BIOLOGY (class-Ix)

 

Chapter-3:               (Improvement in Food Resources)

 

Introduction

Food is the essential requirement of all living beings. Man in the early period experienced a nomadic life and hunted animals. Food is needed to perform several life activities. Thus, food is required for growth, development and body repair. It also protects the body from diseases and provide energy for doing all life functions. For example, food supplies proteins, carbohydrates, fats (lipids), vitamins, minerals and water to our body.

Humans depend on plants and animals for food

      Of all the living organisms present on earth, only green plants are Autotrophs, i.e., they make their own food. Green plants perform a basic metabolic activity, called photosynthesis, in which they use the energy of sunlight and combine carbon dioxide (CO₂) and water (H₂O) to produce carbohydrates (food). In contrast to green plants, animals and human beings are heterotrophs, i.e., they depend on plants and other animals for food. Human beings have been doing farming and rearing animals to meet their food requirements, from past immemorial times. Indeed all the parts of one or other plant, such as root, stem, leaf, flower and fruit, are consumed by humans in the form of cereals, vegetables, spices and fruits. Animals produce milk, butter, egg, meat, etc., which also supplement our food requirements. In India, to meet our food requirement, we produce about 360 million tonnes of plant products and 88 million tonnes of animal products annually.

Some Edible Crop Plants

l     Fruits. Apple, Apricot, Banana, Custard apple, Date palm, Grapes, Guava, Litchi, Mango, Mulberry, Muskmelon, Orange, Papaya, Peach, Pear, Pine apple, Pomegranate, Watermelon, Coconut.

l Seeds. Cereals: Maize, Rice, Wheat, Barley, Pearl Millet (Bajra), Sorghum (Jowar)

l     Pulses: Black gram (Urad), Pigeon pea (Arhar), Cow pea (Lobia), Gram/Chick pea (Channa), Green gram (Moong), Pea, Soyabean.

Nutrients as food for Plant

The food required by plant is composed of certain chemical elements, which are known as nutrients. Though plants absorb a large number of elements form its environment only following sixteen of these are found to be essential for the plant nutrition.

Carbon	Oxygen	Hydrogen	Nitrogen
Phosphorus	Potassium	Calcium	Magnesium
Sulphur	Iron	Manganese	Boron
Zinc	Copper	Molybdenum	Chlorine

Criteria for the essentiality of a plant nutrient

An element must fulfill the following requirements to be an essential plant nutrient:

l     In the absence of the element the plant is not able to complete its life cycle.

l     The deficiency of a particular element can be prevented or corrected only by supplying that nutrient.

l     The element must have a direct influence on the plant nutrition and metabolism.

Sources of Essential plant nutrients

There are three different sources from where a plant gets the 16 essential nutrients. These sources are air, water and soil. On the basis of these sources, essential plant nutrients are classified as follows

Air	Water	Soil
Carbon Oxygen	Hydrogen	Nitrogen, Phosphorus, Potassium, Calcium, Magnesium, Sulphur, Iron, Manganese, Boron, Zinc. Copper, Molybdenum, Chlorine.

Classification of Nutrients

Out of the above 13 soil nutrients needed for plant growth, these have been classified into two classes.

Macronutrients : The nutrients required by plants in major quantities.

l     Nitrogen

l     Phosphorus

l     Potassium

l     Calcium

l     Magnesium

l     Sulphur

Micronutrients : The nutrients required by plants in minor quantities.

l     Iron

l     Manganese

l     Boron

l     Zinc

l     Copper

l     Molybdenum

l     Chlorine

 

Manures and Fertilisers

Manures

       Manure is an organic matter used as fertilizer in agriculture. Manures are natural fertilizers. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen that is trapped by bacteria in the soil. Higher organisms then feed on the fungi and bacteria in a chain of life that comprises the soil food web.

Livestock manure is traditionally a key fertilizer in organic and sustainable soil management. It is most effectively used in combination with other sustainable practices. These include crop rotation, cover cropping, green manuring and the addition of other natural or biologically friendly fertilizers.

In organic production, manure is commonly applied to the field in either a raw (fresh or dried) or composted state.

Types

There are two classes of manures in soil management: green manures and animal manures. Compost is distinguished from manure in that it is the decomposed remnants of organic materials (which may, nevertheless, include manure).

