Beginning of Essay
Over the 10,000 years since agriculture began to be developed, peoples everywhere have discovered the food value of wild plants and animals, and domesticated and bred them. The most important crops are cereals such as wheat, rice, barley, corn, and rye; sugarcane ....

Middle of Essay
.... cover of residues to shield their soil from wind and water erosion. Crop rotation and cover crops are also being increasingly used to hold soil in place between plantings. Still, many small-seeded crops require a finely worked, pulverized seedbed, and soil erosion cannot be completely eliminated. Fertilizers from both natural and manufactured sources can also contribute to water pollution. Soluble-nitrogen forms can leach into groundwater, and all fertilizers, including animal manures, can be carried along in surface runoff. Crop farmers are paying more attention to reducing fertilizer loss, partly for environmental reasons but also because of ferti ....