As is known to all, plants normally grow in soil. However, soil is not always 1 . To solve the problem, people grow plants using a liquid nutrient solution (营养液) instead of soil. This 2 is called hydroponics (水栽法).
Today, hydroponics is becoming more popular all over the world. But the idea is not 3 . People have been growing plants in water for thousands of years. 4 , the ancient Aztecs made floating islands to grow crops. Egyptians also have historical records of growing plants in 5 .
Modern hydroponics can be both simple and complex. There is a good chance you practice hydroponics without even 6 it. Have you ever taken a cutting of a plant and stuck it in a glass of water 7 roots grew? People in some countries often 8 hydroponic vegetables. Large hot house businesses use advanced hydroponic techniques (技术) to 9 vegetables for the market. The basic ideas are the same: growing plants without the use of 10 .
Hydroponics has several 11 . First, larger amounts of crops can be produced. Over the years, farmers have found that it can help12 the production of crops. Another 13 thing is that hydroponics uses much less water than traditional methods. Some people also say that hydroponic vegetables are of higher quality.
But the system's disadvantages do 14 . For a farm, hydroponic systems are generally 15 . Farmers will spend a lot of money setting up a new system. To keep the systems 16 , they have to spend more. 17 , plants are more likely to get sick. 18 move quickly since the plants share nutrient solutions. Another 19 of hydroponics is that the energy costs are high. 20 growing systems use the sun's energy, but hydroponic plants use oil-based energy.
