Accumulation of salts in the Root Zone

In conventional methods of irrigation, the percolating or leaching water, which is going waste, takes away the accumulated salts in the top layer and reduces the salt content of the top layer of the soil.

In drip irrigation system, water is used to wet the shallow root zone only. All the losses of water through percolation and seepage will be arrested. The salts that are present in the irrigation water will be left in the top layer of the soil as the water is lost through evapotranspiration only. As a result, all the salts that are present in the irrigation water will be accumulated in top layer of the soil and create salinity hazard in the long run.

However, in drip irrigation system, the effect of salinity does not visualize early, as the soil is kept at higher level of available moisture (field capacity) status throughout the crop growth period due to which the salt concentration is reduced. Whenever dry spell prevails or watering through drip system is stopped, the crop plants may suffer from salt injury in the fields where drip system is followed for longer period of time.

Drip irrigation provides both water and essential plant nutrients (through fertigation) at the shallow depth of the soil, the root zone of the plant confined to the shallow depth of the soil. In contrast, in the conventional irrigation methods, the plant extracts water and nutrients from deeper layers of the soil and the root zone of the plants gets extended to the deeper layers of the soil in search of water and nutrients. Whenever cyclone or Gale/passes through the crop fields, there will be a possibility of lodging of crop which is fed through drip irrigation system. This envisages the susceptibility of the crop plant fed through drip irrigation system to the lodging due to shallow root system.

Establishment of the drip system needs all the components to life the water, filter the water and distribute the water, irrespective of the extent of the area. Majority of the dry land farmers are having small holdings with poor resource base. The high initial investment hinders the farmer to opt for drip irrigation system.

Mechanical damage to the plastic laterals/drippers by rodents is a problem and needs attention to control the rats.

The small openings of drippers will be clogged by soil particles, organic matter, algal particles or chemical precipitants etc. Hence frequent cleaning of drippers is necessary.

The clogged particles can be removed by flushing of filters, laterals, mains and drippers periodically. Injection of acids (HCI & H2SO4) into the drip system controls clogging due to chemical precipitation and biological particles. Acid treatments are required when Ca and Mg content in the irrigation water exceeds 50 ppm.

The laterals spread in the field for delivering water near plant surface obstructing the field operations like inter cultivation operations aimed to control weeds and conserve moisture.

In light or sandy soils, where the lateral movement of the water is very less and downward movement or vertical movement is very high, too many number of drippers are required to cover the field which is not desirable.

Despite the demerits of drip irrigation, it is gaining momentum year after year. Nearly, 4.5 lakh ha was under drip irrigation system in India during 2002-2003. Among the states, Maharashtra is first in the rate with

1.2 lakh ha.

Though there are several advantages with the drip irrigation system, in majority of states, the percentage of farmers adopting drop irrigation has decreased soon after removal of subsidy. This confirms the high initial investment and inability of farmers in establishing drip irrigation system due to their poor resource base. Hence, the governmental and non governmental organizations should encourage the farmers in adopting the highly efficient system of irrigation by providing subsidy.

In drip irrigation system, water will be used more efficiently, and there will be saving in irrigation water to the extent of 40-60 per cent. The saved irrigation water due to the adoption of drip irrigation system can be used to extend the area under irrigation. The productivity of the farm will grow and will be sustained due to increase in area under irrigation, reduced weed growth, reduced pest and disease incidence. Similarly, the profitability of the farming enterprise will also be increased due to increased productivity as well as reduced input costs like fertilizer.

Though the establishment of the drip system is expensive, the increase in productivity will pay back the cost of establishment of the drip irrigation system in a period of 4 to 5 years. Thus there is tremendous scope for drip irrigation system in enhancing and sustaining the productivity of the farm as a whole in rainfed and limited irrigated regions.

 
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