BIO(Soil Pollution)

                 Soil Pollution

         Our living Planet, consists of

Atmosphere, Earth and Water. The

interaction of the Atmosphere,

Lithosphere, Hydrosphere and Biosphere

is continuing for years together. It was

clean and enjoyable. But due to the various

activities of man, the composition and

complex nature of environment got

changed. The activities include

industrialization, construction,

transportation, agriculture and

deforestation etc.., Such activities are

though desirable for human development

and welfare release unwanted materials into

the environment causing it to be imbalanced

rendering our life miserable.

What is soil?

Air, water and soil are three major

natural resources, alongside soil is one of

the marvellous products of nature without

which there would be no life. It is a natural

medium for plants to grow.

Soil is made up of minerals and

decomposed organic matter, along with air

and water. Soil is a habitat for many

organisms like, bacteria etc.., which in turn

feed and support plant life.

Healthy soil means the soil which

produces healthy plants, on eating which

animals also remain healthy.

How is soil formed?

Soil formation is a long and complex

process and it can take 100 to 10,000 years

to create one inch of top soil! It is driven

by many factors such as Climate,

Topography, living organisms and the type

of parent material. Parent materials come

from break down of underlying rocks or

from deposits by streams and rivers, seas

and gulfs, hills, wind and glaciers or organic

plant residues.

Over time, these materials are

weathered by the effects of freezing,

thawing, wetting, drying, heating, cooling,

erosion, plants, animals and from chemical

reactions. Eventually the parent material is

divided into three horizontal layers, the top

layer consists of mostly organic matter and

biological activity, the middle layer is the

zone of maximum material accumulation

and the bottom layer is mainly the parent

material.

The top soil is important since it is the

foundation for the life on the earth.

Soil properties:

Crop quality directly depends on

the quality of the agricultural soil in which

it is grown. The higher the quality of the

soil, the higher the quality of the crop

produced. To improve how to obtain high

quality soil, we must first understand the

fundamental properties of soil. These can

be divided into three major categories 

physical, chemical and biological

properties.

Physical properties of soil:

Soil comprises of minerals, organic

matter, water and air. The composition and

proportion of these components greatly

influences physical properties of soil

including colour texture, structure and

porosity. These properties regulate and

affect air and water movement in the soil

and thus, soil ability to function. Organic

matter is the organic component of soil

which includes the dead and decaying

plants, animals and residues of organisms.

It consists of nutrients necessary for

plants growth such as Nitrogen, Phosphorus

and Potassium. Soils which contain 30%

or more organic matter are considered

organic soil; all other soils are identified

as mineral soils. Organic matter in soil

improves water infiltration, decreases

evaporation, and increases the water

holding capacity. Also, where there is

organic matter, there will be numerous

organisms present helping to convert it

back to nutrients and these organisms help

to create crumb, ideal for cultivation. Thus

balancing a natural state of soil.

Chemical properties of soil:

The term pH is used to indicate the level

of acidity or alkalinity of a soil. The range

of pH values of a good soil lies from 5.5

to 7.5. Below pH 7 the soils are termed as

acidic and above pH 7 alkaline.

The pH of soil is important to know the

type of vegetation that grows in the soil and

the type of organisms that live there. Also,

presence of organic matter in soil has a

close relationship with soil pH. Soil richer

in organic matter is acidic in nature as a

result of degradation of various substances

that produces various acids in soil.

Availability of plants nutrients depends on

the pH of soil.

Biological properties of Soil:

Soil is not a dead mass but an abode of

millions of organisms. It is the most

abundant and diverse ecosystem on the

earth. Soil organisms include both plants

and animal forms ranging from sub

microscopic Viruses to Earthworms, to

large burrowing animals such as Gophers

and ground Squirrels. Major microbial

groups in soil are bacteria, fungi, algae and

protozoa. These feed on plant residues

burrow the soil and help in aeration and

percolation of water.

This is the basis of nutrient cycles in all major ecosystems of the world. Besides their role in controlling the rates of production of inorganic forms from various organic forms, soil microbes, particularly, soil bacteria also control the forms of ions in which these nutrients occurs. We shall study this in detail in the chapter of ‘Biogeochemical cycles’.

SOIL FERTILITY:

How can you say that soil is fertile one. Discuss with your classmate write your opinion.