Most animal manure is faeces — excrement (variously called “droppings” or “dung” etc) of plant-eating mammals (herbivores) and poultry — or plant material (often straw) which has been used as bedding for animals and thus is heavily contaminated with their faeces and urine.

Green manures are crops grown for the express purpose of plowing them under. In so doing, fertility is increased through the nutrients and organic matter that are returned to the soil. Leguminous crops, such as clover, also “fix” nitrogen through rhizobia bacteria in specialized nodes in the root structure, This further contributes to the fertility of the soil by feeding the fungi in the soil.

Other types of plant matter used as manure or fertiliser include: the contents of the rumens of slaughtered ruminants, spent hops left over from making beer.

Uses of manure

Manure has been used for centuries as a fertilizer for farming, as it is rich in nitrogen and other nutrients which facilitate the growth of plants. Liquid manure from pig/hog operations is usually knifed (injected) directly into the soil to reduce the unpleasant odors. Manure , hogs and cattle is spread on fields using a Manure spreader. Due to the relatively lower level of proteins in grasses, which herbivores eat, cattle manure has a milder smell than the dung of carnivores — for example, elephant dung is practically odorless. However, due to the quantity of manure applied to fields, odor can be a problem in some agricultural regions. Poultry droppings are harmful to plants when fresh but after a period of composting are valuable fertilizers.

The dried manure of animals has been used as fuel throughout history. Dried manure of camels and other animals (usually known as dung) was, and in some places still is, an important fuel source in treeless regions such as deserts.

Farmyard Manure (FYM)

This is the decomposed mixture of cattle excreta (dung) and urine along with the litter (bedding material used at night under cattle) and left-over organic matter such as roughage or fodder. This material is collected daily from the cattle shed and stored in a pit for decomposition by the microbes.

 

Compost

Compost is prepared from farm and town refuge such as vegetable and animal refuse (e.g.,  excreta of domestic animals such as cattle, goat, sheep, horse, donkey, camel, dogs, cats. etc.), faecal matter of human beings, sewage waste weeds, crop stubble, straw, rice, hulls, forest litter, etc. Composting  is a biological process in which both aerobic (organisms requiring the presence of oxygen for the respiration) and anaerobic (organisms, in which respiration takes place in the absence of oxygen) microorganisms decompose the organic matter. It takes about 3 to 6 months for decomposition of organic refuse.

Table
Approximate NPK Values of Various Animal Manures

Animal	% nitrogen	% phosphoric acid	% potash
Dairy cow	0.57	0.23	0.62
Horse	0.70	0.25	0.77
Sheep/goat	1.44	0.50	1.21
Rabbit	2.40	1.40	0.60
Chicken	1.00	0.80	0.39

       Fertilizers are compounds given to plants with the intention of promoting growth; they are usually applied either via the soil, for uptake by plant roots, or by foliar spraying, for uptake through leaves. Fertilizers can be organic (composed of organic matter, i.e. carbon based), or inorganic (containing simple, inorganic chemicals). They can be naturally-occurring compounds such as peat or mineral deposits, or manufactured through natural processes (such as composting) or chemical processes (such as the Haber process).

Fertilizers typically provide, in varying proportions, the three major plant nutrients (nitrogen, phosphorus, and potassium), the secondary plant nutrients (calcium, sulphur, magnesium), and sometimes trace elements (or micronutrients) with a role in plant nutrition: boron, manganese, iron, zinc, copper and molybdenum.

Inorganic fertilizers (Mineral Fertilizer)

l     Examples of naturally-occurring inorganic fertilizers include sodium nitrate, mined “rock phosphate” and limestone (a calcium source, but mostly used to reduce soil acidity).

l     Examples of manufactured or chemically-synthesized inorganic fertilizers include ammonium nitrate, potassium sulphate, and superphosphate, or triple superphosphate.

l     Synthesized materials are also called artificial fertilizers, and may be described as straight, where the product predominantly contains the three primary ingredients of nitrogen (N), phosphorus (P) and potassium/potash (K), which are known as NPK fertilizers or compound fertilizers when elements are mixed intentionally. They are named or labelled according to the content of these three elements, thus a 5-10-5 fertilizer would have 10 percent phosphate in its ingredients. If nitrogen is the main element, they are often described as nitrogen fertilizers.

