Over long time, human food and clothing depended mainly on agriculture. While ever since the ancient time, agriculture had always relied on a lot of human labor, which was subject to various kinds of natural conditions. So the development of agriculture was very slow. During the 19th century, the use of agricultural machinery gradually improved the working conditions. However, in agricultural production, it was the application of chemical fertilizers and pesticides that really increased the agricultural output in per unit area.
Practice shows that, among all the measures to increase the agricultural production, the role played by chemical fertilizers is 40% to 65%. On the basis of the booming in the petrochemical industry, synthetic ammonia and urea have realized large-scale production, which makes the output of chemical fertilizer occupy a large proportion in the chemical products. In 1985, the total output of chemical fertilizer in the world amounted to approximately 140 million ton, which made it become one of the bulk chemical products. In recent years, the development of nitrogen, phosphorus and potassium compound fertilizer and trace elements fertilizer has further meet the demands of different soil structures and different crops.
In the early period, people used natural animals, plants and minerals to prevent and treat crop pests and diseases. Until the late 19th century, after the formation of modern chemical industry, people began to use arsenic preparation to kill beetles on potato, and use Bordeaux mixture to prevent and treat downy mildew on grapes, so that agriculture began a new era of chemical prevention and treatment. During the 1940s, a lot of pesticides and herbicides, such as organic chlorine, organic phosphorus, were produced and widely used in agriculture, forestry, animal husbandry and public health. However, some of the pesticides during this period were rich in residues or poison, which caused ecological pollution, so they had been banned by many countries.
In recent years, a number of efficient, low-residue, low-toxicity pesticides have been developed, including pyrethroid, which is a bionic pesticide and will not pollute the environment. It has been put into industrial production. As a result, bio-pesticides have become the most active areas in pesticide research currently.
What’s more, plastic film (such as high pressure polyethylene, linear low density polyethylene, etc.) has been applied in modern agriculture, which is used for mulching film or greenhouse seedlings. It can significantly increase the output of the crops, so it is now being popularized on a large area.