About 3.33 million hectares of China’s farmland is too polluted to grow crops, a government official said on Monday, highlighting the risk facing agriculture after three decades of rapid industrial growth. China has been under pressure to improve its urban environment following a spate of pollution scares. But cleaning up rural regions could be an even bigger challenge as the government tries to reverse damage done by years of urban and industrial encroachment and ensure food supplies for a growing population. Wang Shiyuan, the vice-minister of land and resources, told a news briefing that China was determined to rectify the problem and had committed “tens of billions of yuan” a year to pilot projects aimed at rehabilitating contaminated land and underground water supplies.