중학교 영어 3 (동아출판 윤정미) 연계 글

Picture a farm with no fields, no rain, and no sunshine. In an old city warehouse, rows of lettuce grow on shelves stacked almost to the ceiling. This is a vertical farm, a kind of smart farm that grows vegetables indoors. Here, machines do the jobs that the sun, the soil, and the weather do on an ordinary farm.

Plants need light to make their food, but they do not use every color of sunlight equally. They reflect much of the green light and use more of the red and blue light. Shining just above each shelf, LED lamps can give off mostly these two colors. Unlike the sun, the lamps can stay on for as many hours as the farmer chooses.

Measuring the air's temperature and moisture day and night, small sensors send their readings to a computer. The computer then adjusts the lamps, the air, and the water on its own. As the plants grow larger, the computer changes their light and nutrients to suit each stage of growth.

These plants do not grow in soil. Hanging in water rich in nutrients, their roots take up water and nutrients together. The water that the roots do not use is cleaned and sent back to the shelves.

Kept in closed, clean rooms, the crops can often be grown without pesticides. Since no storm or cold season can reach these rooms, the farm can grow crops all year round. Korea's Rural Development Administration has reported on lettuce grown on five shelves stacked one above another. Each shelf held about as much lettuce as the same area of an open field. The shelves, however, could be harvested six times as often in a year as the field. As more shelves are stacked on the same floor, the harvest from that floor grows larger.

This kind of farming has a price, though. Giving up free sunlight, an indoor farm must pay for every hour of light it uses. As the lamps stay on for more hours, the electric bill climbs higher. The machines that heat and cool the rooms add even more to the cost. Even so, a farm in an empty city building can grow fresh food near the people who eat it.