Water use is excessive in rice cultivation

RICE AS grown in India is a water-guzzler, because farmers use on an average 15,000 litres to produce one kg of paddy, though water technologists at the Indian Agricultural Research Institute in New Delhi say no more than 600 litres is needed if proper water management techniques are followed. Given that 45 per cent of the country's total irrigation water is used solely for rice cultivation, the need to improve farming methods is imperative.

Besides being wasteful, excessive use of water results in lower yields and adverse environmental effects such as soil salinity and waterlogging. Paddy yields in irrigated regions of Tamil Nadu, Punjab and Haryana range from five to six tonnes/ha, whereas in the high-rainfall areas of eastern UP, Bihar, West Bengal and Orissa, the yields are about 1.8 tonnes/ha. The main reasons for the poor yields are improper irrigation management and waterlogging.

"Optimising irrigation water use should be our aim," says B R Sharma, who co-ordinates an all-India research project on water management. Sharma feels farmers in India invariably tend to use more water, notably in canal-irrigated systems. Get water and overuse it seems to be the rule.

A large amount of water is lost in seepage and deep percolation. Loss from deep percolation is estimated at 50 per cent in heavy textured clay soils and about 85 per cent in light textured loamy sands and laterite soils. Sharma's project reports show upto 40 per cent of the water can be saved if farmers adopt proper techniques. Studies in eastern India show effective soil compaction and puddling can reduce percolation losses by 20 per cent and also reduce the risk of crop failure during droughts.

Farmers widely believe that water should be stored on paddy fields to prevent weed growth. But studies in West Bengal and Orissa show that standing water of more than 10 cm height leads to heavy leaching of soil nutrients and percolation losses. In all seasons, a two to five cm water depth and intermittent irrigation saves 10 to 50 per cent of water without adversely affecting yields.

Additionally, Sharma says, if irrigation is terminated 14-17 days before harvest, the grain would ripen uniformly and a considerable amount of water would be saved without lowering yield levels.

Proper crop-rotation can also reduce water consumption and result in higher yields. In Orissa, the net returns per unit of irrigation water (Rs/cm of water) were estimated at Rs 28.05/cm of water for rice-mustard-rice rotation, whereas for rice-potato-gingili rotation, it was Rs 52.81/cm. Better coordination between farmers, scientists and extension officials is needed to popularise water-saving techniques.