These are the CBSE class 9 biology notes on chapter Improvement in food resources Topics covered in this page are
In order to get maximum benefits from the piece of land, different pattern of growing crops are followed. These are:
Objective of mixed cropping: The basic objective in mixed cropping is to minimize the risk and insure against the crop failure due to abnormal weather conditions.
Crop-combination used in mixed cropping: some important combinations used by farmers during mixed cropping:
Wheat + Mustard
Groundnut + Sunflower
Wheat + Gram
Cotton + Moong bean
Barley + Chick pea
Criteria for the selection of crops during mixed cropping:
Advantages of mixed cropping:
The practice of growing two or more crops simultaneously in a same field in definite row pattern is called intercropping. The row pattern may be in the ratio of 1:1, 1:2, and 1:3. It means after one row of main crop, one, two, or three rows of intercrops can be grown.
Objective of intercropping: The basic objective in intercropping is to increase the productivity per unit area.
Advantages of intercropping:
Depending upon the duration, crop rotation is classified as:
One-year rotation: Rice-Wheat, Maize-Mustard
Two-year rotation: Maize-Mustard-Sugarcane-Fenugreek, Maize-Potato-Sugarcane-Pea
Three-year rotation: Cotton-Sugarcane-Pea-Maize-Wheat, Rice-Wheat-Mung-Mustard-Sugarcane-Berseem
Selection of crops for rotation: Most commonly, legumes are included in the crop rotation programme. They are used to increase soil fertility.
Those crops which require high fertility level (e.g., wheat) may be grown after growing legumes (e.g., pea). Thus, high input crops such as sugarcane, potato, maize, wheat and rice may be grown before low input required crops. Thus while making selection of crops for crop rotation, the following points should be considered:
Advantages of crop rotation:
Crops plants are infested by large number of weeds, insect pests and diseases. If these weeds, insect pests and diseases are not controlled at appropriate time, they can damage more than 50% of the crop produced.
Weed and weed control: Weeds are unwanted plants in the cultivated field. For example, Xanthium (Gokhroo), Amaranthus (Chaulai), Parthenium (Gajar ghas), Chenopodium (Bathua), Avena sativa (Wild oat).
Methods of weed control: Weeds can be controlled by following methods:
Mechanical methods: These include the following methods: uprooting, weeding with towel or khurpi, hand hoeing (scrapping), interculture, ploughing, burning and flooding.
Culture methods: They include proper bed preparation, timely sowing of crops, intercropping and crop rotation.
Chemical methods: Destroying the weeds by spraying special chemicals called weedicides like 2,4- D (2,4-dichlorophenoxy acetic acid), MCPA (2-methyl, 4-chlorophenoxy acetic acid), Atrazine and Butachlor.
Biological methods: It involves the deliberate use of insects or some other organisms which consume and specifically destroy the weed plants. For example, cochineal insects are used to eradicate the weeds called Opuntia (prickly pear).
Insect pests and their control: Insects which destroy or damage crop plants are called insect pests. All crops are attacked by insect pests.
Insect pests attack the plants in three ways:
Thus, they affect overall health of the crop and reduce yield.
Preventive measures of insect pests:
Control of insect pests:
By using pesticides: The chemical used to eliminate pests are called pesticides. Pesticides include insecticides (for killing the insects), weeedicides (for killing the weeds), rodenticides (for killing rats), and fungicides (for killing the fungi).
By using natural insecticides: Like neem, nicotine, pyrethrum, etc.
Most crops are harvested only once a year. Thus, they are available in plenty during a selective time. For getting seasonal foods regularly throughout the year, they are stored in safe storage. During storage, grains and seeds are subjected to spoilage and wastage by various means. This loss has been estimated to be 9.3% annually.
There are two main factors responsible for losses during storage. These are:
These factors causes degradation in quality, loss in weight, poor germinability, discolouration of produce, poor marketability and economic loss.