Fertility of soil depends on the properties of soil and is defined by its capacity to hold

water and nutrients and supply them to plants when they need them, independent of direct

application of nutrients. Transfer of nutrients from the soil’s organic matter to the mineral

stage strongly depends on the soil organisms’ activity and diversity. Soil organisms also

contribute to buildup soil organic matter, including Humus, the soil’s most important nutrient reservoir.

Proper soil fertility management is

very important for successful crop

production and farming. Organic farmers

regulate soil fertility by protecting the soil

and feeding it organic material, thus

ensuring quality yield. When the soil is

fertile in the organic sense, it can produce

good crop yields for several years. You

learned about organic farming in the

chapter 'Challenges in improving

agriculture.

Soil Pollution:

As we discussed above, soil serves as

the interface between Earth, Air and Water;

fulfilling a variety of complex,

interdependent functions essential to life.

Yet human activities alter its ability to

perform its job. As compared to the other

resources, it has taken a long time to

become aware of the wealth, complexity,

usefulness and fragility of the Soil. When

the quality of Air and Water deteriorates,

the threat to public health is felt

immediately. But as long as we can walk

on the earth under our feet, where’s the

danger?

The impacts of various human

activities for development and welfare are

invisible and land pollution is a good

example of that. We can’t easily see the

poisons that seep from underground

Mines, the Garbage we have dip into

landfills or from Industrialization,

Agriculture and other mismanagement by

human being. Land pollution, in short, is a

much bigger and more subtle problem than

it might appear. How does it occur? And

what can we do about it? These are the

questions to think about. But first let us

understand up to what extent we are as

human being, responsible for producing this

waste.

Let us read the following conversation

and prepare the list as per the instructions.

During interval time Venu was eating a

fruit. He was about to throw the peel in

corner of the varandah. His friend Ramu

stopped him. Ramu said you should not

throw waste in the varandah. Drop it in the

bin / basket.

Now let us think, what will happen if

you throw the wastes where ever you want?

Prepare a list of waste materials we

throw out in a day from morning to evening

classifying them as wet wastes and dry

wastes with the help of the example given

in the table below.

Activity-1:

Dumping and decomposing

We are producing tonns of wastes in

our daily activities. It is dumped at

wherever the vacant place is available in

Urban as well as Rural areas. Some of these

Can you imagine the quantity of waste we produce in a day and what happens to the waste materials we throw or dispose?

Activity-2:

Take a polythene bag/plastic bucket /

or any container. Fill half of it with soil.

Keep wet waste and other wastes in it.

(Waste should include vegetable peels,

rubber, plastic etc). Add some more soil

and sprinkle water regularly on it. Till it and

observe in 15 days intervals. 

The waste generated from various

sources can be categorized into two types:

i) Biodegradable waste includes

substances that can be degraded by

microbes into harmless and non-toxic

substances.Agricultural and animal wastes

like leaves, twigs, hay, dung, etc. are

biodegradable wastes

Decomposition is the process of

degradation of materials into simpler

substances turning them into nutrients and

making available to plants.Thus, biodegradable materials contribute directly to

the fertility of the soil. However when there

is an excess of bio-degradable material, it

contributes the imbalance in the nature with

negative impact. On the other hand, nonbiodegradable materials directly contribute

to land pollution due to the excessive

amount and improper waste management.

Thus, soil or land pollution can be

understood as addition of substances which

adversely affect the quality of soil or its

fertility. Farmers use cow dung every year

in the fields. Polluted water also polluts

soil. Solid waste is a mixture of plastics,

cloth, glass, metal, organic matter, sewage,

sewage sludge, building debris, generated

from households etc.., commercial and

industrial establishments add to Soil

Pollution. Fly ash, iron and steel slag,

medical and industrial wastes disposed on

land are important sources of soil pollution.

In addition, fertilizers and pesticides from

agricultural use which reach soil as run-off

as well as land filling by municipal

waste are growing causes of soil pollution.

Acid rain and dry deposition of pollutants

on land surface also contribute to soil

pollution.

ii) Non-biodegradable waste cannot be

easily degraded. Aluminium cans, plastics,

glass, chemicals like DDT, etc. are

examples of non-biodegradable wastes.

Radioactive wastes produced during

nuclear reactions take a long time to decay

and are harmful to human beings. Now -adays 'e-waste' (computers, mobile waste)

also leads to soil pollution.

