Dale Richardson, age 8 of Nashville, Terin., for his question:
What is in the soil which makes things grow?
A plant is rooted in the ground and, of course, it cannot go shopping for groceries. Nor earl it go off on a hunting trap. What's more, a plant cannot eat meat and vegetables the way we can. It takes in simple chemicals and turns them into the nourishment it needs. We call these simple chemicals the raw materials from which the plant makes what it needs to thrive and grow. Some of these chemicals are found in the soil and some in the air.
The most important thing the plant needs is sugar. It makes this from carbon dioxide in the air, sunlight and water. Carbon dioxide is the waste gas which we breathe out and the plant gets water by soaking it up through its roots. In making this special sugar, the plant returns oxygen to the air. The oxygen we breathe in comes from plants who have used our waste carbon dioxide to make sugar.
This sugar, however, is not enough to supply the plant with everything it needs. It must also have a number of chemicals from the soil. These chemicals are dissolved in water and the plant takes them in through its roots, A plant cannot use any solid groceries at all. It uses gases from the air and chemicals in liquid form from the soil.
The eight most important chemicals which a plant needs from the soil are oxygen, carbon, hydrogen, nitrogen, phosphorus, sulphur, calcium magnesium and iron. Most plants also need small traces of the chemicals boron, chlorine, copper, iodine, magnesium, silicon, sodium and zinc. As you see, these chemicals are very different from our groceries for w e could not possibly make a meal from zinc, iron, iodine or copper.
The plant, however, takes these raw materials and makes them into woody materials, tender leaves, sturdy seeds and fragrant blossoms.
The entire animal world would soon perish if plants could not make these fats, proteins and carbohydrates from simple chemicals in the soil and in the air. For many animals feed directly on plants. And animals that do not eat plants feed upon animals that do.
Every crop of plants takes tans of chemicals from the soil in order to grow. 1n order to make 3.5 bushels of wheat, the crop takes 60 pounds of nitrogen from the soil, 322 pounds of potassium and 112 pounds of phosphorus, If the wheat crop were not harvested, the plants would wither, fall to the ground and decay, The materials used to make the plants would be broken down again into simple chemicals. The rain would dissolve them and they could be used again t o build a nest generation of plants. This is what happens in the wilds and the wilderness.
When the farmer gathers the harvest, he removes the old plants and the chemicals they contain from the soil: If he wants the soil to grow a new crop, he must replace this loss. He does this by putting fertilizers into the soil. The fertilizers may be natural decaying materials, such as manure, or they may be the simple chemicals which the plants will use as raw materials.