These are the CBSE class 9 biology notes on chapter Improvement in food resources
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:
- Mixed cropping
- Crop rotation
The practice of cultivating two or more crops simultaneously on the same piece of land is called mixed cropping. During mixed cropping, if one crop faces adverse conditions or pathogen attack then the other crop can be saved.
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:
- Crops should have different maturation time.
- Both crops should have different water requirements.
- The nutrient requirement of one crop should be lesser than the other.
- If one crop is deep rooted, the other has shallow roots.
- If one crop is tall, other should be dwarf.
- Increase in yield
- Optimum utilization of soil
- Minimum pest infestation
- No risk of crop failure
- Farmers can harvest varieties of produce at the same time
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:
- It helps to maintain the soil fertility.
- It makes better use of resources.
- It economizes space and time of cultivation of two or more crops.
- Each group can be harvested, threshed and marketed separately.
- Since the seeds of the two crops not mixed before sowing, fertilizers can be placed as per the need of the crops.
The practice of growing different crops on the same piece of land in a preplanned succession is called crop rotation.
Depending upon the duration, crop rotation is classified as:
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:
- Availability of moisture through rain or irrigation.
- Status of nutrients in the soil
- Availability of inputs such as fertilizers, pesticides, human power and machine power
- Duration of crop-short or long
- Marketing and processing facilities.
- Fertility of soil maintained for longer period.
- The chemical nature of soil is not altered.
- It helps in weed and pest control
- It saves a lot of nitrogen fertilizers.
Crop protection management:
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).
How are weeds harmful to crops:
Methods of weed control:
- They compete for food, space and light. Weeds take up nutrients and reduce the growth of the crop.
- Weeds may produce toxic substances which may interfere with crop growth.
- During harvesting, weeds get mixed up with crop to lower down its quality.
- The weeds spread crop pests and diseases by acting as alternate host to insects and microorganisms.
Weeds can be controlled by following methods:
These include the following methods: uprooting, weeding with towel or khurpi, hand hoeing (scrapping), interculture, ploughing, burning and flooding.
They include proper bed preparation, timely sowing of crops, intercropping and crop rotation.
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.
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:
- They cut the root, stem and leaves (Chewing insects).
- They suck the cell sap from various parts of the plants (Sucking insects).
- They bore into the stem and fruits (Internal feeders).
Thus, they affect overall health of the crop and reduce yield.
Preventive measures of insect pests:
Control of insect pests:
By using pesticides:
- Clean cultivation
- Optimum time of sowing the crops
- Use of pest resistant varieties
- Crop rotation and multiple cropping
- Cultural practices
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.
Storage of grains
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.
Factors affecting stored food:
There are two main factors responsible for losses during storage. These are:
- Biotic factors: The living organisms which influence the stored grains are called biotic factors. These are insects, rodents (e.g., house rat, house mouse, etc.), birds (e.g., sparrow, bulbul, crow etc.), mites and bacteria.
- Abiotic factors: The non-living environmental factors are called abiotic factors. These are moisture contents, humidity of air, improper temperature etc.
These factors causes degradation in quality, loss in weight, poor germinability, discolouration of produce, poor marketability and economic loss.
Preventive and control measures to be used before storage of food grains:
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- Drying: The harvested food grains should be dried by spreading them over plastic sheets or on cemented floor. All the sun dried food grains are allowed to cool to the room temperature before storing them.
- Cleaning and maintenance of hygiene: The grains and other agriculture produce should be properly cleaned before their storage. They should be filled in new gunny bags before keeping in godowns, warehouses or stores. The bags should be absolutely dry and clean. They should be free from dirt, webbing.
- Safe and proper storage: Godown, warehouses and stores should be properly cleaned, dries and repaired.
- Fumigation: Those pesticides which can destroy insects by forming toxic fumes are called fumigants and process of their use is called fumigation. Fumigants may be solid, liquid or gaseous. Examples:
- Aluminium phosphate (solid fumigant)
- Ethylene dichloride-carbon tetrachloride (EDCT) (liquid fumigant)
- Methyl bromide (gaseous fumigant)