Nitrogen fertilizer is often synthesized using the Haber-Bosch process, which produces ammonia. This ammonia is applied directly to the soil or used to produce other compounds, notably ammonium nitrate, a dry, concentrated product.

Organic fertilizers

l     Examples of naturally occurring organic fertilizers include manure and slurry, urine, peat, seaweed and guano. Green manure crops are also grown to add nutrients to the soil. Naturally occurring minerals such as mine rock phosphate, sulphate of potash and limestone are also considered Organic Fertilizers.

l     Examples of manufactured organic fertilizers include compost, dried blood, bone meal and seaweed extracts. Other examples are natural enzyme digested proteins and fish meal.

Important roles played by the organic components and humus of soil

l     Mobilizing existing soil nutrients, so that good growth is achieved with lower nutrient densities while wasting less

l     Releasing nutrients at a slower, more consistent rate, helping to avoid a boom-and-bust pattern

l     Helping to retain soil moisture, reducing the stress due to temporary moisture stress

l     Improving the soil structure

l     The possibility of “burning” plants with the concentrated chemicals (i.e. an over supply of some nutrients)

l     The necessity of reapplying artificial fertilizers regularly (and perhaps in increasing quantities) to maintain fertility

l     The cost (substantial and rising in recent years) and resulting lack of independence

Organic fertilizers also have their disadvantages:

l     As acknowledged above, they are typically a dilute source of nutrients compared to inorganic fertilizers, and where significant amounts of nutrients are required for profitable yields, very large amounts of organic fertilisers must be applied. This results in prohibitive transportation and application costs, especially where the agriculture is practiced a long distance from the source of the organic fertilizer.

l     The composition of organic fertilizers tends to be highly variable, so that accurate application of nutrients to match plant production is difficult. Hence, large-scale agriculture tends to rely on inorganic fertilizers while organic fertilizers are cost-effective on small-scale horticultural or domestic gardens.

l     Finally, some organic fertilizers such as manures can contain bacteria or heavy metals harmful to human health, leading to a risk of the produce being contaminated and harmful to humans, or bearing disease.

In practice a compromise between the use of artificial and organic fertilizers is common, typically by using inorganic fertilizers supplemented with the application of organics that are readily available such as the return of crop residues or the application of manure.

Bio-fertilizers

Bio-fertilizers are the preparations containing live or latent cells of efficient strains of nitrogen fixing, phosphate solubilizing or cellulolytic micro-organisms used for application to seed or composting areas with the objective of increasing the numbers of such micro-organisms and accelerating those microbial processes which augment the availability of nutrients that can be easily assimilated by plants. Bio-fertilizers harness atmospheric nitrogen with the help of specialized micro-organisms which may be free living in soil or symbiotic with plants. ‘Microbial inoculants’ are carrier based preparations containing beneficial micro-organisms in a viable state, intended for seed or soil application, designed to improve soil fertility and help plant growth by increasing the number of desired micro-organisms in plant.

Organic Phosphorus Sources

Organic phosphate fertilizers have been used for centuries as the phosphate source for crops. Even with the advent of phosphate fertilizer technology processes, organic phosphate sources from animal manures—including composts—and sewage sludge are still very important. From a fertilizer/nutrient management perspective, the major differentiating factor is the availability of phosphate As with any of the fertilizer products, especially those with varying analysis, chemical analysis should be done on these products. Then an availability coefficient should be used to determine the available phosphate as a portion of the reported total phosphate.

WATER

Earth’s water is always in movement, and the water cycle, also known as the hydrological cycle, describes the continuous movement of water on, above, and below the surface of the Earth. Since the water cycle is truly a “cycle,” there is no beginning or end. Water can change states among liquid, vapor, and ice at various places in the water cycle, with these processes happening in the blink of an eye and over millions of years.

