In a Fix: Agricultural chemicals disturb a natural relationship

Several pesticides can disrupt a partnership that enables certain plants to take up nitrogen by enlisting the help of bacteria. As well as stunting the growth of those plants, the newfound effect may be decreasing soil fertility, the researchers suggest.

Organisms require nitrogen to make proteins, but most living things can't use the abundant gas in the atmosphere. A natural process called biological nitrogen fixation converts the gas to ammonia, the form that plants need.

An industrial reaction can do the same trick for crops. Today, farmers apply seven times as much synthetic nitrogen fertilizer as they did 40 years ago. But the higher crop yields that once resulted from fertilizer use have stagnated in recent years, say