Causes of land pollution:

There are many different ways by which

land pollution can occur. Soils are

commonly used as dumps for household

and industrial wastes. In many intensively

farmed areas, leaching of nutrients from

manure or inorganic fertilizers and

effluents from processing plants may lead

to high level of nitrate and other chemicals

in ground water. Due to atmospheric

deposition (air pollution) soil gets

contaminated significantly. soil pollution

can be classified into the following

categories based on sources:

Agricultural Soil Pollution

Soil pollution by industrial

effluents and solid wastes

Pollution due to urban activities

Soil pollution is caused by the

presence of man-made chemicals or other

alteration in the natural soil environment.

This type of contamination typically arises

from the rupture of underground storage

links, application of pesticides, and

percolation of contaminated surface water

to subsurface strata, oil and fuel dumping.

Biomagnification:

The nutrients necessary for plant growth

(e.g., Nitrogen and Phosphorus) are found

at very low concentrations in most natural

waters. In order to obtain sufficient

quantities for growth, Phytoplankton must

collect these chemical elements from a

relatively large volume of water.

In the process of collecting nutrients,

phytoplankton also collects certain humanmade chemicals, such as some persistent pesticides.

 Bio magnification

Deforestation:

Soil Erosion occurs when the

weathered soil particles are dislodged and

carried away by wind or water.

Deforestation, agricultural land

development, temperature extremes,

precipitation including acid rain, and human

activities contribute to this erosion.

Humans speed up this process by

construction, mining, cutting of timber,

over cropping and overgrazing. It results in

floods and soil erosion.

Forests and grasslands are an excellent

binding material that keeps the soil intact

and healthy. They support many habitats and

ecosystems, which provide innumerable

feeding pathways or food chains to all

species. Their loss would threaten food

chains and the survival of many species.

During the past few years quite a lot of vast

green land has been converted into deserts.

Deforestation is slowly destroying the most

productive flora and fauna areas in the

world, which also form vast tracts of a very

valuable sink for Co2.

 Deforestation

Pollution due to urbanization:

Pollution of surface soils

Urban activities generate large

quantities of city wastes including several

Biodegradable materials (like

vegetables, animal wastes, papers,

wooden pieces, carcasses, plant twigs,

leaves, cloth wastes as well as

sweepings) and many nonbiodegradable materials (such as plastic

bags, plastic bottles, plastic wastes,

glass bottles, glass pieces, stone /

cement pieces). On a rough estimate

Indian cities are producing solid city

wastes to the tune of 50,000 - 80,000

metric tonns every day. If left

uncollected and decomposed, they are a

cause of several problems such as:

Clogging of drains: Causing

serious drainage problems

including the burst / leakage of

drainage lines leading to health

problems.

Barrier to movement of water:

Solid wastes have seriously

damaged the normal movement of

water thus creating problem of

inundation, damage to foundation

of buildings as well as public health

hazards.

Foul smell: Generated by dumping

the wastes at a place.

Increased microbial activities:

Microbial decomposition of

organic wastes generate large

quantities of methane besides many

chemicals to pollute the soil and

water flowing on its surface

As solid wastes and hospital wastes

create many health problems: They

may have dangerous pathogen

besides dangerous medicines, injections.

Solid waste management:

The solid wastes which are accumulated

on the soil will pose a great problem to us.

Throwing the wastes in dump yards is not

the solution to the problem. For throwing

wastes we need enormous land area.

For example in the state of Telangana

32 towns are there The average per capita solid wastes

produced per day is 364 grams. To dispose

all the wastes we need an area equal to the

size of Hyderabad city(590 sq km) by the

year 2021.

Thus, Proper methods should be

adopted for management of solid waste

disposal. Solid waste management involves

activities including collection, transfer and

transport to suitable sites, and safe disposal

of wastes by methods which are

environmentally compatible.

Industrial wastes can be treated

physically, chemically and biologically

until they are less hazardous. Acidic and

alkaline wastes should be first neutralized;

the insoluble material if biodegradable

should be allowed to degrade under

controlled conditions before being

disposed.

BIO(Ecosystems)

                   Ecosystems

         Let us discuss these questions

What is a habitat?

Is a tree habitat only for a crow?

In what way an ecosystem is different

from habitat?

