AGRICULTURE Session 04: Soil Chemistry
Learning Objectives
- Students will investigate soil nutrients and the chemical compounds that comprise plant nutrient requirements.
Background:
- Utilize the knowledge gained from the previous lesson (Session 03) regarding soil composition, texture, and particle size. The correct amount of plant nutrients is essential for growing healthy crops. It is important to know if a crop should be fertilized and what type of fertilizer to use by conducting a soil test. Review the procedure for taking a soil sample and Background Information from Extension Agent, Cory Tanner.
- Review procedure
- Background Information for Soils Lesson
- The continued development of farming technology and precise management of fertilizer inputs is necessary for farmers to grow more food on less land to feed our growing population. In 1910, the discovery of the Haber-Bosch process for fixing atmospheric nitrogen gas into commercial fertilizer dramatically increased the amount of food that farmers could grow. It is estimated that nearly half the world’s population is dependent upon commercially produced fertilizers. Not all fertilizers contain the same amounts of primary nutrients (NPK). Fertilizers are prepared in different compositions so the consumer, farmer, or home gardener can apply precisely what is needed.
- Primary Nutrients: Nitrogen (N), Potassium (P), and Phosphorus(K)
These are the three most commonly deficient nutrients in the soil. After carbon, hydrogen, and oxygen, plants take up more potassium and nitrogen through their roots than any other nutrient. - NITROGEN ’N’ – Nitrogen forms new cells and is essential to total plant development. A shortage of nitrogen halts plant growth and cell production. Symptoms of nitrogen deficiency are a yellowish brown color along the veins and tips of leaves, stunted growth of the plant or paleness in color on older leaves. Too much nitrogen can cause tall, spindly plants that easily topple over and nitrate poisoning (look for a strong red tint to the leaves). Nitrogen is also essential to the compost pile, as it aids in the breaking down of old plant residues. Good sources of nitrogen include: blood meal, cottonseed meal, fish meal, soybean meal, rabbit manure and tea grinds. You can also grow a cover crop of legumes in the fall to raise the nitrogen level for the next spring’s crop.
- PHOSPHORUS ‘P’ – Phosphorus produces vigorous seed and root development. A shortage of phosphorus slows cell division and results in stunting of growth and late maturity of the plant. A symptom of phosphorus deficiency is spindly plants with purple streaks in the stems. Since phosphorus moves very slowly in the soil, it is essential to have it available during early plant development. Good sources for phosphorus include: bone meal, rock phosphate and colloidal phosphate. Incorporating organic matter (compost) into the soil makes the phosphorus present more readily available to the plants.
- POTASSIUM ‘K’