Improvement of food resources of Class 9
Biofertilisers are micro-organisms(like bacteria, algae and fungi used singly or in combination) or biologically active products which are used to enrich soil fertility.
Some of the Biofertilisers are given below:
- Legume – Rhizobium symbiosis
- Azolla – Anabaena symbiosis
- Free – living bacteria (Azotobacter) living in soil symbiotically.
- Cyanobacteria (Anabaena, Nostoc)
- Mycorrhiza (symbiotic association of fungi with roots of higher plants.)
Modern agricultural production enormously uses chemical fertilizers and chemical pesticides. These agricultural chemicals are not always beneficial to the mankind as they cause some deteriorating effects on the environment and ecological stability.
Organic farming is a farming system with minimal or no use of chemicals. In this farming :
(i) The use of organic manures and biofertilizers are recommended. The organic manures help in recycling of farm-wastes. Biofertilizers are also harmless. They have the microbes which bring about soil nutrient enrichment, maximize the ecological benefits and minimize the environmental hazards. Some bio-agents like blue-green algae are used for this purpose.
(ii) Similarly, herbicides and pesticides are replaced by biopesticides (such as Neem leaves or turmeric especially during grain storage).
(iii) The organic farming also recommends the healthy cropping system in the form of mixed cropping, intercropping, etc.
An organic farm
Advantages of organic farming
- Natural ecosystem is not disturbed, as organic farming is in harmony with the natural ecosystem.
- Soil fertility is preserved.
- Harmful effects of chemicals on the living organisms are avoided.
- Pollution of air, water and soil does not take place.
- The basic objective of cropping is to achieve insurance against total crop failure under poor rainfall conditions and thereby minimizing risk and monetary loses.
Water, an indispensable treasure for life, is also a basic component for all types of agriculture. The soil becomes barren without water.
The basic source of water is rainfall and in India most of the agriculture is rain-fed. However, the monsoonal climate is erratic with respect to onset, intensity, duration, distribution and retreat. To avoid this, our agriculture needs an alternative arrangement of water supply called irrigation.
Thus, irrigation is defined as the application of water to the soil for the purpose of supplying moisture essential for plant growth especially during stress periods.
Intermittent drought and poor rainfall poses a serious threat to rain-fed farming areas. Under such conditions irrigation system is adopted to supply water from different water resources.
Some common sources of irrigation are :
- Wells : The ground water is an important source for irrigation from wells. Wells are of two types.
- Dug wells : They are open wells and get water from water bearing strata. They soon become dry whenever water table goes down and are generally owned by farmers privately.
- Tube wells : Privately owned shallow tube wells are mostly run by electrically operated or diesel operated pump sets. Deep tube wells have longer life period of 20 -25 years.
- Canal system : Canal system of irrigation is considered best because of its interrelation with a number of other aspects. For example, generation of hydroelectricity, flood control, mitigating drought and other hazards. Canals draw water from rivers or from artificial reservoirs. They are divided into branches and distributaries to cover maximum areas for irrigation.
- River lift system : In areas where canal system is a failure due to inadequate reservoir release, the river lift system is more rational. Water from the rivers is directly drawn to supplement irrigation in areas close to the rivers.
River lift system
In India there are three major types of rivers. They are:
- The Himalayan rivers : They are perennial rivers, e.g. the Indus, the Ganga, etc.
- The rivers of central India and deccan : They are seasonal rivers, e.g. Godavari, Krishna, Mahanadi, etc.
- Coastal river : They have ephemeral character.
- Tanks : These are water reservoirs where water is stored for irrigation, flood control, pisiculture, etc. They help in rain water harvesting and recharging ground water table.
Fresh initiatives for increasing the water available for agriculture include rain water harvesting and watershed management.
Rain water harvesting : Rain water is collected and recycled into ground by digging tunnels. This water percolates into the soil. Thus, the water table is maintained. It can also be poured into a well or used for filling ponds in low level areas.
Watershed management: Small check dams are built up in watershed areas to increase percolation of water into the ground, reduce flow of rain water to prevent soil erosion.
Advantages of irrigation : Irrigation has many advantages over reliance on natural water supplies:
- Water supplied by irrigation supplies hydrogen and oxygen elements to the crop plants.
- Irrigation of crops makes the soil moist, which is required for the germination of seeds.
- Irrigation loosens the soil and thus helps in elongation and growth of roots.