We found that there were differences

between the ecosystems of land and water

and different ecosystems on land and water

as well. We can see differences within

ecosystems in very small areas as well.

We have studied in the chapter 'habitat' about 

the variations in the living

communities, as well as organisms

present at different levels, in the pond

ecosystem and the tree. In this chapter we

will see how organisms have started

inhabiting certain areas, what needs they

have and how they acquire different

conditions from their surroundings to meet

them.

                   Mangroves

To adjust themselves to diverse and

distinct changes in ecosystems, organisms

have to adapt different means for better

survival. For example, some trees such as

Mangroves like Avicennia have evolved a

curious way to deal with the problems of

growing in a wet and salty place. They have

evolved to have curious looking

These “knees” (aerial roots) develop

from the lateral roots that are growing near

the surface, and protrude up to 12 inches

out of the soil or sediment. The precise

function of these “knees” is not definitely

known, but there is general agreement that

they aid the plants in maintaining adequate

root respiration in a watery environment.

We do not find such structures in plants

growing around us.

All such ways and means that organisms

adopt or develop over a certain period of

time in different conditions for better

survival are adaptations of organisms. We

may also say that adaptation is a feature that

is common in any population because it

provides some improvements for better

survival.

Activity-1:

Take a  Aloevera and a

Balsam plant in two separate pots. Water

each of them with two tablespoons of water.

Do not water them for a week. Observe

the condition of the plants after a week.

Which plant showed growth?

Which plant dried first? Why?

Activity-2:

Collect an aquatic plant out of a water

body( Eg. Duck weed, Hydrilla, Vallisneria

etc. either floating at the surface or

propping out of it). Carry it back home and

plant it in a pot and water it.

What do you observe? Compare

your observation with that of

activity1 and write a note on what

you find.

From the above activity we see that

some plants dry up without water very

quickly, while others can grow even with

very little water. Each of these plants are

adapted to the conditions in their

surroundings on the basis of need of water.

What is meant by adaptations?

Describe your opinion.

Organisms in nature create adaptable

situations around them on the basis of their

needs. They also adapt to situations

specifically. For example in Opuntia, the

leaves are reduced to spines so that

transpiration loss is checked and water is

stored in the tissues of the stem (succulent

stems). This helps the plant to live in

conditions of water scarcity as we come

across, in deserts. Aloe vera are found in

our surroundings these days as well but you

may have heard that they are generally called

as desert plants (xerophytes).

                Opuntia

                  Baobab

                 Cactus

Though these are called Living stones they are not stones. The

swollen leaves are adapted to desert conditions, minimizing water

loss and storingwater. These are also called Pebble Plants . Each pebble is actually a leaf with a cut window that lets in light. The stone like appearance deceives the animals and saves it from being eaten. Now a days, many Xerophytes aregrown as ornamental plants in pots at homes. Some plants as a whole seem to be flowers. Some with thorns, some have flowers with bright colour petals. Now a

days these kind of plants are used as gifts for Birthdays and other occasions also.

     

             Pebble plant

Adaptations in some more desert animals

The Side-Winder adder snake crawls

sideways with only a small amount of its

body pressed against the hot sand. This

technique helps it to keep itself cool. The

Golden Mole escapes the heat of the sun

by swimming through the sand just below

the surface. It rarely emerges out as it finds

all the needs below the ground

Some animals show extraordinary

ability to survive in the desert. The

Kangaroo Rat of western North American

desert can live without drinking water

through out its life. Because its body

synthesizes little water in the process of

digestion. The desert bird the Sand grouse

flies long distances to an oasis in search

of water, which it carries back in its crop

for its nestlings.

The furry soles of Fennec Fox helps it

walk on hot sand and loses heat through its

ears. When the sand becomes too hot the

sand diving lizard holds its feet in the air to

cool down.

            Rattle snake

              Sandgrouse

 

Adaptations in Aquatic ecosystems:

We shall study two different types of

ecosystems in water (aquatic ecosystems)

and some conditions in the environment that

influence adaptations.

Aquatic ecosystems are mainly

classified into two different types as Fresh

water and Marine ecosystems.

Ponds, Lakes, Rivers are the examples

of Fresh water Ecosystems

Seas, Oceans are the examples of

Marine Ecosystems

As the living conditions are different

we come across various adaptations in

several organisms living in these ecosystems.

