New methods can halve the use of water in growing rice - the water saved can equal a fourth of all Asia’s usage.
Drought-proofing of paddy cultivation is now possible thanks to the availability of technology for growing rice the same way as wheat — that is, without keeping the fields filled with water all the time. The new know-how helps cut down water requirement of paddy by 40 to 50 per cent.
This technology has been developed under a collaborative research project of the Indian Council of Agricultural Research (ICAR) and the Philippines-based International Rice Research Institute (IRRI). The ICAR’s Cuttack-based Central Rice Research Institute (CRRI), one of the participating institutes in this project, has identified paddy varieties which can be grown like most other crops with just a few rounds of irrigation. It has also evolved a package of agronomic practices for raising these varieties to get almost the same kind of yields as those from the normally grown high-yielding paddy.
Technically called aerobic (with aeration) rice cultivation, this technique does not require the fields to be churned under stagnant water (an operation called puddling), nor does it require raising of nurseries and transplanting of seedlings in the inundated fields. The seeds are sown directly in the meticulously-levelled fields, thus saving on labour costs as well.
According to CRRI director T K Adhya, a Brazilian strain of aerobic rice, named Apo, counted among the world’s best aerobic rice strains, has been crossbred with Indian paddy strains to evolve varieties suitable for Indian agro-ecological conditions.
These varieties, using 40 per cent less water, can yield 4 to 5 tonnes of paddy under good management. Paddy grown on the uplands under aerobic conditions (without stagnant water) generally yields less than 2 tonnes a hectare.
The breeding material for evolving aerobic paddy strains, including Apo germplasm, was received from IRRI. Several promising new varieties are now being tested in the fields. One such variety, Sahabhagi Dhan, has already been notified through the IRRI-India/CRRI drought breeding network for cultivation in the drought-prone areas.
Normally, 3,000 to 5,000 litres of water is needed to produce 1 kilogramme of rice. “Such profligate use of water in irrigated paddy cultivation is unsustainable,” maintains CRRI’s crop production division head K S Rao. According IRRI’s reckoning, a 10 per cent reduction in water use for paddy irrigation, globally, can spare 150 billion cubic metres of water (equivalent to 25 per cent of all the water used in Asia) for non-agricultural use.
However, there are certain glitches in aerobic rice cultivation which need special measures to overcome them. One such problem is the abundance of weeds in the fields where the seeds are planted without flooding the soil. These weeds compete with the crop plants for consuming available plant nutrients, thus depriving the crop of adequate nutrition. This problem is especially serious in the first 30 days of crop growth. CRRI scientists recommend the application of herbicides to suppress the weeds.
The other major problem is the deficiency of iron — when there is no standing water, the presence of atmospheric oxygen oxidises the available iron in the soil, making it unavailable for the plants. This lowers crop productivity. Experts recommend addition of iron sulphate to the soil to combat this menace.
The experiments conducted on aerobic rice cultivation have revealed that the best results are obtained when the fields are ploughed and levelled with the help of laser land-levelling machines which help get a uniformly even soil surface. Also, the seeds need to be sown mechanically with the help of seed drills.
Paddy planting machines have already been evolved for dibbling the seeds in rows at the predetermined distance and depth. These can be operated with bullocks, tractors or power tillers. The mechanisation of sowing operation offers several advantages, including saving of seeds, optimum plant population per hectare, less weeding cost and, consequential higher yields.
The promotion of aerobic rice cultivation can, therefore, be a significant means of safeguarding paddy crop from the adverse impact of poor rains or inadequate availability of irrigation water.
Aerobic rice farming can be especially useful for areas under multi-cropping (where rice is grown in sequence with other crops) with underground water, as in the north-western grain bowl of Punjab, Haryana and west Uttar Pradesh and several intensively paddy-growing areas in south. Otherwise, paddy cultivation may have to be given up in such areas as the ground water is receding to inaccessible depths due to over-exploitation.