In the last 30 years, the United States has grown more food using less land and with less environmental strain than ever believed possible. Fertilizers are better, pesticides are better and genetic modification has led to less need for both.

But some scientifically developing nations, including much of Europe, are still using more antiquated approaches, and then means a lot of nitrogen. Nitrogen boosts plant growth and yield even on poor soils, which helps plants avoid the typical characteristics of nitrogen deficiency - stunted growth and pale or yellow leaves - but in environmentally intensive approaches like organic farming, the left over nitrogen can be substantial. 

New insights into how plants regulate their absorption of an essential nutrient could help avoid pollution caused by excess use of fertilizers. It could even show farmers how to optimize their nitrogen. Like carbon dioxide, nitrogen is good for plants but too much is bad. This would allow optimum plant growth without producing excess nitrogen in run-off from fields, which is a source of water pollution. 

The new study by researchers at the University of Edinburgh and the University of Campinas in Brazil examined how nitrogen is absorbed and converted into cellular building blocks in plants. They found that when nitrogen is absorbed, plant cells produce nitric oxide, which acts as a signaling molecule. This nitric oxide fine-tunes how much nitrogen is used for growth, by signaling to the plant's cells when to limit its uptake. 

The scientists say that because nitric oxide plays important roles in shaping the development of plants, and how plants respond to environmental stress, these insights highlight key considerations of how nitrogen-based fertilizers should be used in agriculture.

Dr Steven Spoel of the University of Edinburgh's School of Biological Sciences, who led the study, said, "Understanding nitrogen absorption better will ultimately allow us to breed crop varieties that need less fertilizer, and therefore are better for the environment."