Essay on Irrigation: Necessity, Principles and Methods

After reading this essay you will learn about:- 1. Necessity for Irrigation 2. Problems of Irrigation Farming 3. Principles 4. Methods.

Essay on the Necessity for Irrigation:

Indian agriculture is severely handicapped by the erratic distribution of rainfall in different seasons. It not only varies from one region to another but, also from year to year in the same region.

If irrigation water is available during the period of rapid growth of crops and their flowering and grain formation stages, the yields of crops and the resultant money returns from them could can be maximized by efficient utilisation of all the agricultural resources.

Vegetable farming is not possible without irrigation. The tremendous increase in agricultural production in India can only be attributed to the judicious use of irrigation water, fertilizers and high yielding varieties during the last two decades.

Essay on the Problems of Irrigation Farming:

Some well waters especially in Uttar Pradesh, Haryana and Rajasthan—are saline, and their applications to land has made lands saline and have dissolved the salts in the superficial layer of the soil profile, which have moved upwards along with the upward movement of water in the dry season to accumulate on the surface of the lands. Water seeping out of the irrigation canals have elevated the ground water at many places in Uttar Pradesh and Haryana.

Essay on the Principles of Irrigation:

The amount of irrigation water and its frequency of application depend on compensating the water deficit in the root zone just before the crop wilts with sufficient excess water to wash down the accumulated salt if any into the drains.

Wilting coefficient of soils varies from about three per cent in coarse sandy soils to about twenty per cent in fine clayey soils, whereas the field capacity ranges from about eight per cent in coarse sandy soils to about forty per cent in fine clayey soils.

Only that much water should be applied to fields which in necessary to raise the soil moisture content at root zone of the concerned crop to the field capacity level. Water should not be wasted by applying too much to the field as this will unnecessarily leach down the plant nutrients from the root zone.

Usually about 0.5, 1.0, 2.0, 2.5 and 3.0 acre inches of water are required to wet sandy soils, sandy loam soils, loam soils clayey loam soils and clayey soils respectively to a depth of one foot.

Since the moisture retention capacity of soils increases when their texture become finer, so the soils of finer textures and those of coarser textures may be irrigated at an approximate interval of seven days and ten days respectively under average conditions. A handful of the soil of the concerned field is manipulated in the hand in an attempt to make a ball.

The field should be irrigated if the soil exhibits the following characteristics:

(i) The sandy loam soil will not form the ball. It will become lighter in colour when it is dried.

(ii) The loamy soil will form the ball which will break down when it is tossed upwards again caught in the hand.

(iii) The clayey soil will form the ball which will crack open when it is squeezed.

The appearance of the standing crop may also indicate whether or not it needs irrigation. The field should be irrigated when the largest leaves of the crop wilt in the midafternoon, or it turns unusually dark green in colour. The concerned field should continue to be irrigated till a blunt stick can easily be pushed to a depth of one foot and thereafter it should be stopped.

Most of the crops grow best and produce maximum yield if the soil moisture content is maintained at the field capacity level at least during the period of rapid vegetative growth, flowering and grain and fruit formation stages.

A high moisture level helps to develop succulence and softness in vegetable and fodder crops. Young plants should be more frequently irrigated than at later stages because their root system have not developed deep enough to utilize the moisture from the deeper layer of the soil.

Essay on the Method of Irrigation:

Methods of irrigation may be grouped as follows:

1. Surface Irrigation:

Flood irrigation:

Irrigation water is let in the field usually at one side of the field, so that it can flow freely in all directions. Some portions of the field may be over irrigated while other portions may be under irrigated. Some portion of the field may be water-logged.

Bed Irrigation:

Small beds are made on the levelled field. The beds are surrounded by low 6 to 12 inches high earthen embankments or bunds. Two rows of beds are irrigated from one sub-channel that runs between the rows. Bed irrigation is usually practiced for some vegetables growing on any soil except sandy soils.

Basin Irrigation:

Small circular basins are made around fruit trees. A small circular area around the stump of the fruit free is kept dry be erecting small bunds of 6 to 9 inches height. Water is supplied to each basin and the sub channels that connect the basins to the main irrigation channel. Basin irrigation is suitable for soils of any texture. It makes the most efficient use of irrigation water.

Furrow Irrigation:

Crops are grown on ridges that have been made on levelled land and water is applied in furrows on either side of the row of crop on the ridge, One-sub channel is made at one side of the field for supplying water to the furrows.

2. Sub-Surface Irrigation:

If any impervious layer exists below the root zone, then ditches are dug up to the impervious layer. Water is applied to the ditches when it moves laterally and vertically to wet the root zone. If no impervious layer occurs below the root zone then porous or perforated pipes are laid there for supplying water to the root zone of the crop.

3. Sprinkler Irrigation:

The water is sprayed to the crop from overhead pipes which comprise of the main line and the laterals. The main pipes are usually made up or iron or steel. Aluminum lateral pipes are usually portable, and are fitted with riser pipes, which in turn are fitted with sprinkler nozzles each of which applies water to a circular area of a diameter that depends upon the size of the nozzle and the pressure of the water.

The rate of water application varies from one fourth to three-fourth inches per hour. This is controlled by using nozzles of a proper size and water pressure in the laterals and the discharge of individual sprinklers are controlled by valves that have been fitted with the pipe lines.