Forecasts of heavy rains across key central and western growing regions of India have stoked fears of potential crop losses in the second half of September, farm experts and industry officials said.

Last week, the state-run weather office said the monsoon, which turned patchy in the first week of September, will pick up in most parts of India, with rains expected in some of the key farm belts.

Spurred by monsoon rains, which deliver about 70 percent of India's annual rainfall, farmers have planted a record acreage with summer crops such as rice, corn, cotton, soybeans and sugarcane.

Rains were 17 percent above average in June - the first month of the annual rainy season - but July rains were 10 percent below average. The monsoon picked up again in August and were 27 percent above average.

Heavy rains in August damaged some cotton, pulse and soybean crops in a few pockets. In the absence of any official estimate, trade, industry and government officials say the rains had localised impact and the damage was not widespread.

But heavy rains could cause extensive damage later this month when the crops ripen.

Torrential rains would damage soybean and peanut which now need a relatively dry spell, said B.V. Mehta, executive director, the Solvent Extractors' Association of India.

Still, soybean production could be higher than last year's 9.3 million tonnes, Mehta said.

Cotton plucking would pick up in the next two weeks. If farmers receive excessive rainfall, both yields and quality will suffer, said Pradeep Jain, chief of the Khandesh Ginning and Pressing Factory Owners and Traders Association.

"Some pulse crops suffered a bit of damage in August, and now there are concerns about heavy rains in the latter part of this month," said Vivek Agrawal, who owns JLV Agro, a trading firm.

"We are keeping our fingers crossed."