- Water dissolves the nutrients present in the soil. Dissolved nutrients are easily absorbed by the roots of the plants.
- Modern multipurpose dams not only provide water for irrigation but also control floods and generate hydroelectric power.
- Water supply by irrigation is reliable and regular whereas dependence on rainfall is seasonal and unpredictable.
Mixed cropping :
It is the practice of growing two or more types of crops simultaneously on the same piece of land. Different crops to be grown are selected in such a way that products & wastes from one crop can stimulate the growth of other crop.
Crop combinations used in mixed cropping :
- Growing wheat crop + gram
- Growing cotton crop + groundnut
- Growing groundnut +sunflower
- Growing ragi + gram
- Growing turmeric + groundnut
Selection of crops for mixed cropping : Following criteria are taken into account :
- Duration of crops
- Growth habit
- Root pattern
- Water needs
- Nutrient demands
Intercropping: Improved version of traditional mixed cropping in which two or more crops are grown simultaneously in the same field but in a definite row pattern is called intercropping.
Criteria to accomplish intercropping :
- spatial arrangement
- plant density
- maturity dates of crops
- plant architecture
Types of intercropping :
Row Intercropping : in this intercropping all crop combination of mixed cropping are used in definite row pattern 1:1, 1 : 2 or 1: 3.
Strip Intercropping : growing two or more crops simultaneously in strips, wide enough to permit separate crop production using machines.
Productivity is increased.
It economises spaces and time of cultivating two or more crops.
It helps to maintain soil fertility.
TABLE COMPARISON BETWEEN MIXED CROPPING AND INTER CROPPING
1. Aim is to minimize risk of crop failure.
Aim is to increase productivity per unit area
2. Seed of component crops are mixedBefore sowing.
Seed of component crops are not mixed.
3. Sowing is not done in rows.
Sowing is done in rows.
Crop rotation: The fertility of soil is reduced if one crop is grown in a field for several years. The soil shows deficiency of same type of nutrients. Also, the disease causing pathogens multiply and increase in number as they get their host every year. This can be avoided by growing different crops in a pre-planned succession. For example, a mustard crop is alternated with sugarcane which is again alternated with berseem or any other crop. Such type of planned alternate cropping is called crop rotation.
Depending upon the duration, crop rotation is classified as:
- One-year rotation: Rice – Wheat, Maize – Mustard.
- Two-year rotation: Maize – Mustard – Sugarcane – Fenugreek (methi), Maize – Potato – Sugarcane – Pea.
- Three-year rotation: Cotton – Sugarcane – Pea – Maize – Wheat, Rice – Wheat – Mung – Mustard – Sugarcane – Berseem.
Pattern of crop rotation
Advantages of crop rotation:
- Fertility of soil is 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:
The crop provides us the products of economic or commercial values and thus it becomes our prime duty to provide protection to crop plants from their enemies. The various enemies of our crop plants are:
Removal of weeds from the field is called weeding.
Undesirable plants which grow along the crop plants and compete with them are called weeds.
e.g., Amaranthus (chaulai), Chenopodium (bathua), Convolvulus (hirankhuri), Avena (wild oat), Cenchrus, (grass) etc.
There are over 30,000 species of weeds around the world, out of which 18,000 species are very harmful for crop plants.
Weeds deplete soil’s nutrients, water and light available to crop. As a result of this crop yield decreases.
They also interfere with agricultural practices. Sowing the seeds with seed drills is not possible in presence of weeds. Contamination of food grains with weed seeds such as Datura and Argemone is harmful to human health.
They produce unpleasent odour to flour. Weeds harbour so many pests which cause diseases in crop plants. They also harbour some organisms like mosquitoes that transmit the diseases to human beings.
Weed control method
There are many methods which are used to control weeds. However, there is no single method to control all types of weeds. We just apply a combination of methods at a time. Some of the common methods are discussed hereunder.
Cultural methods : Tillage, plantation, application of fertilisers and irrigation etc. come under cultural practices which help in controlling the weeds. Of these, tillage, fertiliser application and irrigation are important. They should be used in combination with other methods. These methods alone can not control weeds, but help in reducing their population.
Hand-weeding : Pulling out the weeds by hands or uprooting them with the help of small tools is known as hand weeding. This is a very common and effective method for most of the weeds growing in low density.
