During the Warring States, Qin and Han Dynasties from 475 BC to 220 AD, organic fertilizer was widely used in agriculture, and fertilization technology was highly valued. During more than 2,000 years of application of organic fertilizer, the yield of wheat was less than 1 times, and that of rice was nearly 4 times, but it only increased 1 kg in about 12 years (Table 7-2 Chemical fertilizer has been widely used in China for only a few decades. At the beginning of the founding of New China, little or no chemical fertilizer was used, and the total grain output was only about1.500 million tons. 1978 mainly applied organic fertilizer, with only 8.84 million tons of chemical fertilizer, and the total grain output reached 300 million tons; During the period of 1998, chemical fertilizers were mainly applied, with the application amount reaching 40.85 million t and the total grain output reaching 500 million t[6], which ensured China's "food security".

Table 7- 10 Changes of Rice and Wheat Yield in Ancient Organic Agriculture in China

2. In the past 50 years since Hunan Province 1949, chemical fertilizers have played an important role in promoting the sustained growth of grain and agricultural products.

According to a document of Hunan Provincial Department of Agriculture (200 1), when nitrogen fertilizer was popularized in 1950s, the total grain output reached 1000 billion kg. When phosphate fertilizer was popularized in the 1960s, the total grain output jumped to 654.38+0.5 billion kg. In the 1970s, potash fertilizer was vigorously promoted, and the total grain output exceeded 20 billion Jin. Since 1980s, with the balanced fertilization of nitrogen, phosphorus, potassium, medium and trace elements, the total grain output has reached a record high of 25 billion kilograms.

3. The worldwide experience proves that the application of chemical fertilizer is the fastest, most effective and most important measure to increase production in both developed and developing countries.

Norman. In 1994, Borlauq, a world-famous scientist of fine species and Nobel Prize winner, concluded that "50% of the increase in global crop yield in this century (20th century) comes from the application of chemical fertilizers". American scientist R.G.Hoeft thinks that if the application of nitrogen fertilizer is stopped immediately, the global crop yield will be reduced by 40% ~ 50%; American economists estimate that 50% ~ 60% of the increase in crop yield in the United States is the result of chemical fertilizer application; According to FAO data, the application of chemical fertilizers in developing countries can increase the yield of food crops by 55% ~ 57%.