Reuters: For the last decade and a half, a mysterious and worrisome trend has emerged in the farming world that has sent farmers, scientists and policy makers looking for answers.
Crop yields -- how much of a crop is harvested per hectare -- for some of the world's major grains like rice, wheat and corn have gone from increasing year after year to plateauing in many of the world's biggest grain producers.
Until about the middle of the 20th century, the only way farmers knew to increase production...