With these discoveries⑮， some farmers and many customers are beginning to turn to organic farming. Organic farming is simply farming without using any chemicals. They focus on⑯ keeping their soil⑰ rich and free of disease. A healthy soil reduces⑱ disease and helps crops grow strong and healthy. Organic farmers, therefore, often prefer using natural waste from animals as fertilizer. They feel that this makes the soil in their fields richer in⑲ minerals and so more fertile⑳. This also keeps the air, soil, water and crops free from\s\up1(21(21) chemicals.

　　Organic farmers also use many other methods to keep the soil fertile\s\up1(22(22). They often change the kind of crop in each field every few years, for example, growing corn or wheat and then the next year peas or soybeans\s\up1(23(23). Crops such as peas of soybeans\s\up1(24(24) put important minerals back into the soil, making it ready for crops\s\up1(25(25) such as wheat or corn that need rich and fertile soil. Organic farmers also plant crops to use different levels of soil, for example, \s\up1(26(26)planting peanuts that use the ground's surface followed by vegetables that put down deep roots\s\up1(27(27). Some organic farmers prefer planting grass between crops to prevent wind or water from carrying away the soil, and then leaving it in the ground to become a natural fertilizer for the next year's crop. These many different organic farming methods have the same goal: \s\up1(28(28)to grow good food and avoid damaging\s\up1(29(29) the environment or people's health.

　　⑮discovery/dI'skʌvərI/n.发现；发觉

　　⑯focus on(＝concentrate on)集中(注意力、精力等)于

　　⑰soil/sɔIl/n.土壤

　　⑱reduce/rI'djuːs/vt.减少；减缩

　　⑲be rich in富含......；......的含量高

　　(反)be poor/low in ......的含量低；缺乏......

　　⑳fertile/'fɜːtaIl/adj.肥沃的；富饶的

　　\s\up1(21(21)keep ...free from/of使......免受(影响、伤害等)；使......不含(有害物)

　　\s\up1(22(22)动词不定式短语to keep the soil fertile作目的状语；keep是使役动词，这是"keep＋宾语＋宾补"结构。

　　\s\up1(23(23)现在分词短语growing corn or wheat and then the next year peas or soybeans作状语。

\s\up1(24(24)soybean/'sɔIbiːn/n.(＝soyabean)大豆