Should cattle be moved off a field while fertilizer is applied via a pivot watering system?

The world cattle population is estimated to be about 1.3 billion head. India is the nation with the largest number of cattle, about 400 million, followed by Brazil and China, with about 150 million each, and the United States, with about 100 million. Africa has about 200 million head of cattle, many of which are herded in traditional ways and serve largely as tokens of their owners' wealth.

Europe has about 130 million head of cattle (CT 2006, SC 2006). Cattle today are the basis of a many billion dollar industry worldwide. The international trade in beef for 2000 was over $30 billion and represented only 23 percent of world beef production.

The production of milk, which is also made into cheese, butter, yogurt, and other dairy products, is comparable in size to beef production and provides an important part of the food supply for much of the world's people. Cattle hides, used for leather to make shoes and clothing, are another important product. In India and other poorer nations, cattle are also important as draft animals as they have been for thousands of years.

Cattle are "responsible for 18% of greenhouse gases, more than cars, planes and all other forms of transport put together," states a 400-page United Nations report from the Food and Agriculture Organization (FAO). 1 Cattle are blamed for a host of other environmental crimes, from acid rain to the introduction of alien species, from producing deserts to creating dead zones in the oceans, from poisoning rivers and drinking water to destroying coral reefs. A related study at the University of Chicago 2 suggests that eliminating meat and dairy from your diet saves 1.5 tons of greenhouse gases from being emitted each year - contrast that with the meager 1 ton of greenhouse gases saved annually by driving a hybrid car.

The University of Chicago study suggests that reducing meat consumption - even going from 2 burgers a week to 1 - is the best way consumers can act to slow down climate change. The UN report calls cattle the greatest threat to the climate, forests and wildlife. Climate Change: Burning fuel to produce fertilizer to grow feed, to produce meat and to transport it - and clearing vegetation for grazing - produces 9 per cent of all emissions of carbon dioxide, the most common greenhouse gas.

And their wind and manure emit more than one third of emissions of another, methane, which warms the world 20 times faster than carbon dioxide. Acid Rain: Livestock also produces more than 100 other polluting gases, including more than two-thirds of the world's emissions of ammonia, one of the main causes of acid rain.