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Fertilizer use differs from country to country, and from too little to too much. Nitrogen and phosphorus can produce big crops. But they can also pollute water and air. A recent policy discussion in the journal Science compared the nutrient balances of different agriculture systems. Researchers compared the use of fertilizer in three areas that grow maize as a major grain: China, Kenya and the United States. By two thousand five, they say, farms in northern China produced about the same amount of corn per hectare as farms in the American Midwest. But the Chinese farmers used six times more nitrogen,... 

Companion planting is the idea that when some crops are planted together, they help each other grow. These compatible plants generally have similar needs for nutrients, soil and moisture. Advice for companion plantings is sometimes based more on tradition than proof. But Fabian Fernandez at the University of Illinois says there is evidence for some combinations. These can lead to better crops, reduce disease and help with pest control by attracting helpful insects. For example, some kinds of soil bacteria take nitrogen from the air and make a form that plants can use. The plants keep the nitrogen... 

Farmers in Afghanistan already struggle with the effects of drought and years of conflict. Now there is worry about a new threat headed in their direction in the wind — a fungus that destroys wheat crops. The disease is a form of stem rust named for its discovery in Uganda ten years ago. Ug99 is now in one of Afghanistan's neighbors, Iran. The disease kills wheat plants by robbing them of water and nutrients. Stem rust produces reddish-brown spots on the stems of infected plants. The weakened stems break easily. The world's last major outbreak of stem rust took place in the... 

Just because a plant looks nice does not mean you should eat it. Farmers learn this lesson tragically sometimes when their animals feed on wild plants. In fact, some of the nicest looking plants in the world are the most harmful. They are best enjoyed from a dstance. A good example is belladonna. A «bella donna» is a beautiful woman in Italian. The plant is also beautiful. It has flowers like stars. It also has shiny berries that start out green and turn purple to black. But every part of the belladonna plant is poisonous. Other names for belladonna include devil's herb and deadly... 

Three years ago, a study of overfishing led to sharp debate. It warned that the world's ocean fish could be almost gone by the middle of the century. Now, a new study offers more hope. It shows that the risk of fisheries collapse has recently decreased in some areas — some, but not all. Boris Worm at Dalhousie University in Canada and Ray Hilborn at the University of Washington in Seattle were lead authors of the new study. Professor Worm also led the earlier study published in two thousand six. Professor Hilborn publicly disagreed with those findings. The result: the two scientists... 

Farmers, especially in developing countries, are often criticized for cutting down forests. But a new study suggests that many farmers recognize the value in keeping trees. Researchers using satellite images found at least ten percent tree cover on more than one billion hectares of farmland. That is almost half the farmland in the world. The World Agroforestry Center in Kenya led the study. The findings were reported in August in Nairobi at the second World Congress of Agroforestry. Earlier estimates were much lower but incomplete. The authors of the new study say it may still underestimate... 

Planting trees around poultry farms can improve air and water quality — and relations with neighbors. Research has shown that just three rows of trees near poultry houses can reduce the release of dust and ammonia. They can also reduce the strong smell of ammonia gas. The trees capture dust, ammonia and odors in their leaves. They also provide shade from the sun, so they reduce cooling costs in summer. And they act as a windbreak, so they reduce heating costs in winter. Trees can also improve water quality around farms by removing pollutants from soil and groundwater. Several years... 

Colony collapse disorder first struck honey bees in the United States in late two thousand six. Over the next two years, beekeepers lost more than one-third of their honey bees. Scientists in the United States and other countries have been working to explain the mysterious disappearances of bees. Now, a new study suggests that several viruses may act together. Scientists from the University of Illinois and the United States Department of Agriculture did the study. Their report appeared in the Proceedings of the National Academy of Sciences. The team compared bees from affected colonies with... 

Norman Borlaug led what was known as the Green Revolution. As a plant scientist, he may have saved more lives than anyone else in history — as many as a billion, by some estimates. He traveled the world to help poor people develop better ways to produce food. He worked in the fields to show farmers new ways to grow wheat, rice and other crops. And he worked in the laboratory to breed new wheat varieties that could resist disease. Lately he worried about a new threat, a fungus called Ug99. It was discovered in Uganda ten years ago and has spread in Africa and now Asia. Mister Borlaug... 

From the beginning of human history, people have used oils from seeds and nuts. Most of the time these oils are used as food, especially in cooking. But sometimes they have other uses. For example, oils are used in paint and in cleaning products like soap. Oil is separated from seeds by using pressure. A machine called a press is often used. Sometimes it is surprising to learn how much oil the seeds contain. Sesame, cotton and sunflower seeds, for example, all contain at least fifty percent oil. Soybean is an important seed around the world, but it is only twenty percent oil. So chemicals are... 

Pruning makes no sense. You cut off parts of a plant. Yet the plant is supposed to grow back even better than before? This demands an answer. The explanation begins with the apical bud. This bud is at the end of the actively growing tip of the plant. Apical buds produce a growth hormone called auxin. The buds release this hormone down the plant stem. When the top of the main shoot is removed — by pruning or breakage — the auxin is no long produced. This causes buds to the side, called lateral buds, to wake up and start growing. The result: better plant development. Pruning... 

We talked last week about when and how to prune plants. Today we tell you about some new understanding of why cutting the main branch of a plant or tree can lead to better development. The findings are from researchers on two continents. Professor Prezemyslaw Prusinkiewicz of the University of Calgary in Canada led the research with scientists from Britain and Sweden. Their study appears in the Proceedings of the National Academy of Sciences. Researchers have known since the nineteen thirties that the actively growing tip of a plant releases a hormone called auxin. This hormone flows down the... 

Scientists now have a genetic map of the potato. The project is the work of a team from fourteen countries, the Potato Genome Sequencing Consortium. Potatoes are one of the world's leading food crops. But potato breeders currently spend ten to twelve years developing new kinds. Now they will be able to locate genes for any desired trait, improving quality, nutritional value and disease resistance. A genome contains information about every position along chromosomes, the structures that hold genes. Genes direct the making of proteins which do much of the work in building an organism, whether... 

Plant breeders and genetic engineers keep working to give crops the strength to resist threats like insects, diseases, droughts or floods. But before you can resist a threat, you need to understand it. We told you last week about a newly completed genetic map of the organism that causes late blight. That disease led to starvation in Ireland from potato shortages in the middle of the eighteen hundreds. The new genome could lead to better ways to protect potatoes, tomatoes and other crops. Science may supply a stronger crop. Yet that does not always guarantee demand. Nik Grunwald from the United...