FARMERS, since the early days of agriculture, are aware of the importance of irrigation in crop production. Thousands of years ago, the settlers of Sindh and Baluchistan constructed barrages on Sindh, Saraswati and other rivers to irrigate their dry crop fields. But little improvement was made in the irrigation system until the steam engine was invented.
In Bangladesh, mechanical irrigation system started in mid 1950s with the introduction of power pump. It was used to irrigate rice fields by basin method. Later, groundwater and canal irrigation systems were developed. However, efficiency (Water Use Efficiency, WUE) of this method is rather low (between 30 and 40 per cent). That is because, in this process known as surface irrigation method, a lot of water is wasted (conveyance loss) during its passage from the source to the field to be irrigated.
In Bangladesh, drip irrigation is a new method in which water is applied to the root zone in drops. Its concept is to create a continuous wetted strip along the lines of the plants. It increases the efficiency of both water and fertilizer use to a great extent.
Worldwide acreage under drip and micro-sprinklers has increased (annual anticipated increase between 6 and 12 per cent) tremendously in recent years. In most cases, fruits and vegetables are irrigated by these irrigation methods. WUEs of these methods are 80 to 90 per cent. Higher water and fertilizer use efficiencies contribute to quicker return on investment.
Study findings from different research institutions in India have shown that in the drip irrigation method from 30 to 70 per cent water is saved. The study further showed that if the fertigation method is used, yields of crops like tomatoes, potatoes, carrots, cucumbers, watermelons and strawberries turns out to be almost double of that produced through traditional fertilization. Fertigation is the application of fertilizer and irrigation water together to plants and trees.
In Bangladesh, traditionally flood or border irrigation method is used for fruit and vegetable cultivation. But it adversely affects soil health and crop production as water is not used judiciously. A study was undertaken at the Bangladesh Agricultural Research Institute (BARI) to investigate the performance of drip fertigation on tomato crop in terms of its technical and economic feasibility.
In the study, different doses of nitrogen fertilizer were compared with traditional furrow irrigation method. Used oil drums of 215-litre capacity were placed at 1.5 metres height supported by a bamboo structure. Water from drums was carried to each plant through mainline, sub-mainline and micro-tubes. These tubes are prepared from rubber hose pipes made locally. At the end of each micro-tube was connected a dripper.
Results of the experiment reveal that the yield in drip fertigation (85 t/ha) was 38 per cent more than that produced through furrow irrigation (62 t/ha). Nitrogen requirement was only 100 kg/ha against 250 kg/ha in furrow method. Water applied in drip fertigation was only 224 mm compared to 416 mm in furrow method. The gross margin in drip method was Tk 306,000/ha against Tk 249,000/ha in furrow method. Labour used in drip was 20 per cent less than that in the furrow method.
It can thus be concluded that drip fertigation is technically suitable and economically viable in Bangladesh. It saved 60 per cent urea and 46 per cent water. Other high value crops like brinjal (aubergine), papaya, banana, guava, lemon, orange etc. can be grown profitably by drip fertigation. The method is especially suitable in the salinity-affected and hilly areas. Extension programme should be undertaken to popularize this modern and very profitable technology among farmers and entrepreneurs in different areas of the country.