Sub surface method of irrigation

In sub surface method of irrigation, water is applied below the ground surface by maintaining an artificial water table at some depth depending upon the soil texture and the depth of the plant roots.

Water reaches the plant roots through open ditches or underline pipelines called tile drains or mole drains. The water application system consists of field supply channels or trenches suitably spaced to cover the field adequately and drainage ditches for the disposal of excess water.

Merits

i) High water use efficiency.

ii) Needs least labour.

iii) Low evaporation loss through ground surface.

Demerits

i) Very expensive

ii) A slight negligence in applying water may lead to water logging in root zone

iii) Water having a high salt contain cannot be used.

C) Drip irrigation method

Drip irrigation is also called trickle irrigation. It is the method of applying water drop by drop to the individual plant with a volume of water approaching the consumption use of plant by minimizing conventional losses such as percolation, runoff and soil water evaporation. In this method irrigation is done by small diameter plastic lateral lines with drippers at desire spacing. This system applies water slowly to the soil moisture with the desired range of plant growth. This method of irrigation is generally used in row crops in orchard.

Merits

1. Drip irrigation method can achieve a 90% or more application efficiency, which can hardly be achieved by any other methods of irrigation.
2. The method reduces salt concentration in the root zone when irrigated with poor ground water.
3. Soluble fertilizers and pesticides can also be applied through this method of irrigation.

Demerits

1. High initial cost
2. The requirement that the water must be relatively clear, otherwise clogging problems may occur.
3. Poor water distribution efficiency when a low pressure system is installed on steep slopes or uneven land.

D) Sprinkler irrigation method

It is also called overhead system of irrigation as water is made to spray through nozzle fitted in the stand of water conveying pipe over the foliage of the crop plants as artificial rain. Pressure is generated by pumps and IC engine and water is sprayed through orifice or nozzle. This method is used for all crops in any soil condition except in the soils having very low infiltration capacity. This method is categorized under:

a) Rotating head system

b) Perforated system.

Merits

i) Better method for ground having uneven topography or land leveling ins not essential for sprinkler irrigation.

ii) Better for light textured soils.

iii) Soluble fertilizer, insecticides and herbicides can also be sprayed easily through this system.

iv) It is detachable and portable and can be carried at any location and may be shifted to other locations after the irrigation is over.

v) Sprinkler irrigation can be used for almost all crops (except rice and jute)

vi) Small streams of irrigation can be used efficiently.

vii) Sprinkler method of irrigation can be used to protect crops against frost and high temperatures that reduce the quantity and quality of the produce.

viii) Labour costs are usually less than for surface methods on soils having high infiltration rate and on steep and rolling land.

ix) No wastage of land for bunds and ridges.

x) The irrigation method does not interfere with the movement of farm machinery.

Demerits

i) Sprinkler irrigation is 2-2.5 times costlier than surface irrigation for the same depth of water application.

ii) If the wind velocity is greater than 6 km per hour drift losses increases or evaporation losses is increases and wind distort sprinkler pattern and causes uneven distribution of water also.

iii) Clay soils that have a slow intake rate coupled with hot, dry windy areas are not suitable for sprinkler irrigation.

iv) Sprinkling water may cause fungal disease, wash pollen and reduce fruit set.

v) If the water containing large quantity of dissolved salts, this method may not be useful.

vi) Power requirement is high.