The Green Revolution is one of the great scientific success stories of the 20th century. The development of high-yield, disease-resistant varieties of wheat and rice by agronomist Norman Borlaug and others beginning in the 1940s dramatically increased food production worldwide and saved hundreds of millions of lives.

But Borlaug's approach didn't work everywhere. Low crop yields in developing nations remain a primary cause of world hunger. And with a constantly rising global population, food security is now a 21st-century problem. It's time, plant nutritionist Jonathan Lynch argues, for a second Green Revolution.

If the first revolution was so successful, why do we need a different approach? Why not just more of the same?

The first Green Revolution was based on soil inputs -- fertilizers and irrigation. It comes out of the explosion of input use after the Second World War. By the 1960s, population experts were predicting a global food crisis, and the question was "How can we improve production?"

The answer was very straightforward. Put on fertilizer. Borlaug and others developed dwarf plants that don't fall over from the weight of higher yields. You put fertilizer on them and irrigate and yields go way up. This technology saved hundreds of millions of people from starvation -- it's been a huge, huge thing. But it really hasn't reached many of the poorest nations, like those in Africa. In these places, intensifying inputs is not a viable option.

Simply as a matter of cost?

The soil is very poor. And they can't afford fertilizers. It's not just Africa, either. If you look at a map of phosphorus in soils across the world, you'll see that most of the world is deficient. And the global supply is running out -- we can't make more. What we need, instead of plants that respond well to fertilizers, are plants that can do well in low-input, low-fertility environments.

Plants that don't need nutrients?

All plants need nutrients. What we're dealing with, really, is acquisition efficiency. Getting those nutrients out of the soil better.

This is not just an issue for the developing world, by the way. Sixty percent of the nitrogen fertilizer applied to corn in the U.S. is never taken up by the plant. It goes into the water, the air, causes pollution. If we could go from wasting 60 percent of that nitrogen fertilizer to wasting 50 percent -- just a 10 percent improvement -- that would save something like $250 million a year. Not to mention the environmental benefit.