General aquatic adaptation as can be

seen structurally (in body structure) are

like presence of some special air spaces

inside bodies or presence of such

substances that help organisms to swim and

float in water to inhabit different levels in

the water body, or bear specialized

structures to swim like flippers as in Turtles

and fins in fishes. Fishes, Dolphins etc have

floaters in their body (special structures of

their digestive canals) to be able to inhabit

particular levels in the water body.

Microscopic photosynthetic organisms

like planktons have droplets of oil in their

cells that keeps them float. Larger plants 

have long tough leaves and flexible stems.

Marine ecosystem:

Over the last 2,000 million years, plant

and animal life on earth has continuously

evolved from its simple beginnings in the

oceans to the complex existence on land

today. It is no accident that protoplasm, a

substance found in every living cell,

strongly resembles seawater. Although

some animals emerged from the sea

millions of years ago to fill all available

places on land, some remained in the ocean

and evolved and adapted to life beneath the

surface.

The ocean covers a larger part of the

planet, yet it remains a little understood

place as scientists have limited scope for

the study of habitats that lack physical

boundaries and a span of thousands of

miles.

Adaptations on the basis of light

penetration:

Euphotic zone

The organisms living in this zone are

mostly floaters and swimmers. Animals in

this zone usually have shiny bodies

reflecting light away to merge with shiny

water surface are transparent. These usually

have very sharp vision. Plants are mostly

green and photosynthetic activity is

maximum in this zone. Some flora and

fauna of this zone are trouts, herrings,

dolphins, jelly fishes, different type of coral

colonies which are extremely colourful,

different types of algae & sea grasses

(emergent plant species: rooted to the

sides, in marine ecosystems these are

rooted in the continental shelf area)

diatoms etc. Nearly 80% of marine flora

and fauna are found in this zone.

        Coral colonies

Bathyal zone:

Most of the plants found in this zone

are the red and brown kelps, sponges, corals

even animals with tubular bodies like

squids and large animals like whales etc.

Some of these have a flat body like the ray

fishes. They may have big eyes sensitive to

very dim light

                Ray fish

Abyssal zone:

These zones are

dark and cold

throughout the year.

Photosynthetic activity

is absent. Deep sea

animals are mostly

predators and

scavengers. The larger

forms have wide

mouths and huge curved teeth which prevent

escape of any prey. Absence of skeleton,

flattened bodies are some other

characteristics observed. Some also have

special structures that produce light on their

bellies, around their eyes(which are usually

nonfunctional that is, the organisms are

blind) and at the sides of their bodies, some

animals glow (shows bio luminiscence) in

the darkness of deep waters

              Angular fish

               Brittle Star

Freshwater Ecosystems:

Fresh water ecosystems are stagnant water types as well as running water types. They may vary in size from as small as a puddle and pond to a large lake, river etc. Just like the marine ecosystems, to

study environmental conditions in lakes, some zones are marked. The Littoral zone, Limnetic zone and Profundal zones on the

basis of light penetration. Based on availability of light different kinds of organisms are found in these zones. Different factors like light, salt content, food, oxygen affect the organisms and their

populations in different ways.

Littoral zone: The shallow zone near

the shore is also called as littoral zone. The

water near the shore is usually muddy or

turbid. This topmost and warmest zone at

the edge of a water body is home to Snails,

Clams, Insects, several Crustaceans, Fishes

and Amphibians and the eggs and larvae of

Dragonflies etc.

Several organisms in this zone have

well developed sight, usually have dull and

greyish bodies and are fast swimmers.

Plants like Mosses, Water lily, Vallisneria,

Hydrilla etc are found here along with

several types of algae. High photosynthetic

activity occurs in this zone. Predators of

this zone are Tortoise, Snakes and Ducks.

The limnetic zone is the open water

zone at the top of the water body and

consequently receives a good deal of light.

This zone contains a variety of freshwater

fish with bright shiny, greyish or silver

black scales that help them to merge with

the surroundings. Transparent or whitish

bodied crustaceans like Daphnia, Cyclops,

small Shrimps are also found in this zone.

There are different types of floating plants

like Water hyacinth, Wolffia, Pistia along

with a variety of algae. 

