NCERT Solutions For Class 7 Science Chapter 9 Soil

The water holding capacity is the highest in (ii) clayey soil.

In addition to the rock particles, the soil contains (iii) minerals, organic matter, air and water.

The percolation rate is given by the following expression:

Percolation rate = amount of water (mL)/time taken(min)       

Therefore, Percolation rate = 200 mL/40min

                                            = 5 mL/min

The differences between clayey soil and sandy soil are as follows:

Clayey soil has maximum water holding capacity due to which it retains water for absorption by the plants for longer period of time. Also, clayey soil is rich in humus that provides nutrients to the plants for their growth. Thus, clayey soil is very useful for the crops.

Ways of preventing soil pollution are as follows:

1. Minimising the use of pesticides and fertilisers
2. Banning the use of polythene
3. Treating chemicals and other waste products of industries before releasing them into soil or water
4. Abandoning the practice of defecation in open

Ways of preventing soil erosion are as follows:

1. Planting of trees at large scale
2. Putting check on deforestation
3. Protecting and expanding forest covers

Following is the well-labelled sketch of the cross-section of soil and its various layers:

Soil is formed by the process of weathering. In this process, rocks are broken into smaller particles by the action of wind, water and various other climatic factors. The slow and continuous action of these factors converts massive rocks into fine particles of soil over a period of millions of years.

The correctly solved crossword puzzle is as follows:

The correctly matched contents of Column I and Column II are as follows: