what is irrigation | factor affecting irrigation | Advantages of Irrigation

Irrigation

Crop plants get water from soil. Soil obtains water from rain. However, sufficient rain is not always available. Therefore, soil is not able to supply sufficient water to crops. The extra water required by crops is met through irrigation. The process of supplying water to crop plants by means of canals, wells, reservoirs, tube-wells, etc., is known as irrigation.

In our country, there are 12 major river basins and 8 composite river basins. Ground water also contributes significantly to our total water resources. This is replenished by rainfall. However, only 55% of our cropped area is either partly irrigated (about 25%) or is under assured irrigation (about 30%). Remaining about 45% of cropped area is unirrigated and is dependent on rain for the cultivation of crops. It is called rainfed agriculture. The success of rainfed agriculture depends upon timely and sufficient rain during most of the growing season. Scarcity and irregular distribution of rain can cause drought (sookha). Drought prone areas generally have light soil (sand-rich soil) which is unable to retain water for long.

Advantages of Irrigation

In agriculture irrigation fulfil the following goals:

1. Crop plants are irrigated with freshwater to supply two essential elements to them, hydrogen and oxygen. Both of these elements are present in water molecules and are necessary for growth and development of crop plants.

2. Irrigation of crop fields is necessary to provide sufficient moisture for the germination of seeds, as

seeds do not germinate in dry soils.

3. Irrigation of crop plants is essential for the growth and elongation of the roots of the crop plants.

This is because roots of crop plants fail to develop and elongate in dry soil.

4. Irrigation is necessary to increase the number of aerial branches (called tillers) in crop plants so as to get a good crop yield. 5. Irrigation is essential for the absorption of nutrient elements by the crop plants from the soil. The irrigation water tends to dissolve the nutrients present in the soil of a crop field to form a solution. This solution of nutrients is then absorbed by the roots of crops for the development of the plants.

Some other Advantages of Irrigation

Irrigation has many other advantages compared to natural rain water supplies.

(1) The supply of water by irrigation is regular and reliable, where as rainfall is often seasonal or unpredictable.

(2) Irrigation water supplied by rivers in flood often carries silt which adds to soil of the fields, enhancing

fertility and crop yield.

(3) With irrigation, cultivation can be done round the year and not during the rainy season only.

(4)In desert areas, the constant flow of irrigation water through the soil helps to reduce the salinity of

the soil. However, if the water is allowed to evaporate in the fields, salt content of soil will increase.

(5) Modern multipurpose dams not only provide water for irrigation but also help to control floods,

generate hydroelectric power and improve the navigability of the rivers.

Factors Controlling Irrigation

The irrigation or water requirements of crop plants depends on the following two factors:

1. Irrigation dependent on the nature of the crop plants (i.e., crop-based irrigation)

2. Irrigation dependent on the nature of soil of the crop fields (i.e., soil-based irrigation).

•  Crop-based irrigation. Water requirements of different crops are different during the various stages of their growth and maturation (ripening). Some crop plants require more water, while others need less water. For example, paddy crop (rice crop) is transplanted in standing water (wet lands) and requires continuous water supply, whereas, other crops such as wheat, gram and cotton requires less water. For cereals such as wheat, irrigation is required before ploughing the field (i.e., before tilling), at the time of flowering and at the time of development of the grain.

•   Soil based irrigation. Irrigation also depends on the nature of the soil in which crop is grown. The crops grown in a sandy soil need irrigation more frequently, whereas the frequency of irrigation is comparatively less for crops grown in a clayey soil.