29) Write a short paragraph on harmful effects of microorganisms.
30) Cultivation of crops involves several activities undertaken by farmers over a period of
time. List out these agricultural practices and give a brief account each one
Answers
29) Some serious diseases like anthrax is also caused in animals by the microbes. Microbes also cause diseases of plants like blights in potatoes, sugarcanes, oranges etc. They also reduce the yield. Microbes grow on food products and render them unfit for consumption.
30) Basic Practices of Crop Production
▸ Preparation of Soil: Before sowing the crop seeds, the soil of fields is loosened and overturned.
This process is called ploughing or tilling. Ploughing causes ventilation of soil and makes it suitable for the growth of small organisms living in it.
▸ Plough: A large farming implement with one or more blades fixed in a frame, used to turn over and cut furrows in soil, is called plough. Plough may be made of only wood, wood and iron, and of iron only (Fig. 1.1).
▸ Ploughshare: The main cutting blade of a plough.
▸ Hoe: A tool which is used for removing weeds and for loosening the soil.
▸ Cultivator: Nowadays ploughing is done by a tractor driven cultivator. The use of cultivator saves labour and time (Fig. 1.2).
▸ Sowing of Seeds: For sowing, farmers obtain certified seeds from State Agriculture Department and Seed Corporation. Sometimes, farmers also select seeds from their own crop. For selection of seeds of most of the crops, seeds are put into a bucket of water. The seeds which float on water are rejected. These seeds are defective. The seeds which remain submerged in water are selected for sowing. The selected seeds are treated with chemicals such as agrosan or ceresan. This chemical treatment protects seedling from seed-borne diseases. Seeds are sown either by hand-broadcasting (spreading) or by seed drills . A type of seed drill, commonly used, is a long iron pipe having a funnel at the top. It is tied at the back of the plough .
A farmer does ploughing and simultaneously releases seeds from the funnel. Seeds thus released pass through iron pipe to the soil furrows which are formed by the plough.
▸ Adding Manure and Fertilisers: Like other plants, crop plants also obtain their mineral nutrients from the soil. Continuous growing of crop in the field causes deficiency of mineral nutrients in the soil. So, the manure is added to the soil to make up the deficiency of mineral nutrients. This process is called manuring. Manure is prepared from cow dung, urine and other wastes.
Sometimes, soil becomes deficient in a particular mineral nutrients. This happens when same crop is grown in the same field year after year. For example, a particular crop takes more phosphate. If this crop is grown in a field every year, the soil will become deficient in phosphorus nutrient. This type of deficiency of a particular nutrient is made up by adding chemical substances called fertilisers. For example: urea, super phosphate and NPK (Nitrogen, Phosphorus, Potassium).
▸ Irrigation: The supply of water to crops at different intervals is called irrigation. The time and frequency of irrigation varies from crop to crop, soil to soil and season to season.
• Methods of Irrigation
▸ Traditional methods:
— Moat (pulley-system) — Chain pump — Dhekli — Rahat
▸ Modern methods:
— Sprinkler system — Drip system
• Protection from Weed
The unwanted plants in the fields are called weeds. Seeds of these weeds spread through the agencies like air, water, birds and other animals. Weeds share water, sunlight, space, nutrients with the crop plants. Thus they compete with the crop plants. Therefore, their removal is necessary. Otherwise, crop plants do not get sufficient space, water, sunlight and nutrient to grow healthier. Weeds are weeded out either by hand or with the help of an implement called harrow. Nowadays, for checking the growth of weeds, certain chemicals are used. These chemicals are called weedicides, such as 2, 4-D.