Hand-hoeing : This method is also very effective. In this method, the entire soil surface is dug to a shallow depth by hard hoes (Hoe is a tool which is used for loosening the soil). The weeds are easily uprooted by this method.
Digging : Weeds can also be removed by digging upto a certain depth. It is very useful in case of perennial weeds. Cynodon dactylon (doob grass) is removed by this method.
Mowing : By this method, weed plants are cut to the ground level. This method is usually practised in non-cropped areas, lawn and gardens. Repeated mowing weakens the underground parts of perennial weeds. The common mowing tools are sickle, saythe and lawn mower.
Burning : It is the cheapest, method to remove the weed plants. It is done in uncropped fields on road sides, field bunds and ditch etc. This helps in phosphorus enrichment of the soil.
Biological methods : In this method, Bio-agents such as disease causing micro-organisms, insects, birds and other animals are used to control weeds. They infest the weeds and reduce their growth or even kill them. Thus, the population of weeds is controlled.
In India and Australia, over-growth of cacti was controlled by cochineal insect (Cactoblastic cactorum). This insect is the source of a biological stain called carmine used for colouring the chromosomes. Recently, in California a weed named Hypericum perforatum has been controlled by a beetle called Chrysolina.
Motha (Cyperus rotundus)
Bathua (Chenopodium album)
Jangali jaii (Wild oat)
Chaulai (Amaranthus viridis)
Harmful pests of our crop plants are small insects which attack the plant in 3 ways:
- Chewing insect : They cut the root, stem and leaf and swallow these pieces of plant parts. e.g. Locusts.
- Sucking insects : They suck the cell sap from various parts of the plant with the help of their needle like hollow mouth parts, e.g. Bugs.
- Internal feeders : They bore into seeds and fruits, live inside and harm the crop yield, e.g. Borers.
Preventive measures against insect pests:
- Clean cultivation : Many soil-borne diseases can be prevented by proper selection of site and pesticide treatment of seeds before sowing.
- Optimum time of sowing the crops : Attack of pests can be avoided in areas and during time-periods where pest is ineffective due to environmental conditions.
- Use of pest resistant varieties: Pest resistant varieties can be developed by hybridization.
- Summer ploughing : If we plough the soil in summer and sowing of seeds is done after some time, then the seeds would be less susceptible to the attack of pests.
- Crop rotation and multiple cropping : Pests are very specific about the host crop plant which they attack. When host crop is altered with non-host crop, insect infestation can be checked.
- Cultural practices : Distance between plants, depth of sowing, time and amount of irrigation, time and methods of planting are some of the cultural practices which can check the insect pests to much extent.
Control of insect pests
- By using pesticides : The chemicals used to eliminate pests are called pesticides. Pesticides include insecticides (for killing the insects), weedicides (for killing the weeds), rodenticides (for killing rats), fungicides (for killing the fungi).
- By using natural insecticides : Like neem, nicotine, pyrethrum, etc.
- Biological method of pest control : In this method, some insects, birds or some other organisms are deliberately left in the affected crop fields to kill the pests selectively, e.g., Australian ladybirds were left in citrus orchards to control the scale insects in California, U.S.A.
Disease causing agents (pathogens):
Many pathogenic organisms like fungi, bacteria, viruses, nematodes, etc, damage the plants and reduce the yield. These diseases are infectious and can be transmitted through soil, water and air. Some of these diseases are epidemic and cover a large area of population resulting in severe outbreak.
Depending upon their mode of occurrence, crop diseases are of following four main types:
- Seed-borne diseases : These diseases are spread through seeds, e.g., “ergot of bajra” or of pearl millet, “leaf spot of rice”, “loose smut of wheat” – all are caused by fungi.
- Soil-borne diseases : These diseases are spread through the soil and mostly affect roots and stems of crop plants, e.g., “smut of bajra, “tikka disease of groundnut”.
- Air-borne diseases : These crop diseases are transmitted by the air, e.g., “rust of wheat”, “blast of rice”, etc. Air-borne diseases attack all aerial parts of the plants, e.g., leaf, flower, and fruits.
Water-borne diseases : Pathogens of these crop diseases are transmitted by the water, e.g., “bacterial blight of rice”.
The regular use of these pesticides may be hazardous causing poisoning. In this regard integrated pest management (IPM) favours biological control methods which are ecologically safe. The fruits and vegetables treated with biopesticides have better taste and shine.