The suitable areas include irrigated lowlands, where rainfall is insufficient to sustain rice production.
Present day conventional method of rice cultivation utilises 5,000 litres of water for producing one kg of rice than its actual requirement of 3,000 litres. About 2,000 litres is lost due to flooding and seepage losses. Further, decline in water table necessitates the need for improved water-use efficiency and water productivity in agriculture, particularly in rice cultivation.
Thus, the newly upcoming approach of rice cultivation called aerobic rice cultivation reduces water use in rice production and increases the water use efficiency. In simple words, growing rice plant as irrigated crop like cultivating maize and wheat in aerobic condition, where oxygen is plenty in soil.
The suitable areas for aerobic rice cultivation includes irrigated lowlands, where rainfall is insufficient to sustain rice production, delta regions where there is delay in water release from reservoir, irrigated system of rice cultivation, where pumping from deep bore well has become so expensive and favourable upland system has access to supplementary irrigation.
Accordingly, Tamil Nadu, Jharkhand, Chhattisgarh, parts of Bihar, Odisha, Karnataka, and eastern Uttar Pradesh are the projected area where there is uneven distribution and frequent occurrence of soil moisture limitation.
In aerobic rice cultivation, rice is cultivated as direct sown in non-puddle aerobic soil under supplementary irrigation and fertiliser with suitable high yielding rice varieties. Throughout the growing season, aerobic rice field is kept under unsaturated condition and field is irrigated by surface or sprinkler system to keep soil wet. Therefore, water productivity is reported to be higher in aerobic rice by 64-88 per cent (calculated as grams of grain produced per kg of water input) and utilises 3,000 to 3,500 litres of water to produce 1 kg of rice compared to rice raised under transplanted flooded system.
Mechanised way of sowing
Further, aerobic rice cultivation system involves mechanised way of sowing with no puddling, transplanting and not need of frequent irrigation, which reduce labour usage more than 50 per cent, compared to irrigated rice. However, aerobic rice cultivation needs suitable rice varieties having the characteristics of both upland and high yielding lowland varieties to get good yield under the new unconventional system of cultivation.
Hence, these early-maturing varieties are with good seedling vigour, responsive to high input and tolerate flooding. International Rice Research Institute (IRRI) situated in Manila, Philippines identified several cultivars with high yield potential for this unconventional aerobic rice cultivation. A new improved upland rice variety, Apo developed by IRRI under aerobic rice cultivation system raised during dry season able to attain yield of 5.7 t/ha at IRRI farm.
In India, National Rice Research Institute (NRRI) (formerly Central Rice Research Institute (CRRI)), Cuttack, situated in Odisha, has developed rice varieties suitable for aerobic rice cultivation and so far six varieties were released suitable for this system, — CR Dhan 200 (Pyari) (4.0 t/ha), CR Dhan 201 (3.8 t/ha), CR Dhan 202 (3.7 t/ha), CR Dhan 203 (Sachala) (4.0 t/ha) CR Dhan 205 (4.2 t/ha) and CR Dhan 206 (4.2 t/ha) — which gives higher average yield compared to upland high yielding varieties. Two aerobic rice varieties MAS 26 and MAS 946-1 were also released from the University of Agricultural Sciences (UAS), GKVK, Bangalore, for the State of Karnataka, which is also said to be performing well under this system.
However, constrains in aerobic rice cultivation is increased weed growth, poor crop stand, crop lodging, high percentage of panicle sterility and root-knot nematode infestation. Importantly, high weed infestation is the major constraint for aerobic rice and cost involved in weed control is higher. Further, due to high infiltration rate of water and imbalanced availability of nitrogen makes the aerobic soil further ailing for micronutrients (iron and zinc) and rise in nematode population. Therefore, efficient nutrient management techniques along with integrated weed management are researchable areas for successful aerobic rice cultivation and research is in progress.
However, the yield of aerobic rice is comparable with transplanted rice and it has been reported from several countries. Thus, it is an alternative option to reduce labour drudgery and to increase water productivity. Further, in environmental point of view, emission of methane is lower substantially in aerobic rice.
Therefore, in recent days it is gaining momentum among rice researchers and farmers. However, extra care should be taken, since poorly managed field may cause partial to complete failure of crop, which might happen due to weeds and micronutrient non-availability.
A. Anandan, S.K. Pradhan and O.N. Singh
Crop Improvement Division,
National Rice Research Institute,