What is Olona shrub????​

Explanation:

The soil of Artic area, deserts and high mountains are weak in mineral concentration. So, the fertility of soil is poor and unsuitable for farming and cattle rearing.

So, in the Arctic area the desert and high mountain the land is highly unfavourable for practice and activities such as farming.

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theorem states that the sum of the squares of two sides of a triangle is equal to twice the square of the median on the third side plus half the square of the third side. Hence AB2 + AC 2 = 2BD 2 + 2AD 2 = 2 × (½BC)2 + 2AD2 = ½ BC2 + 2AD2 ∴ 2AB2 + 2AC 2 = BC2 + 4AD2 → (1) Similarly, we get 2AB2 + 2BC2 = AC2 + 4BE2 → (2) 2BC2 + 2AC2 = AB2 + 4CF2 → (3) Adding (1) (2) and (3), we get 4AB2 + 4BC2 + 4AC 2 = AB2 + BC2 + AC2 + 4AD2 + 4BE2 + 4CF2 3(AB2 + BC2 + AC2) = 4(AD2 + BE2 + CF2) Hence, three times the sum of squares of the sides of a triangle is equal to four times the sum of squares of the medians of the triangle.

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Explanation:

1. Afforestation:

One of the best ways to conserve soil is to increase the area under forests. Undiscriminating trees cutting should be stopped and efforts should be made to plant trees in new areas. 20 to 25 per cent, as they say, is the minimum area of forest land for the whole country which is considered healthy for soil and water conservation. Nevertheless, it was raised to 33 per cent in the second five-year plan; the proportion being 20 per cent for the plains and 60 per cent for hilly and mountainous regions.

2. Checking Overgrazing:

Grazing is very important. But overgrazing of forests and grasslands by animals, especially by herds and flocks of sheep, goats, should be properly checked. One can earmark separate grazing grounds. Alternate fodder crops should be grown in larger quantities.

3. Constructing Dams:

One of the scientific methods to check soil erosion. Soil erosion which happens maximum by river floods can be avoided by constructing dams across the rivers. Water speed can be checked and it considerably saves soil from erosion.

4. Changing Agricultural Practices:

We can save a lot of our valuable soil by bringing about certain changes in our agricultural practices. Roughly the context is described below:

(i) Crop Rotation:

As the name suggests, it is rotating crops. In India, peasants grow a particular crop in the same field year after year. This practice takes away certain elements from the soil, making it infertile and exhausted rendering it unsuitable for that crop.

(ii) Strip Cropping:

Parallel to one another, crops may be cultivated in alternate strips. Some strips may be allowed to lie fallow while in others different crops may be sown e.g., small tree crops, grains, grass legumes, etc. Numerous yields ripen at diverse times of the year and are harvested at intervals. This very method gives surety that at no time of the year the entire area is left bare or exposed.

(iii) Use of Early Maturing Varieties:

Primary budding varieties of crops take really very less time to mature. Thus putting lesser pressure on the soil. In this way it can help in reducing the soil erosion.

(iv) Contour Ploughing:

Technical methods, one can say. Ploughing is done at right angles to the hill slope, following the natural contours of the hill. It makes the ridges and furrows break the flow of water down the hill. As gullies are less, this prevents excessive soil loss. It is likely to develop and reduce run-off so that plants receive more water.

(vi) Terracing and Contour Bunding:

Claims to be one of the oldest methods of soil conservation. Terracing and contour bunding across the hill slopes are very effective. It is done by cutting hill slope into a number of terraces having horizontal top and steep slopes on the back and front.

(vii) Checking Shifting Cultivation:

Shifting cultivation method is mainly used by tribal. We can persuade tribals to switch over to settled agriculture by checking shifting cultivation. Arrangements for tribal resettlement can help to make them understand the new way of cultivation. The new method involves the provision of agricultural implements, residential accommodation.

(viii) Ploughing the Land in Right Direction:

Ploughing the land in a perpendicular direction to wind direction. This also reduces wind velocity and protects the topsoil from erosion.