:
Explanation: 1 Mark each including figure
The different layers of soil are:
1) A-Horizon: This is the uppermost layer of the soil and is called as topsoil. The colour of this layer is the darkest since it is rich in humus and minerals.It is soft, porous and holds more water than the other layers. Plants get most of the nutrients and water from this layer.
2) B-Horizon: It is the second most layer from the top, lighter in color, may contain little humus and is rich in minerals. It serves as a water reservoir.
3) C-Horizon: It consists of small pieces of original rock broken due to weathering.
4) Bedrock: It is the bottom layer of the soil and is unweathered solid rock.

Answer: Option A. -> True
:
A
Each layer in a soil profile is called as horizon. Horizon B is found below the Horizon A layer. This layer has a lesser amount of humus but more of minerals. It is generally hard and more compact. It is also known as the middle layer.

Answer: Option B. -> i - c; ii - d; iii -a; iv - b
:
B
Wheat requires clayey soil which can hold large amounts of water.
Paddy requires clayey soil with lots of humus content.
Lentils require loamy soils which can hold an average amount of water
Cotton requires sandy-loamsto grow.

:
a) 3 Marks
b) 2 Marks
a)Soil is our most important natural resource. It is useful to us in many ways:
(i)We depend on the soil for food, clothing and shelter- By supporting growth of plants, the soil provides us with food. Much of our clothing, such as cotton and wool, can be traced to the soil. Plants also provide us with the medicines, fuel, paper and wood which is used in making furniture and for constructing houses.
(ii) We depend on the soil for minerals- Industries use the minerals dug out from the earth.to extract metals, such as iron, gold, silver and so on. These are used in thousands of industries that produce various useful things for us.
(iii) We depend on the soil for water- Water that seeps into the soil is stored underground as subsoil water. We use this water for drinking and other purposes.
b) Earthworms makeburrows in the soil. This makes the soil loose, allowing air into it and water to drain from it. Earthworm also forms channels in the soil for the root to spread through. For this reason, the earthworm is referred to as 'farmer's friend'.

:
Soil type: 1 Mark
Reason: 1 Mark
Idol makers use rich clayey soil mixed with alluvial soil.
Clayey soil retains moisture and becomes very sticky when wet. It becomes easy for the sculptors to carve out idols using this soil. Furthermore when dry,clayey soil becomes so hard that baking becomes redundant.

:
Statement: 1 Mark
Explanation: 2 Marks
This statement is absolutelycorrect.
Clayey soil has an important characteristic that it can retain water and moisture and therefore it is very useful for growing cereals like wheat, gram etc.
Sandy soils are highly porous and have very little water retention capacity. Plants require water for photosynthesis. In the absence of water in the soil, they will wilt and die.

:
Identification: 1 Mark
Justification: 2 Marks
(a) Lichens and (b) Mosses.
Lichens and mosses release substances which break down the rocksresulting in the formation of soil. The mode of action here is chemical.
Lichens grow on the surface of rocks. While growing, they release certain substances that cause the rocks to breakand form a thin layer of soil. Other small plants mosses, are able to grow on this surface now and they cause the rocks to breakfurther. The roots of big trees sometimes go into cracks in the rocks and as the roots grow bigger, the size of the cracks increase.

:
Preventing soil erosion: 1 Mark each
Soil can be conserved by following any of the methods mentioned below:
Any three:
1. Practicing no-till farming. In no-till farming, crops are allowed to remain rather than being ploughed at the end of the season. This keeps the soil tight.
2. Using terrace farming or contour farming. In this method of farming, crops are planted on steps to prevent soil from being run off with rainwater.
3. Planting rain gardens. Rain gardens are planted along slopes of a hill to keep the soil tight.
4. Using a rain barrel. Rain barrels store water instead of letting it run off, eroding soil along with it.
5. Planting windbreaks. Windbreaks or shelterbelts stop the flow of wind, preventing soil erosion by wind.
6. Restoring wetlands. This gives the water some place to go without eroding the soil in other places

:
Preventive measures: 1 Mark each
Soil erosion can be prevented by the following methods:
1. Afforestation:Afforestation means planting trees.The roots of the treeshold the soil layer firmly and prevent soilerosion.
2. Improve drainage: Areas with heavy water runoff canuse underground perforated drainage pipes which will help prevent soil erosion.
3. Contour farming and terracing: It is the practice of tilling sloped land along lines of consistent elevation in order to conserve rainwater and to reduce soil losses from surface erosion.

:
Each point: 1 Mark
(i) If particles are larger in size and cannot fit close together and have space between them, then it is sandy soil.
(ii) We know that clay can be differentiated by looking at the size of particles because they would be less than 0.075 mm in size. When water is added to a sample of soil and it turns into a sticky mass and shows great variation in volume and shows considerable strength when dried, then the soil must be clay.
(iii) If the soil sample has particulate matter larger than the previous sample and exhibits slightly plastic or a non-plastic behaviour, then the soil must be silt.
(iv) If the soil sample has even proportions of sand, silt and clay, it has to be loamy soil.
(v) If the soil is dark in colour and has dead and decaying matter, it must be humus.