 

Figure 7. 1 Water Cycle

Properties of Water

l     Water is called the “universal solvent” because it dissolves more substances than any other liquid. This means that wherever water goes, either through the ground or through our bodies, it takes along valuable chemicals, minerals, and nutrients.

l     Pure water has a neutral pH of 7, which is neither acidic nor basic.

l     Water is unique in that it is the only natural substance that is found in all three states – liquid, solid (ice), and gas (steam) – at the temperatures normally found on Earth. Earth’s water is constantly interacting, changing, and in movement.

l     Water freezes at 32^o Fahrenheit (F) and boils at 212^o F (at sea level, but 186.4^° at 14,000 feet). In fact, water’s freezing and boiling points are the baseline with which temperature is measured: 0^o on the Celsius scale is water’s freezing point, and 100^o is water’s boiling point. Water is unusual in that the solid form, ice, is less dense than the liquid form, which is why ice floats.

l     Water has a high specific heat index. This means that water can absorb a lot of heat before it begins to get hot. This is why water is valuable to industries and in your car’s radiator as a coolant. The high specific heat index of water also helps regulate the rate at which air changes temperature, which is why the temperature change between seasons is gradual rather than sudden, especially near the oceans.

l     Water has a very high surface tension. In other words, water is sticky and elastic, and tends to clump together in drops rather than spread out in a thin film. Surface tension is responsible for capillary action, which allows water (and its dissolved substances) to move through the roots of plants and through the tiny blood vessels in our bodies.

l     Today, global desalination capacity is approaching 10 cubic kilometres a year—roughly 3 per cent of the global domestic tap water supply. Two thirds of this is devoted to processing seawater and the rest to cleaning up brackish underground water. But water for homes is a minor demand in most countries (Britain is an exception here). Two thirds of the world’s water is used for irrigating crops. So desalinated water accounts for only a tenth of 1 per cent of total water use.

Four fifths of the world’s desalination capacity still comprises distillation works, and most of it is in the Gulf. The Saudi capital, Riyadh, which has virtually no rain and no rivers or surface lakes, alone accounts for one tenth of world output of desalinated water. In 2004, the Saudis announced plans for six more plants, costing $5bn in total.

But desalination technology is spreading fast to countries with shrinking rivers and soaring demand. Holiday islands where tourists have overwhelmed local supplies have been in the forefront. Malta now gets two thirds of its drinking water from desalination.

Judicious use of water

       India has enormous surface water resource. There are 12 major river basins and 8 composite river basins in our country. Ground water also contributes significantly to total water resources of India.

       The efficiency of existing irrigation system and the water applied in the field can be increased by its judicious use. The following methods should be adopted

l      Selection of right crop and cropping

l      Application of optimum quantity of water at correct time;

l      Keeping of weeds under controls

l      Time table based operation and

l      Pest control.

Irrigation System

       Our country is awarded with large water and land resources with varied climatic conditions. Under such circumstances, various types of irrigation systems have been adopted to supply water to the agricultural lands. Some most commonly used irrigation systems are the following:

 

Canal system

       In canal system the human-made canals receive water from one or two reservoirs or from rivers. This is usually an elaborate and extensive irrigation system. Thus, main canal is distributed into branch canals and branch canals further have distributaries or field channels.

Tanks

       Tanks are small storage reservoirs, which catch and store the runoff of smaller catchment area.

Wells

       Wells are constructed wherever exploitable ground water is present. Wells are of two types.

       Dug wells : In the dug wells, the water is collected from water bearing strata. These dug wells have their bottom below the ground water table.

       Tube wells : A tube well can tap water from the deeper strata. From these wells, water is lifted by diesel or electricity run pumps.

Need for Irrigation

Irrigation is an artificial application of water to the soil for the following purposes

• Irrigation is needed for normal growth and yield of the plant.
• It is needed for metabolic processes of the plant.
• To reduce the soil temperature.
• For easy germination of the seeds from the soil.
• Irrigation water acts as a medium for transport of nutrients and photosynthates in the plant system.
• To provide crop insurance against short duration drought.
• To washout dilute salts in the soil.
• To reduce the hazard of soil piping.

