Modern drip irrigation has become the most valued innovation which minimises the use of water and fertiliser by allowing water to drip slowly to the plant roots, either onto the soil surface or directly onto the root zone, through network of valves, pipes, tubings, and emitters etc.
If properly designed, installed, and managed, drip irrigation, also called trickle irrigation, conserves water by reducing evaporation and deep drainage compared to other types of irrigation since water can be precisely applied to the roots zone.
Drip irrigation is mainly adopted in areas facing acute water shortage and especially for crops such as cotton, maize, sugarcane, coconuts, grapes, bananas, citrus, straw berries, and tomatoes. Proven yield and crop quality responses to drip irrigation have been observed in onion, cauliflower, lettuce, melon and tomato etc. It is easy to install and design drip irrigation system which can reduce disease problems associated with high levels of moisture on some plants.
The efficiency of drip irrigation results from two primary factors. The first is that water soaks into the soil before it can evaporate or run off. The second is that water is only applied where it is needed (at roots).
If water conservation methods such as drip irrigation are not adopted, Balochistan will face serious water shortage by the next 15 years. Drip irrigation not only saves 40-60 per cent of water but also increases yield of crops up to 20 per cent per hectare.
Sub-surface drip irrigation (SDI) is preferred by growers. In this system drip tapes are permanently or temporarily buried at or below plant roots. It is becoming popular for row crop irrigation, especially in areas where water is scarce or recycled water is used for irrigation.
Water use can be managed efficiently with SDI without water losses due to evaporation, runoff, and only wetting the soil under the root zone. Agricultural chemicals can be used efficiently with drip irrigation. Timely application of herbicides, insecticides and fungicides are possible. Where insecticides are labeled for application through drip irrigation, less insecticide may be required to control pests. Fertiliser savings is about 95 per cent in drip irrigation system.
Other advantages of this system are that it does not need leveling of the field and has the ability to irrigate irregular-shaped fields, allowing safe use of recycled water. Moisture within the root zone can be maintained at field capacity. Soil type plays less important role in frequency of irrigation and minimises soil erosion and labour cost.
Drip is adaptable to fields with odd shapes or uneven topography. This system works well where other systems are inefficient because parts of the field have excessive infiltration, water puddling, or runoff. The system can be designed and managed so that the wheel rows are sufficiently dry so that tractor operation is possible at any time at the convenience of the growers.
Initial cost may be a bit more than overhead systems. Sunlight can affect the tubes used for drip irrigation, shortening their usable life. If water is not properly filtered and the equipment not properly maintained, it can result in clogging. Drip irrigation might be unsatisfactory if herbicides or top dressed fertilisers need sprinkler irrigation for activation.
In lighter soils subsurface drip may be unable to wet the soil surface for germination. The system requires careful consideration of the installation depth. It can also enhance weed control in arid climates by keeping much of the soil surface dry. Ultimately, there must be an economic advantage to drip irrigation to make it worthwhile. The tubes need to be saved from insects, and animals and farming tools to avoid leakages.
Various management practices are needed to get maximum benefit from drip irrigation for a longer time. Chlorine or other chemicals can be used in the drip line periodically to kill bacteria and algae. Acid might also be needed to dissolve calcium carbonates. Filters must be managed and changed as needed. The frequency of flushing depends on the amount and kinds of sedimentation in the tape. Root intrusion needs to be controlled for some crops. Rodents must be controlled, especially where drip tape is buried.
The drip tape needs to be sufficiently near the surface to germinate the seed if necessary. For example, SDI with tape tube 4-5 inches deep has been used successfully to germinate onion seeds in silt loam soil.
Drip irrigation with more water than a plant's requirement will result in the loss of most of drip irrigation benefits. The soil will be excessively wet promoting disease, weed growth and nitrate leaching. Irrigate to replace soil moisture deficit in the top 12 inches of soil.
Since only the crop root zone is irrigated, nitrogen already in the soil is less subject to leaching losses. Total nitrogen requirements are reduced using drip irrigation and less nitrogen should be applied in each application. Chemical analyses of the irrigation water and competent technical advice are needed before injecting chemical fertilisers into drip tape. Again, there is a need to improve water rotation programme to ensure timely irrigation. It happens that there is excessive availability of irrigation water when crop doesn't need it and the result is loss of water.
Growers are suggested to irrigate crops optimally because over and under-irrigation is detrimental for crop growth. To cope with water shortage, reorganisation of water sector institutions for economic utilisation of water resources, building storage structures to overcome droughts and to develop comprehensive water and hydro resource, a new policy is necessary.
The government should give priority to drip irrigation as the system conserves water significantly. The drip irrigation has great potential in our desert regions of Thal, Cholistan and Thar. Since water is a limiting factor in sandy deserts, it should not be applied by flood irrigation as most of it will percolate down the root system through sandy soils. It should be applied by drip irrigation using local PVC pipes.
A well-designed drip irrigation system or subsurface drip irrigation system will lose practically no water to runoff, deep percolation or evaporation. Irrigation scheduling can be precisely managed to meet crop demands, holding the promise of increased crop yields and quality. Growers new to drip irrigation might want to start with a relatively simple system on a small acreage.
Drip irrigation might be unsatisfactory if herbicides need sprinkler irrigation for activation. Once the zones are assigned and the drip system is designed, it is possible to schedule irrigations to meet the unique needs of the crop in each zone. Filters must be able to handle worst-case scenarios. Finally, be sure to include both injectors for chemigation and flow meters to confirm system performance. Systematically monitor the lines for physical damage.
Once a month, the drip lines may be flushed by opening the far ends of a portion of the tubes at a time and allowing high velocity water to rush out the sediment. If drip lines become plugged in spite of maintenance, many cleaning products are available through irrigation systems suppliers.
The government should prepare an efficient water conservation plan and monitor its effective implementation at the field level. Under the prevailing water scarce situation of the country, using drip irrigation is of great importance and is a do or die situation for the nation and our future generations.