Factors Affecting the Irrigation Requirements
The irrigation requirements depend on two factors:
1. Nature of the crop
2. Nature of the soil in which the crop is grown.
1. Nature of crop
Different crops require specific amounts of water at various stages of their growth and ripening. Some crops need more water whereas others require less water. For example, paddy crop is transplanted in standing water and requires continuous irrigation whereas others crops like wheat, gram or cotton do not require so much water.
For cereal crops like wheat, irrigation is needed before ploughing, at the time of flowering and at the time of development of grain. Irrigation of a crop at a wrong time may harm the crop resulting in the less crop yield.
For example, in case of wheat if the irrigation is done when the crop has fully matured or if, there is heavy rain at this stage then the wheat plants are unable to resist strong winds and may fall on the ground. The falling of crop in a wet field under the effect of strong winds is called lodging. Lodging adversely affects the quality and yields of both grain and the straw. In such situations; the excess water present in the field should be drained off through a proper drainage system to save the crop.
2. Nature of soil
Now let us understand how irrigation requirements depend on the nature of soil. There are two important types of soils in which the crops are grown: sandy soil and clayey soil. Sandy soil is highly porous and has high permeability that is ability to transmit water across it.
Therefore, sandy soil has very poor water retaining capacity when the crops standing in sandy soil are irrigated, the water quickly percolates down. The soil and the plants are not able to absorb adequate amounts of water. So the crops cultivated in sandy soil need more frequent irrigation. On the other hand, clayey soil has much less permeability and greater water retaining capacity than sandy soil. So when the crops grown in a clayey soil are irrigated, the plants get time to absorb sufficient quantities of water. Therefore, the crops cultivated in clayey soil need irrigation less frequently. The crops, such as paddy, which need more water, are preferably grown on clayey soils.
There are methods by which it is possible at estimate the right amount of water required for different crops sown in different types of soil.
The application of right quantity of irrigation water;
(i) ensures high efficiency of water use by the crops
(ii) reduces nutrient losses through leaching and
(iii) results in better aeration of the soil. The right amount of irrigation at the right time can help greatly in increasing our food production.