Most people assume that plants need soil to grow strong and healthy. But hydroponic growing systems have proven that plants will grow without soil, if given all of the nutrients needed from the water they grow in.
Mineral nutrients are the nutrients provided by fertilizers. These are the nutrients typically found in soil. These nutrients may also be found in rainwater and other forms of runoff. Water dissolves these nutrients and carries them as it filters through soil. The major mineral nutrients are nitrogen, phosphorous and potassium. There are also nutrients that plants need in smaller amounts called micronutrients. These micronutrients include copper, boron, iron, chloride, molybdenum, manganese and zinc.
Carbon dioxide is made of carbon and oxygen molecules. Plants use carbon dioxide they collect from water and the air in the process of photosynthesis. Once a plant absorbs carbon dioxide, it transports the molecules to its cells. There, chemical reactions that involve chlorophyll convert the carbon dioxide into sugar and oxygen. The plants use the sugar and release the oxygen into the atmosphere. Plants use this sugar to build tissue and run their metabolisms.
Plants create hydrogen as a byproduct of photosynthesis and absorb it from water. But these forms of hydrogen are used in different ways. During photosynthesis, plants add hydrogen from water to the carbon and oxygen molecules to create starches as part of the process of creating sugar. The presence or absence of hydrogen ions in soil can cause the pH of soil to raise or lower, which has a direct effect on the way plants absorb the mineral nutrients of soil. Plants placed in soil that's either too acidic or alkaline will not absorb minerals effectively and will decline in health.