Explain the following :
i. The year 1921 is known as the 'demographic divide'.
ii. The period during the years 1951 - 1981 is often referred to as the period of 'population explosion'.
Despite tank irrigation being a simple form of irrigation, it is not used by all farmers. Explain Why.
i. Many tanks dry up during the dry seasons and fail to provide water when needed.
ii. Silting of tank need to be treated at regular intervals.
iii. Sometimes it is difficult to carry water from tank to the field for the irrigation.
i. Today the need to conserve water resources has become greater that ever. Explain.
ii. Mention two steps that need to be undertaken for the conservation of water resources.
i. What geographical conditions are required for the growth of wheat?
ii. Compare wheat cultivation in India and China - with reference to the varieties grown .