An essential nutrient an organism needs for life that is in the shortest supply in their environment. For example, a tomato plant requires specific amounts of nitrogen, phosphorus, and potassium to grow and produce fruit. A soil sample from a garden shows adequate amounts of nitrogen and phosphorus, but a very low amount of potassium. Potassium is the limiting nutrient in this instance because the tomato plants do not have enough potassium to perform the cellular processes needed for growth and reproduction. Growth will continue if more potassium is added to the soil. The nutrient in least supply is limiting the organism’s ability to grow and reproduce.