Crop Cycles, Climate Hit Soil, Water In North India

Intensive cropping in Punjab and Haryana is causing perceptible hydrological and soil imbalances, which, compounded by climatic changes, could lower agricultural productivity in the region.

These are the findings of an Indian Council of Agricultural Research (ICAR) team that studied crop productivity trends in the two states. The three-member committee was headed by noted plant physiologist and ICAR's National Professor S K Sinha. The other members were ICAR's deputy directors-general, Mangala Rai and G B Singh.

The committee observed that total average yield of rice and wheat in the region, estimated at over eight tonnes a year, was among the best in the world. But intensive cropping had resulted in a shift to crops that require more water, fertilisers and other inputs, rendering the new agriculture unsustainable in the long run, it added.

Instead of the usual one crop each of paddy and wheat, most farmers in the region now take two crops of paddy and one of wheat. This is done by planting the first paddy crop in May, the second in July-August, and followed up by a late wheat crop in December-January.

The first rice crop, known popularly as summer rice, is sown when the temperature is usually above 40 degrees Celsius. Water demand for this crop is very high because of rapid evaporation. Studies estimate the water requirement for summer rice at around 310 cm against 238 cm for the normal June crop.

Besides, overall solar radiation in the region has declined by 10 per cent over the past two decades. While the minimum temperature has risen by about 1.5 degrees Celsius, the maximum has declined marginally over this period.

The soil composition too has been altered by the change in cropping pattern. The committee pointed out that the organic carbon content of the soil in intensive rice-wheat cultivation areas declined to 0.2 per cent from 0.5 per cent in the 1960s. The phosphorus content is also dwindling. The extent of soil low on phosphorus has risen from 3.5 per cent to nearly 73 per cent now.

The lowering of temperature and increase in humidity around summer paddy fields because of standing water creates conditions conducive for pests and disease-causing pathogens, threatening the health of crops and humans.

The committee warned that crop productivity may be difficult to sustain in the region under present circumstances. It noted that the decline in rice productivity in Punjab and Haryana may accentuate unless remedial measures are taken. Wheat productivity, more or less steady so far, may start declining in a decade if the cropping pattern continued, the committee warned.

It suggested inclusion of leguminous plants in the crop cycle to help improve soil health. Summer rice should be replaced with a pulse crop, it pointed out. Government policies too should be reoriented to bring about a desired change in the crop pattern, it suggested.