Why Are Phosphorus & Nitrogen So Important to Plants?

Nitrogen

• Nitrogen is part of both the plant's structure and its life processes. Nitrogen is found in the leaves, seeds, stems, flowers, roots, and tissues of plants. It is needed for growth and for seed and fruit production. Nitrogen is an essential part of the molecular structure of chlorophyll, which is vital to photosynthesis, the process by which a plant makes its own food. Nitrogen in the roots of a plant helps the plant take up water and other nutrients from the soil. Although about three quarters of the air we breathe is nitrogen, most plants cannot absorb the nitrogen from the air and must take it from the soil. Legumes such as beans and certain grasses are among a few plants that can take nitrogen from the atmosphere and fix it into the soil for later use.

Phosphorus

• Phosphorus also is important to photosynthesis and plant growth. It promotes the growth of healthy roots and encourages flowering plants to blossom. A phosphorus deficiency leads to stunted growth, dull or dying leaves, and the formation of a red pigment at the leaf base. By the time symptoms of a phosphorus deficiency are discovered, it is usually too late to save the plant. Young plants deprived of phosphorus during development may never recover.

Potassium

• The final primary plant nutrient is potassium. Potassium is important for photosynthesis, building protein, producing fruit and fighting diseases. Additionally, potassium, also known as potash in fertilizers, is used by plants to build stronger stalks and stems, to move food through the plant, and to help increase drought resistance. Although potassium is used for many life processes within the plant, it is not part of the plant structure.

Application

• Gardening and growing various crops will deplete the soil of the vital nutrients. Most plants are unable to absorb these nutrients from the air and rain water. Leaving grass clippings to compost on the lawn and allowing leaves to accumulate and decompose in the landscaping are natural ways to replenish these nutrients, but many homeowners find them to be unsightly solutions. Commercial fertilizers usually have three numbers on their labels, called the fertilizer grade, indicating the amount of each nutrient present in the mixture. The first number is nitrogen, the second is phosphorus, and the third is potassium. For example, a fertilizer that has a fertilizer grade of 10-5-5 is 10 percent nitrogen, 5 percent phosphorus, and 5 percent potassium.