A combination of buoyant demand and supply-side jitters is supporting prices of soybeans and corn after several years of glut-driven pessimism.

Soybean and corn prices have rallied by more than 20 percent since the first quarter of the year due to production declines in South America contributing to tightness in the U.S. market, agri-giant Bunge's Chief Executive Soren Schroder said on the sidelines of a JPMorgan conference in Beijing.