-span into three categories.

Annuals. Annuals are those plants which complete their life cycle in one year or one season, e.g., wheat, rice, gram, beans, pea, sunflower or most of the seasonal flowering decorative plants and vegetables. After the seeds are formed, the whole plant except seeds die.

Fig. 10.4 Some annual plants

Biennials. Biennials are those plants which live for two years or two seasons, e.g., beet root, radish, turnip and carrot in temperate regions of the world. In the first year, the plant bears vegetative parts and in the second year, it bear flowers, fruit and seeds. Some plants in tropical climate, like some plants in tropical climate, like in India, complete their life cycle in one year only. Some such plants are, turnip, potato, carrot, etc.

Fig. 10.5 Some biennial plants

Perennials. These are the plants which live for more than two years and they bear flowers and seeds every year, e.g., rose, pine, mango, teak, guava, etc. Some plants live for hundreds of years like banyan, peepal, pine, etc. Bodhi tree of Sri Lanka is more than 2000 years old. Some pine trees in America are over 4000 years old.

Fig. 10.6 Some perennial plants

Orchards

Orchards are the areas where fruit trees are grown in closed boundaries, e.g., mango, litchi, apple, orange, etc. Fruit trees are propagated vegetatively by the method of stem grafting and layering.

Soil

Agricultural production depends upon the quality of soil. Soil must be fertile and it should contain nutrients in sufficient quantity as required by plants. It should be able to retain water. Also, it should not be too acidic or too alkaline.

Soil is a mixture of minerals, decay matter (organic remains), humus, water and air. It also contains many living organisms like the bacteria, fungi and worms. Soil formation is a very slow process. It takes thousands of years to form. It occurs due to physical, chemical and biological processes. Disintegration of rocks into smaller fragments occur due to high temperature, cooling, wind and water. Composition of soil depends upon the parent rock from which it has formed. Soil composition keeps changing due to pollution and decay of organic matter and by the addition of manures and fertilisers.

Types Of Soil

Soil is broadly classified in the following three types:

1. Sandy soil. It contains more sand (90%) and less clay (10%). It is permeable to air and water due to large pore spaces which dry up very easily. It is suitable for fruits and vegetables.

2. Clayey soil. It has a high portion of clay. It becomes sticky in water. It is not aerated (air spaces). Roots find difficulty in penetration and it gets waterlogged in high moisture. It becomes suitable for farming by adding sand and lime.

3. Loamy soil. It is a mixture of sand and clay together with silt and humus. It is most suitable for plant growth.

Activity 1

To observe the water-retention capacity of different types of soil.

Take three types of soil - clayey, sandy, and loamy in equal amounts. (You can get loamy soil from the flower bed, sand from the place where some construction work is going on, and clay from the hobby-room of your school where clay-modelling is practised, or from a potter).

Dry the soil samples and keep them in separate funnels (A, B, and C) lined with wet filter paper.

Place these funnels on the top of measuring cylinders.

Gradually, pour 100 mL of water in each funnel.

After about one hour, read the level of water in each cylinder.

Record your observations in a table given below:

Conclusion

Funnel A with clayey soil has passed ............. mL of water (fill in the blanks by actual reading) and retained ............. mL. The amount of water retained is more than that has filtered out. Thus, clay has more water-retention capacity.

Funnel B (sandy soil) has passed ............. mL of water at a faster rate. Thus, the sandy soil has very little water-retention capacity (.............. mL).

Funnel C (loamy soil) has passed more water than that in A and less than that in B. Thus, loamy soil has moderate water-retention capacity (................ mL).

Properties Of Soil

Soil should have the following characteristics:

1. Water-holding. The soil should have a proper water holding capacity but, not waterlogging.

2. Air. The soil should be well aerated. Good air holding capacity helps the roots to respire.

3. Texture. Soil texture should be such that water and air can pass through its particles.

4. Acidity and alkalinity. Excess of acids or alkalis in the soil is harmful.

5. Nutrients. The soil must have both macro and micro nutrients in their proper quantities. C, H, N, P, K, Ca and Mg are macronutrients, while Mn, Cu, Zn, Cl, Fe and Mo are some micronutrients. These are needed for the fertility of soil. All these nutrients are found in the soil in the form of salts.

If a field is used for growing the same crop again and again, then the soil fertility reduces. Then, either the field should be left unused for one or two seasons for the activity of micro-organisms to replenish the soil nutrients or manure and fertilisers can be used to enrich the soil. Crop rotation is also a method to replenish soil nutrients. In this method, leguminous plants are grown in rotation alternately between two cereal crops. Leguminous plants contain nitrogen fixing bacteria in the root nodules which help in fixing free nitrogen of the soil into soluble nitrates.

Teacher's Note

Soil is the foundation of agriculture and food production. Understanding soil types helps farmers choose appropriate crops and improve yields in their local gardens.

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