Surveys show that over forty percent of cultivated land has been degraded, mainly via the overuse of chemical fertilizers, Guangming Daily reported.

Cultivated land in China is classified into three grades - high, medium and low yield croplands, at 498 million mu (33.2 million hectares), 818 million mu and 510 million mu respectively, according to the Ministry of Agriculture. Medium and low yield croplands account for over 70 percent of the total area.

The internationally recognized ceiling for safe chemical fertilizer use is 225kg per hectare, but in China the figure is over 400kg, nearly double the top-most limit, said Jiang Gaoming, chief researcher at the Botany Institute of the Chinese Academy of Sciences.

Overuse of chemical fertilizers and their low absorption rates are the two main problems, Jiang noted.

At present, the amount of chemical fertilizers and pesticides used in China are around one third of the global average, according to Zhang Xiaoshan of the Rural Development Institute. also at the Chinese Academy of Social Sciences.

Agricultural output will not improve through increasing the use of chemical fertilizer beyond prescribed standards and causing harm to the environment, Zhang added.

With insufficient cultivated land in China, improving arable land quality is essential to increasing agricultural production and guaranteeing national food security, said Zeng Yande, head of the Planting Industry Management Department at the Ministry of Agriculture.

In accordance, experts have called for nationwide laws and regulations on cultivated land quality protection to be formulated. (ecns)