The profundal zone is dimly lit and

cold. Mostly heterotrophs (saprochytes -

microbes that decompose dead organisms)

are found in this region. Most of the

animals, the so called bottom dwellers, that

live here are mostly scavengers and

predators, for example Crustaceans, Crabs,

Fishes like Eels and Glossogobius (isika

dondu), Snails, Turtles etc. They adapt

themselves by feeding on dead animals that

settle down. Many kinds of bacteria

(detritus) thrive here that help in

decomposing the dead organisms. Mud of

the bottom floor, tiny particles of dead and

decaying matter of plants and animal bodies

make the water very turbid. Hence the

bottom dwellers , rely mostly on smell and

auditory (related to hearing) senses rather

than vision to aquire their food.

Adaptations in some aquatic plants

Partially submerged plants have

numerous air spaces inside the stems

,leaves ,roots that aid in gaseous exchange

and buoyancy. Leaf bases of Water Hyacinth

(Eichhornia crassipes) form air filled

structures to keep them afloat. In water

lilies leaves are flat, have an oily surface

with stomata present on the upper surface

of the leaf, while incompletely submerged

plants like Hydrilla, stomata are absent,

leaves are thin, stems are highly flexible.

The main adaptations that give Hydrilla an

advantage over other native plants are: it

can grow at low light intensities, it is better

at absorbing carbon dioxide from the water

(diffuses into leaves), it is able to store

nutrients for later use, it can tolerate a wide

range of water quality conditions for

example salinity(can grow in saline waters

as well), and it can propagate sexually and

asexually.

Other examples of adaptations

Adaptation to temperature in plants

The effect of temperature on plants of terrestrial ecosystem can be seen in different ways. Do all plants shed their leaves at

same time in a year throughout the world. Some plants in

temperate regions shed their leaves before the winter starts. This is to minimize transpiration loss as well as reduce photosynthetic and other metabolic activities, as low temperature renders several chemicals inactive for some time. In tropical regions some plants

shed their leaves before the start of summer. Plants growing in hot climates, usually keep the stomata closed during the day to reduce transpiration loss. High temperatures also lead to adaptations like reduced leaf. Let us recall why xerophytic plants have modified stems and leaves.

          Adaptive Radiation in Galapagos Finches

Try to guess if there is any relation between type of food taken and the structure of beak. The seed eaters had thick and heavy

beaks. The fruit eaters had stubby beaks. The insect eaters had sharp and long beaks. . Darwin observed that these birds had adapted to their immediate surrounding for food and shelter and showed a lot of

variation even within the same species, especially with respect to the form of beaks. He made a sketch of the same as shown in the above. Thus he concluded that adaptation was something that an organism is undergoing continuously, even within very closely related forms in a particularly geographically separated area.

BIO(Agricultural Production)

                   Agricultural Production

                 

        How to increase the food

production?

        We know that the cultivated land is very limited. If we make use of plenty of land for cultivation some forests may be destroyed. This leads to environmental problems. So we need to think of another

solution. Observe the following solutions.

1. Increasing the area of cultivated land.

2. Increasing production in the existing

land.

3. Developing high yielding varieties.

4. Crop rotation

5. Cultivating Mixed crops.

6. Cultivating short term crops like Rabi.

       Which of the above option do you think

is more meaningful?

You have already learnt about long term

and short term crops or Kharif and Rabi

crops in your classes. Short term varieties

produce grains more than long term

varieties.

Alternating of crops preserve the soil

fertility. Mixed crop system helps the

farmers to produce variety of crops as well

as increase in the production.

To get high yield 3 types of methods

are being used.

1. Developing high yielding varieties.

2. Using high yield management methods.

(Crop production management)

3. Crop protection management.

Improving high yielding crop varieties:

Observe the size and colour of maize in your kitchen. (if not, ask your mother why she doesnot purchase maize as a food material) Some seeds are small with yellow colour and some are large with white colour. The white coloured large ones are hybrid variety. They give high yield. Refer annexure for more information.

   

High yielding crop management methods:

(A) Irrigation:

An experiment was conducted to find out how irrigation affected the production of a crop. In the experiment, crops were grown in two fields. One field was irrigated while the other wasn’t. The same amount of nutrients, like nitrogen, was applied to both the fields.

What does a plant do with water?

We learned in the chapter ‘Nutrition in

plants’  that a plant absorbs water 

from the soil. What does it do with this

water? We know that the plant combines

water and carbon dioxide with the help of

sunlight to produce carbohydrates. Starch

is one such carbohydrate. Different types

of sugars and cellulose are also

carbohydrates. A chemical analysis will

show that 100 grams of water reacts with

260 grams of carbon dioxide to form 180

grams of carbohydrates.

