Overuse of fertilisers is robbing northeast grain heartland of its valuable topsoil

Overuse of fertilisers in northeast China - the country's most important grain-growing region - poses a serious threat to farming in the area, experts say.

Nutrients in the region's fertile layer of black topsoil were breaking down and becoming thinner at a rate of 1cm per year, the reported.

"It took 300 million years for the black soil to form to a depth of one metre, but now it's degrading by one centimetre each year," Chen Wenfu, an academic at the Chinese Academy of Engineering, told the newspaper.

"If this continues, sustainable agricultural development will be seriously threatened," said Chen, who is also a professor at Shenyang Agricultural University.

Land degradation and poor infrastructure were both hindering expansion of food production in the area.

The provinces of Heilongjiang , Jilin and Liaoning make up of what is commonly called northeast China, an area that accounts for 16 per cent of the mainland's arable land and 20 per cent of total grain output.

The region's rich, black soil contains between 3 per cent and 10 per cent organic matter, ideal for crops including rice, soya beans and corn.