Quantum of Water Required by Plants

• Water requirement of a crop is the quantity of water needed for normal growth, development and yield and may be supplied by precipitation or by irrigation or by both. Water is needed mainly to meet the demands of evaporation, transpiration and metabolic needs of the plants. The water requirement of any crop is dependent upon :
• Crop factors like variety, growth stage, duration, plant population and growing season.
• Soil factors like texture, structure, depth and topography.
• Climatic factors like temperature, relative humidity and wind velocity.
• Crop management practices like tillage, fertilization, weeding etc.,

Quantum of Water Requirement (mm) of Different Crops Crop Water Requirement(mm) Rice 900 – 2500 Wheat 450 – 650 Sunflower 350 – 500 Castor 500 Bean 300-500 Cabbage 380-500 Banana 1200-2200 Citrus 900-1200

Crop Protection

There are various methods by which insects and diseases can be controlled. One of the most common and effective methods is the use of pesticides or biocides which include insecticides (for killing the insects), weedicides (for killing the weeds) and fungicides (for killing the fungi). Thus, chemicals (poisons) used to kill pests, e.g., weeds, insects, mites, rodents and fungi are called pesticides. These chemicals (i.e., pesticides) are sprayed on crop plants or used for treating seeds and soil.

Weeds, especially the invasive ones, due to their greater adaptability are very successful and grow at the cost of other vegetation.

Scientific Storage of Grains

During storage damage of grains can take place by following two main types of factors:

       Biotic factor : such as insects, rodents, birds, mites and bacteria.

       Abiotic factors : such as moisture content and temperature.

For the large scale storage of grains, the grain silos are used. The silos are big and tall cylindrical structures. They store stocks of food items at different levels. Silos are provided with outlets at different levels to withdraw the desired stock of grains. They have built in arrangement for aeration, temperature-control protection from insects, rats, birds and mammals. Fumigation and inspection of its grain stocks is done periodically.

Figure 7. 2 Grain Storage Silo

Control measures against pests attacking stored grains

       The grains, which are meant for human or animals consumption, should be exposed to sun or fumigated. For them, mixing of insecticide is not proper. However, seeds should be treated with insecticides for avoiding any chance of their insect infestation. Following techniques of chemical control are used for checking pest infestation of stored produce.

       Chemical control by spraying of insecticides : Spraying of gammaxene or BHC, Pyrethrum and Malathion at 3 weeks interval may be done for the treatment of the surface area of the store house (Godown or warehouse).

       Fumigation: Fumes means vapour or gas. In fumigation method the insecticide solution is converted into fumes to kill the insects.

Sustainable Agriculture

Conventional agriculture is often considered unsustainable for two reasons:

(1)    Reliance on non-renewable resources, and

(2)   Concern that some practices may cause long-term damage to soil, such as erosion from excessive tillage. Organic farming is a promising alternative, but most organic food production currently uses both fossil fuels (for tractors) and tillage. Hydrogen made by electrolysis, using electricity from solar cells or windmills, may someday replace fossil fuels most farmers use to power tractors and the natural gas used in the manufacture of synthetic nitrogen fertilizer but this will invariably introduce other problems. Reducing erosion and restoring the human-nature relationship are research priorities for both conventional and organic systems.

MIXED FARMING

Systems, the largest category of livestock system in the world, cover about 2.5 billion hectares of land, of which 1.1 billion hectares are arable rainfed crop land, 0.2 billion hectares are irrigated crop land and 1.2 billion hectares are grassland. Mixed farming systems produce 92% of the world’s milk supply, all buffalo meat and approximately 70% of the sheep and goat meat.

In many tropical areas the main constraint to increased output of livestock products is the inability of producers to feed animals adequately throughout the year. Yet opportunities exist to enhance ruminant livestock feed supplies by using crop residues, such as cereal straw and legume haulms. Greater emphasis is therefore now being placed on vegetative production in plant breeding research. Crop residues also play an important role in conserving soil moisture, preventing erosion and providing products such as fuel or thatch for smallholders.

Mixed Cropping

Mixed cropping is the practice of growing of two or more crops simultaneously on the same piece of land. In India the following combinations of the crops are used by farmers in mixed cropping :

Soyabean + Pigeon pea

Maize + Urad bean

Cotton + Mung bean

Groundnut + Sunflower

Wheat + Chick pea

Wheat + Mustard.

Poultry in India

Poultry is one of the fastest growing segments of the agricultural sector in India today. While the production of agricultural crops has been rising at a rate of 1.5 to 2 percent per annum, that of eggs and broilers has been rising at a rate of 8 to 10 percent per annum. As a result, India is now the world’s fifth largest egg producer and the eighteenth largest producer of broilers. Driving this expansion are a combination of factors – growth in per capita income, a growing urban population and falling real poultry prices.

