Intermittent irrigation a must to curb water wastage

Surinder S Kukal and KB Singh

DIVERSIFYING area under paddy to other crops has been and is being advocated in the northwestern region of the country. Various schemes for crop diversification have not seen the light of day due to the lack of economically matching alternative crops and the absence of assured procurement at the minimum support price. On the other hand, the area under paddy has increased consistently. During the past decade and a half, the area under paddy increased from 28 to 31.7 lakh hectares in Punjab. The area irrigated by canal water declined from 16.6 lakh hectares in 1990-91 to 11.4 lakh hectares in 2020-21. This has led to grave depletion of groundwater, thereby threatening the sustainability of agriculture in the food bowl of the country. Farmers have to bear a large financial burden to deepen their tubewells for extracting water from deeper layers, thereby adding to their debt burden. The state government also has to shell out a lot of money every year to ensure subsidised power supply to the tubewells. The government subsidy on agricultural power in Punjab increased from Rs 2,805 crore in 2009-10 to Rs 7,722 crore in 2022-23.

The practice of continuous flooding of paddy fields, varying from one to three months, coupled with heavy irrigation has put great pressure on groundwater, which is falling at an average rate of 65-70 cm every year. The actual water consumed in paddy fields, in the form of evaporation and transpiration, is 650-700 mm, for which farmers consume more than 1,800 mm of irrigation water, apart from rainwater. This gap between actual crop requirement and that applied by the farmers needs to be lowered for ensuring water-efficient paddy. The intermittent irrigation after two weeks of continuous standing water, as recommended by Punjab Agricultural University long ago, is not being followed by farmers, thanks to the highly subsidised power for tubewells in the region. It is high time that a power supply policy be framed and implemented by the states so that the same amount of paddy could be grown with half the water being consumed presently.

It is well known that during very wet years (good rainfall), the paddy yields in Punjab and Haryana are lower than during the dry ones (below-normal rain). The micro-climatic conditions become conducive for a higher incidence of insect-pests and diseases. Intermittent irrigation results in better conditions for a lower incidence of pests and diseases. This lowers the input (pesticide) costs, apart from lesser extraction of groundwater. Thus, to achieve effective intermittent irrigation, it is proposed that the power supply to the feeders be provided as per the intermittent irrigation schedule. A particular feeder supplying eight hours’ power daily during the period of two weeks after the transplanting date must shift to intermittent supply at an interval of two days after the previous irrigation. But power supply should be dedicatedly ensured for 14-16 hours. This way, the state will be able to save power. The sheer wastage of irrigation water can be avoided by intermittent irrigation. Increasing the power supply duration from eight to 14-16 hours will lead to avoidance of repeat irrigation in a partially irrigated field. This power supply policy, if implemented, can prove to be a win-win situation for the farmers and the state.

Also, the power supply in the command area of a particular feeder needs to be curtailed 15 days before the expected harvest time of the paddy crop. Similarly, during rainy days, the agricultural power supply should be stopped altogether. Otherwise, even during the rains, the tubewells keep running, leading to the loss of water as well as energy.

Vital interventions

• The side-effect of laser levelling of fields, being adopted on a large scale by farmers, has led to the creation of bigger irrigation plots (more than two acres), which ideally should be less than one acre for paddy. The bigger the irrigation plot, the higher will be the application of irrigation water.
• A huge amount of irrigation water gets wasted before and during puddling. Fields are continuously filled with water 2-3 days before the actual puddling and transplanting. The fields should be irrigated just before puddling and transplanting, and the depth of standing water should not exceed 5 cm.
• Short-duration cultivars of paddy should be promoted as a shorter irrigation period leads to better water-saving.
• The transplanting of paddy should ideally begin after June 20 to escape the harsh and dry weather conditions and hence save upon water use by the crop.
• The depth of irrigation water in paddy fields during an irrigation should not be more than 5 cm as a higher depth of standing water leads to faster movement of water into the soil.
• The under-bund percolation in the paddy fields should be checked by ensuring not to remove the puddle for plastering the field bunds.
• Farmers should avoid the use of automatic starters at tubewells as they lead to unnecessary application of irrigation even if it is not actually required or it is the rainy season.
• The aerobic cultivars of paddy need to be developed for saving water both in direct-seeded and puddled transplanted cultural systems.
• Sturdy and affordable sensors like tensiometers need to be developed and standardised for the exact time of irrigation of the paddy crop, especially during uncertain weather conditions.

A blend of a well-framed agricultural power supply policy and efficient cultural practices can ensure a water-efficient paddy-wheat system. It can reduce the groundwater extraction to the extent of 40-50 per cent of what is being consumed by the traditional practice of irrigation, especially in the case of paddy. In addition, it can reduce the state’s burden on subsidy for agricultural power supply.

Kukal is a member of the Punjab Water Regulation & Development Authority, Chandigarh; KB Singh is Director, Punjab Agricultural Management & Extension Training Institute, Ludhiana