But the plant roots do not use all the

water they absorb to produce

carbohydrates. Actually, most of this water evaporates into the air.

  Activity:

Take a polythene bag. Cover the bag on

leaves and tie it. Keep it 4-5 hours. You

observe it. What did you find in the

polythene bag? Where did they come from?

Do this experiment during day time and

night time separately. Note the differences

in your note book

If you tie a plastic bag over a leaf, you

will be able to see how much water a plant

releases into the air. It is estimated that a

plant uses only 0.1 percent of the water it

absorbs to form carbohydrate.

Water evaporates through these stomata.

We know that more water evaporates when

the weather is hot. In such a situation, the

stomata begin to close. This lessens the

amount of water that evaporates from the

leaves

We learned in the chapter ‘Nutrition in

Plants’ of that plants absorb

carbon dioxide. The carbon dioxide also

enters the leaves through the stomata.

When the weather is hot and the stomata

close, what effect would this have on

the absorption of carbon dioxide by the

plant?

What effect would a change in the

amount of carbon dioxide absorbed

have on the growth of the plant?

If the plant does not get water at this

time, what effect would this have on its

growth? Discuss in your class and find

out reasons.

Plants cannot absorb nutrients directly

from soil. Only the nutrient that dissolves

in water is absorbed by the roots of the

plant. We discussed about transportation of

substances in the chapter, “Transportation

of material across the cell membrane” and

in the chapter “Plant Cell”. Try to think of

how xylem and phloem are useful in

transportation.

Water is essential for Agriculture.

What are the main water sources in your

village for agriculture? How farmers

utilize them?

Paddy require more quantity of water.

Can you give such examples?

Cultivation of paddy, wheat and sugar cane

are suitable where places have rich water

resources. If we cultivate such crops by

irrigating them with water from wells and

bore wells what will happen?

Most of the farmers of our state

cultivate crops like paddy, sugar cane

irrespective of proper availability of water,

only because of supporting price and

marketing facility. So farmers invest more

on irrigation of water, electricity bills,

pesticides and fertilizers. Agriculture

Officers advise to cultivate dry land crops

(Aruthadi Pantalu) in less water areas and

follow different water management

practices.

Make a list of crops which require

less amount of water.

Drip irrigation is a good practice in

agriculture to prevent water wastage. In drip

irrigation, water is supplied through small

pipes. These pipes have small holes through

which water passes drop by drop.

 Soil Nutrients:

Nutrients present in the soil are

consumed by plants and are replenished or

returned to the soil in many different ways.

In nature the continuous process of death

and decay add nutrients to the soil and the

process is too slow to be commercially

useful. Rotating crops, adding organic

manure or chemical fertilizers etc. are man

made processes.

Crop rotation:

Usually, farmers do not grow only one

crop in a field. Different crops are grown

in different seasons. It has been seen that

cereal crops take a lot of nutrients from

the soil. Legumes are different. While they

do take nutrients from the soil, they also

provide some nutrients to it. Growing

leguminous crops result in an increase in

the quantity of nitrogenous salts in the soil.

Thus to grow a leguminous crop between

cereal crops is beneficial either by

crop rotation or by mixed cropping.

Nitrogen, Phosphorus and Potassium

are the important nutrients.

To avoid nutrient deficiency in the soil, farmers cultivate alternate crops. A farmer cultivated sugar cane in his land for the last five years. Another farmer cultivated sugarcane in the first year and soya bean in the second year and sugarcane in third year. In which case do you think has the land lost most of its nutrients? Crop rotation is the process in which one crop is followed by another crop on an

agricultural field. Some best combinations for crop rotation are given below. After cultivation of paddy, pulses/ groundnut has to be grown, followed by paddy again for cycle to continue. After cultivation of tobacco, mirchi has to be grown for the cycle to go on.

After cultivation of redgram, maize/ paddy has to be grown for the cycle to go on.

What is the benefit of crop rotation?

When cereals are cultivated more

nutrients are utilized. If legumes are grown

in the soil, less nutrients are utilized. Not

only this, they synthesize some nutrients

into the soil. Do you find any crop rotation

methods in your village? What are they?

