New Delhi, Aug. 19: India’s July rainfall, crucial for agriculture, is decreasing over more than 85 per cent of the land area, according to a study that has also revealed other slumps and spurts in rainfall patterns across the country.

The study by researchers at the Indian Institute of Tropical Meteorology, Pune, has indicated that annual rainfall is decreasing across 68 per cent of the area and increasing over 22 per cent of the area.

“The increasing and decreasing trends are not uniform. They show up at different times in different regions,” said Nityanand Singh, head of a team at the meteorology institute that has used extrapolations to analyse rainfall over India from 1813 to 2006.

The trends captured by the institute, though based on a controversial technique, appear to corroborate previous studies that have indicated reductions in rainfall during July, scientists not associated with the study said.

“A drier July would mean we may need to tailor farming practices to specific crops and specific regions,” said Laxman Singh Rathore, the head of agricultural meteorology services at the India Meteorological Department, New Delhi.

“Paddy is among the most important monsoon crops,” Rathore said. A new technique of transplanting paddy, practised in Andhra Pradesh and Tamil Nadu, might need to be expanded to other parts of the country that receive low rainfall in July, he said.

The new technique involves transplanting rice into shallow water fields after 10-15 days instead of the traditional 21 days. It is specially designed to help cultivation in relatively low-water conditions, he said.

Rainfall has been increasing steadily over the Bengal basin (south Bengal) since 1963, according to the findings, published by the institute as a scientific report but not yet published in a peer-reviewed journal.

The analysis has also indicated that rainfall has been decreasing over Kerala and Karnataka since the 1920s and increasing in northern Assam.

The study has shown that July rainfall is decreasing across the Himalayan region, north Bihar plains, Punjab plains, Gangetic plains, parts of central India, Karnataka and Kerala, among several other regions. The July rainfall is increasing in the Bengal basin, south Bihar plains, Narmada valley, Kutch peninsula and Gujarat plains.

But some scientists said the institute had attempted to extrapolate rainfall in different regions during periods when rainfall was not even being monitored in those areas. Less than five weather stations were tracking rainfall between 1813 and 1820.

“Not everyone is comfortable with this technique and the results,” said a senior meteorological department scientist. “But some results, particularly the decreasing trends in July, are consistent with previous observations based on actual weather data.”

Apart from paddy, crops that depend heavily on July rainfall include groundnut, cotton, bajra, jowar and several pulses, said Vyas Pandey, the head of agricultural meteorology at the Anand Agricultural University in Gujarat.

One option for farmers in areas where July rainfall is decreasing would be to shift to jowar, bajra and pulses such as green gram and pigeon pea that require lower amount of water, Pandey said. But scientists concede that changing farming practices isn’t going to be easy.