The best crops are grown in rich, well-watered soil. Just as people and animals need food to grew strong and healthy, plants, too, need their own kind of food to grow and ripen.
Air contains a gas called carbon dioxide. Plants breathe in this gas through their leaves. They suck in the water from the soil through their roots. Sunlight helps the plant use the water and the carbon dioxide to grow.
A plant that stands in the sunlight is healthy. But a plant that is in the dark soon droops. Its leaves grow pale and withered.
People and animals rely on healthy crops to provide their food supply. Cattle and sheep eat rich grass. They produce good milk and meat. People eat the meat and fruit and vegetables ripened by the sun. They drink milk and enjoy dairy foods such as cream, butter and cheese.