How the application of scientific knowledge has made agriculture possible in arid zones, drylands, and hills?

Q.  How the application of scientific knowledge has made agriculture possible in arid zones, drylands, and hills?

A.  The advancements in our scientific knowledge have now enabled us to practice agriculture in arid zones, drylands, and hills.
 Arid Zones  - The chief arid areas of our country are confined to Rajasthan, Gujarat, Haryana, Karnataka, and Ladakh. They cover an area of about 400,000 square kilometers. Of this, Ladakh has a cold desert spread over 70,000 square kilometers.
           Here, aridity and low temperature limit the agricultural season to about five months in a year. Therefore, crops that require a short period to mature and can withstand severe cold are grown. These are some cereals, oil seeds and fodder crops. In the hot desert regions, of Rajasthan, Gujarat, and Haryana, there is an abundance of sunshine which causes high rate of evaporation. Many of these areas have adequate reserves of ground-water which is scientifically tapped for irrigation. In the arid zone fruit trees like ber and pomegranate and fuel-wood yielding trees like Acacia (Kikar), Prosopis (Mosquite) and Eucalyptus (Safeda) are grown. In such areas, large scale planting of shelter-belts minimizes soil erosion caused by wind. It also helps in the establishment of pastures and grazing lands. Later on, this land is used for growing pearlmillet and mungbean.

Dry Lands - Drylands constitute about 74% of our cultivated lands and produce about 42% of our food. These are entirely rain-dependent and crop fortunes are closely linked to the vagaries of the monsoon. Sometimes rains may set in very early or very late or may come on time but withdraw too soon. There may also be large breaks between showers. When evaporation and loss of water by seeping in the soil exceeds rainfall, these lands are plagued by drought, scarcity of drinking water and thus crop failure. Rain water is collected in ponds to support agriculture. In Dry lands with red soil, deep ploughing helps in conserving water while In black soils, sowing two crops at a time is possible with surface drainage and good water management. Leaves and crop residues, when mixed with soil improve its texture, and water holding capacity. Crops like pigeonpea and castor that have deep roots, are cultivated in these regions which improves the physical condition of the soil further, as the roots of these crops add organic matter. Varieties of sorghum, millets, sunflower, safflower, mustard, groundnut, various pulses and cotton are available which grow within a shorter time withstanding scarcity of water and also diversifying crops in dry lands. A variety of crops and cropping patterns allow the farmer to make a proper choice of what to grow in different climates and soil types.

Hills - Based on a study of the slope and depth of the soil, and availability of water, scientists have devised an interesting agricultural system that requires low inputs and puts the land to most productive use without disturbing the ecosystem. Under this system, the upper reaches of the hills are devoted to forestry. The next zone is developed for growing fruit trees, perennial fodder grass and legumes. The roots of legumes fix nitrogen and improve the soil. In the third zone, a mix of crops are raised on terraces constructed with low-cost implements. Earthen dams are constructed with locally available material. These collect enough water to be utilized for irrigation.