The history of poultry in India is some 5000 years old. Although the most contemporary Breeds in western countries were developed from Red Jungle and Silver jungle fowls which originated in India but the credit for pioneering action for poultry development in India should be given to a few Christian Missionary Organizations and some British People who brought some superior exotic breeds in the beginning of the 20th century.

Although India still accounts for a very small share in poultry production and consumption world-wide, the Indian poultry industry has been growing at a rate of 15- 20% during recent decades – faster than any other meat sector in the country.

Eggs and broiler meat are the major end products of the poultry sector in India. Presently production of eggs is estimated to number about 37 billion, that of broilers 895 million, and that of poultry meat 735,000 tonnes. The value of egg and poultry production in India during 1980-2000. In addition, organized facilities have been set up over the years for the manufacture of egg powder and frozen, processed broiler meat essentially to cater to export markets and markets in the metropolitan areas of India.

Indian Fisheries

Catla Catla

This is the fastest growing carp in India. The adult fish and advanced fingerlings are distinguished by deep body with a conspicuous head, large upturned mouth, non-fringed lips, devoid of barbels and a broad dorsal fin with 14 to 16 branched rays. The body is ordinarily dull, silver white, but tends to be rather darkish in weedy waters.

Catla is reported to grow very quick, even 7.5 to 10 cm.per month. In normally stocked waters a growth of 37 to 45 cm.in the first year can ordinarily be expected. Catla grows to over 1.5 metre in length. The fish in the second year attain sexual maturity and are ready to breed in the third season after hatching.

Labeo rohita (Rohu)

Rohu is considered tastiest of the Indian carps. It is easily distinguished by its relatively small or pointed head, almost terminal mouth with fringed lower lip, dull reddish scales on the sides and pink reddish fins. The dorsal fin has 12 to 13 branched rays. The body is more linear than that of Catla.

Rohu grows quickly, though relatively slower than catla. A growth of 35 to 40 cm. can normally be expected in the first year in a well stocked pond. Sexual maturity is attained towards the end of the second year. Rohu grows to over 1 metre in length.

Cirrhina Mrigala (Mrigal)

Next in importance to catla and rohu for cultural purpose is the mrigal. It is easily distinguished by the relatively linear body, small head with rather blunt snout, terminal mouth with thin nonfringed lips, bright silvery body and reddish fins. The dorsal fin has 12 to 13 branched rays.

Mrigal grows slower than catla or rohu. The species attains a maximum length of over 0.75 metre. It becomes sexually mature in the second year.

Labeo Calbasu (Calbasu)

The species is suitable for cultivation in confined waters. Body oblong, moderately compressed. Width of head equal to its length without snout. Mouth narrow obtuse; lips thick and fringed, each with a distinct inner fold. Two pairs of barbels. Origin of dorsal fin mid way between snout and base of caudal, which is deeply forked. Colour of the body slate black, scales sometimes with a scarlet centre, eyes red in colour. Maximum length about 90 cm.

 

Cyprinus Carpio (Common Carp)

The common carp (Bankok strain) has been found to adapt to these warm waters and grow satisfactorily. It reaches sexual maturity on attaining 35 to 40 cm. in length and 1 to 1.5 kg. weight in the first year of its life. The fish unlike Indian major carps breed in ponds almost throughout the year with a peak period from January to April.

Macrobrachium malcomsonii (Freshwater Prawn)

It is the second biggest fresh water prawn. 9-11 teeth on dorsal rostrum, straight, project beyond antennular peduncle and 5-7 teeth in ventral side of rostrum. Spines not sharp, closely arranged. Grows up to 20 cm. and the male grows faster than female. Omnivorous in feeding habits with occasional cannibalistic tendency. Breed easily in captivity and berried females were observed at 40-50 mm.size.Fecundity.3400 to 68,000.

 

ASSIGNMENT

Very Short Answer Questions

1. Define a weed.
2. Name two fertilizers.
3. Name one insecticide.
4. Define vermicomposting.
5. Write expanded form of EDCT.

Short Answer Questions

1. Write names of essential micronutrients of crop plants.
2. Define mixed cropping.
3. What are pesticides? Name one pesticide.
4. Name the factors responsible for grain loss during storage of grain.
5. Differentiate between manure and fertilizers.

Long Answer Questions

1. Why do we irrigate our crops? Explain.
2. Describe various measures for controlling insect pests and diseases in crops?