Class 8 Crop Production and Management - Basic Practices of Crop Production

Q: Given below are statements about the harmful effects of weeds on crop plants.(i) They interfere while harvesting.(ii) They help crop plants grow healthily.(iii) They compete with crop plants for water, nutrients, space, and light.(iv) They affect plant growth.Choose the correct statements from above.

Harmful effects of weeds on crop of plant are as follows:They interfere in harvesting.They compete with crop plants for water, nutrients, space and light.They affect plant growth.Presence of weeds increases the cost of agriculture and hinders the progress of work.It increases the irrigation requirement.They reduce the value of produce or otherwise adds the cost of cleaning.Some weeds when eaten (Cleome viscosa) by milch animals will produce an undesirable odour in the milk. At times death/disorder/deformity may occur. For example, Datura stramonium.The fruits and seeds of Xanthium strumarium and Achyranthes aspera entangle with wool which fetch lower prices.They harbour insect pests, pathogens and parasites.They reduce the value of the land.Presence of weeds will impair the purity of varieties by chance of cross pollination.Weeds cause health hazards to man and animals.Weeds cause allelopathic effect.Therefore, the correct answer is option A.

Q: What are the advantages of ploughing?

A plough is a tool or farm implement used in farming for initial cultivation of soil in preparation for sowing seed or planting to loosen or turn the soil. Ploughs were traditionally drawn by working animals such as oxen and horses, but in modern times are mostly drawn by tractors. The process of loosening the soil for cultivation is called ploughing. The primary purpose of ploughing is to turn over the upper layer of the soil, bringing fresh nutrients to the surface, while burying weeds and the remains of previous crops and allowing them to break down. The advantages of ploughing are:Loosening of soil can improve air circulation.The roots can penetrate deeper into the soil, thus holding the plant firmly.Ploughing enhances the water retention capacity of the soil.Ploughing uproots the weeds growing in the field and aids in the growth of useful microbes.

Q: Discuss various methods for weed control.

Weeds are unwanted plants which grow along with the crop plants in cultivated field and cause reduction of crop yield.The different methods of weed control are :(a) Mechanical methods : Weeds can be removed by uprooting by hand or by using trowel.(b) Cultural methods : By employing timely sowing of seeds in properly prepared beds, intercropping and crop rotation methods, weed growth can be minimized.(c) Chemical methods : Weeds can be destroyed by spraying chemical called weedicides. (d) Biological methods : Certain insects and crop plants prevent the growth of weeds.

Q: Weeds affect the crop plants by

Weeds are unwanted plants in the cultivated field. They compete with the crop plants for food, space and light. They take up the nutrients and reduce the growth of the crop.

Q: Write a short note on the following :Preparation of soil

Preparation of soil: Preparation of the soil involves loosening and turning the soil. This process is known as ploughing, is done by using a wooden or iron plough which pulls the soil. The pulled soil is then levelled by using a wooden or iron leveller.

Q: Why is organic manure considered better than fertilizers?

Organic manure or organic fertilizer is made up of organic biodegradable waste like animal excreta and agriculture wastes. As it biodegradable it cannot harm the environment and increase the soil fertility it is better than chemical fertilizer. But chemical fertilizers are nutrient specific and prepared in chemical factories. Thus, the correct answer is option C.

Q: Beera, wants to practice crop rotation in his field. Suggest a Rabi crop and a Kharif crop which will replenish his field with nitrogen. Which crop replenishes nitrogen and why?

Explanation of the answer.Rabi crops are ones that are grown at the end of the monsoon or the beginning of winter that includes gram, pea, and linseed. Kharif crops are the ones that are grown in the monsoon that includes arhar, groundnut, and soybean.These crops belong to the family of Fabaceae. These plants share a symbiotic association with bacteria such as rhizobium. These bacteria fix nitrogen from the atmosphere and help in replenishing the nitrogen.

Q: Unwanted plants growing along with crop plants are called ________.

The unwanted plants which grow in field along with the crop plants are termed as weed. They are harmful for the crops as they compete for nutrients with them.

Q: Read the statements given below and choose the correct statements.(i) Seeds require moisture for germination.(ii) Plants can absorb nutrients mostly in dissolved form.(iii) Irrigation protects the crops from both frost and hot air currents.(iv) Irrigation improves soil texture.Choose the combination of statements which indicate the need to irrigate crops.

A dormant seed contains only 10-15% of water and is essentially dehydrated. The seed has to absorb water in order to become active. Plants grow by absorbing nutrients from the soil and all the nutrients have to be in the dissolved form.Irrigation does not always improve soil texture. Irrigation does not protect the crops from frost. Irrigation is the artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall.Thus the correct answer is option A.

Q: The process of loosening and turning of soil is called:

The process of loosening and turning of soil is called tilling or ploughing. This is done by using a plough, hoe, or cultivator.The soil is loosened to increase the absorption of water and manures.It improves soil quality by increasing aeration. It controls the weeds. Therefore, option C is correct.