Ask your village elders and collect the

information about it.

Cultivating mixed crops:

Have you ever seen two types of crops

in the same field?

Which crops are grown in this way?

What are the uses of cultivating mixed

crops?

Discuss in groups and display your

writings in your classroom.

If more than one crop is cultivated in

the same field then it is called mixed crop.

Because of mixed crop cultivation, the soil

becomes fertile. The nutrients which are

used by one crop will be regained by

cultivating another crop.

Which crops can be cultivated as mixed

crops? Observe the following...

Soya grown along with Pea

Pea grown along with Green gram

Corn grown along with Black gram

Groundnut grown along with Sunflower

Groundnut grown along with Red gram

Sorghum grown along with Pea.

         Haldi Plantation

                    Red Gram

      

 

      Peanuts and groundnuts

Is betel a mixed crop?

How can you justify your answer?
Can you name some leguminous crops?
Leguminous crops usually have many small
nodules on their roots. Several different
kinds of bacteria live in these nodules.
These bacteria absorb nitrogen from the air
and convert it into a form that can be used
by the plant. You will learn more about
nitrogen fixation in Bio-Geo-chemical
cycles.
Ask your teacher about names of the
nitrogen fixing bacteria.
You could uproot a Soya bean plant or
a Bengal gram plant to see the nodules on
their roots.

Root nodules in legume plants:

The microorganisms in the nodules use

some of the nitrogen for their own purpose.

Some nitrogen is used by the leguminous

plant itself. But after the crop is harvested,

the roots remain in the soil. So the soil gets

some nitrogen in this way.

Experiments have shown that a

leguminous crop gives about 50 kg to 150

kg of nitrogen per hectare. The crop grown

after the leguminous crop can take

advantage of the availability of more

nitrogen in the soil.

Nowadays a bacterial culture is also

available. This is mixed with the seeds.

When the seeds are sown, the plants are able

to produce more nodules on their roots.

Apart from this, there are various kinds

of blue-green algae that add nitrogen to the

soil. Blue-green algae culture is also

available. It is applied in rice fields.

So if a leguminous crop is rotated with

a cereal crop, the leguminous crop

replenishes, to some extent, the nitrogen

taken from the soil by the cereal crop. But

Potassium, Phosphorus and other nutrient

elements cannot be replenished in this way.

Organic manure:

Do you ever saw a herd of goats in a

vacant field? Why shepherds make

arrangements to stay their goats and sheeps

in the field.

The organic (natural) manure is

produced by decaying the plant and animal

wastes! The manure produced from

decomposed plant and animal products has

more organic material. This gives good

nutrients to the soil. It makes the soil

fertile. Because of humus, the natural

manure, water holding capacity of soil is

increases.

Natural organic manures are generally

divided into two types. One is Concentrated

organic manures and the other is Macro

organic manure.

Groundnut, Gingelly, Castor, Coconut,

Neem, Jatropa seed powders are the

examples of Concentrated organic

manures. These are also used as fodder for

cattle and poultry.

Animal excreta, compost, deep litter

are the examples of Macro organic manure.

Nutrients are rich in the concentrated

organic manures than in macro organic

manure.

         Green Manure

Soil testing:

How do farmers know what type of

crop needs to be cultivated? What types

of crops are suitable for the soil in their

fields? Farmers, who are experienced, are

able to make out from the colour and

texture of the soil.

You had also studied about the same in

your earlier class. Ask a farmer to find

out about crops that can be grown in

different types of soil.

Nowadays, Agricultural officer and the

Soil Testing Technologist are available in

every area. They observe the field and

suggest what to do.

Have you ever heard about Soil Testing Centre?

At these centers the soil technologist collect soil samples from fields and tests the fertility levels of soil. They give us knowledge about the soil. The testing centers are situated in division and district levels. If you send the sample of soil from your field, they send you a report after testing it.

Organic farming:

By using chemical fertilizers, we can

get high yield for only 20 to 30 years. After

that soil becomes reluctant to plant growth.

These chemicals damage soil fertility. If

the soil health is proper, then only the soil

responds to fertilizers. Otherwise, usage

of fertilizers become mere waste.

Long term high yielding capacity of

soil (soil productivity) depends on both

availability of nutrients in the soil (soil

fertility) and suitable physical, chemical

and biological characters of soil (soil

health).