The element with the symbol "K" is potassium. Potassium is a chemical element with the atomic number 19 and falls under the alkali metals group in the periodic table. It is a soft, silvery-white metal that is highly reactive, especially with water. Potassium plays vital roles in biological systems, particularly in cellular function, as it helps regulate fluid balance, muscle contractions, and nerve signals. In agriculture, potassium is an essential nutrient for plant growth, often found in fertilizers to enhance crop yields and improve overall plant health.