Solutions for Class 8 Science Chapter 1 Crop production and management

 

Exercise

1. Select the correct word from the following list and fill in the blanks. float, water, crop, nutrients, preparation (a) The same kind of plants grown and cultivated on a large scale at a place is called _____________. (b) The first step before growing crops is _____________ of the soil. (c) Damaged seeds would _____________ on top of water. (d) For growing a crop, sufficient sunlight and _____________ and _____________ from the soil are essential. Ans: (a)crop. (b) preparation  (c) float  (d) water and nutrients  2. Match items in column A with those in column B.             A B (i) Kharif crops  (a) Food for cattle (ii) Rabi crops  (b) Urea and super phosphate (iii) Chemical fertilisers            (c) Animal excreta, cow dung urine and plant waste (iv) Organic manure (d) Wheat, gram, pea   (e) Paddy and maize Ans:- A B (i) Kharif crops  (e) Paddy and maize. (ii) Rabi crops  (d) Wheat, gram, pea. (iii) Chemical fertilisers  (b) Urea and superphosphate. (iv) Organic manure (c) Animal excreta, cow dung urine and plant wastes.   3. Give two examples of each. (a) Kharif crop (b) Rabi crop Ans: Kharif crops- Paddy and maize Rabi crops- Wheat and gram 4. Write a paragraph in your own words on each of the following. (a) Preparation of soil (b) Sowing (c) Weeding (d) Threshing Ans: (a) Preparation of soil : Soil preparation is the first step in agriculture before planting a crop. Soil preparation is done to loosen the soil, allowing the roots to penetrate deeper into the soil. This allows the roots to breathe more easily. The fertile soil allows for the growth of worms and microorganisms, which will help to keep the soil fertile by adding compost to the soil. Loosening the soil brings soil full of nutrients up to so that plants can use these nutrients. Loosening the soil also brings nutrient-rich soil to the surface, which is essential for plant growth. (b) Sowing : Sowing is an important process in crop production. First, healthy seeds are selected before sowing. After selecting healthy seeds sowing is done by traditional methods or by using seed drilling machines. (c) Weeding : Removal of unwanted plants from the field is called weeding. Weeds compete with crop plants  for nutrients and water. This will reduce the yield of the desired crop. Manual methods such as physical weeding are used to remove weeds. Weeds are also controlled by the use of certain chemicals, called weedicide. (d) Threshing : The process of separating the chaff is called threshing. Threshing is carried on a machine called ‘combine’ which is a harvesting and threshing machine. The threshing is also performed by means of a wind blower (winnowing) that separates the chaff from the crop.  5. Explain how fertilisers are different from manure. Ans: S.N Fertilizer Manure  1 Fertiliser is a man-made obtained inorganic salt.  Manure is a natural substance, prepared from organic matter such as human waste, cow dung and farm waste  2 Fertiliser is prepared in  factories.  Manure can be prepared in the fields.   3 Fertiliser does not provide humus to the soil Manure provides a lot of humus to the soil.  4  Fertilisers are very rich in like nitrogen, nutrients. phosphorus and potassium.  Manure is relatively less rich in plant plant nutrients. 6. What is irrigation? Describe two methods of irrigation which conserve water. Ans: The supply of water to crops at regular intervals is called irrigation.  Methods of irrigation  (A) Sprinkler system -This method is more useful in uneven land where sufficient water is not available. Perpendicular pipes, with rotating nozzles at the top, are connected to the main pipe . When water is allowed to flow through a main pipe under pressure with the help of a pump, it escapes through the rotating nozzles. It is sprinkled on the plant as if it were raining. (B) Drip Irrigation- In this method the water goes drop by drop directly into the roots this method is very useful where where availability of water is poor. . 7. If wheat is sown in the Kharif season, what would happen? Discuss. Ans: Kharif comes during the rainy season so wheat crops may be destroyed if planted during the Kharif season due to unfavorable temperatures and  conditions .  8. Explain how soil gets affected by the continuous plantation of crops in a field. Ans: Plants need nutrients to grow. Without good nutrition the plants will die. Regular cropping leads to a reduction in certain nutrients such as Nitrogen, Phosphorus, Potassium etc. This leads to a decrease in yield  so there must be a gap between the plants in order to get a good yield. 9. What are weeds? How can we control them? Ans: In the fields many other undesirable plants may grow naturally along with the crop. These unwanted plants are called weeds. Weeds can be controlled by a method called weeding. Tilling before sowing helps to uproot and kill weeds, which can be dried and mixed with the soil. Weeds are also controlled by the use of certain chemicals, called weedicide. 10. Arrange the following boxes in proper order to make a flow chart of sugarcane crop production. Ans:  11. Complete the following word puzzle with the help of clues given below. Down 1. Providing water to the crops. 2. Keeping crop grains for a long time under proper conditions. 5. Certain plants of the same kind grown on a large scale. Across 3. A machine used for cutting the matured crop. 4. A rabi crop that is also one of the pulses. 6. A process of separating the grain from chaff. Ans :