BEIJING - China will reap a bumper grain harvest for a 12th consecutive year in 2015, boosted by government policies encouraging production to feed the world's largest population, a think tank has forecast.

Total grain production is expected to rise 0.5 percent on an annual basis to 610 million tonnes this year, the Chinese Academy of Social Sciences (CASS) forecast in an annual report released on Wednesday.

The projected growth was down from last year's 0.9 percent rise, indicating an increasing challenge for the country to maintain sustained development in agriculture.

Li Peilin, deputy head of the CASS, said rising production costs, worsening pollution and shrinking farmland amid accelerating urbanization have all weighed on agricultural production.

To ensure food security, the Chinese government has been striving to guarantee the area of farmland, build high-grade farmland and increase the country's grain production capacity. It also raised state purchasing prices for grain to encourage planting.

According to the CASS report, China has maintained a high self sufficiency rate of over 97 percent for rice, wheat and corn, but that of soybean dropped to 14.1 percent last year from 16.2 percent in 2013.

The report also forecast output of China's oil seed crops, such as soybean and rapeseed, will grow by 1 percent year on year to 35.6 million tonnes in 2015.