All living things need proper nutrition. We “feed” our plants because our garden soils may not be fertile enough to supply all our plants’ nutritional needs.
Nitrogen, Phosphorus and Potassium (N-P-K) are the Primary Nutrients plants use in the largest quantity (sort of how we use proteins, carbohydrates, and fats.) They are part of the plants balanced diet.
N-P-K are the three numbers on your box or bag of fertilizer.
Nitrogen (N) is always the first number. Nitrogen promotes new growth and green leaves. Nitrogen is water soluble, washing down below the root zone of the plants with rain and irrigation so it must be replenished regularly. Nitrogen is the element most likely to be lacking in our soil. A common sign of nitrogen shortage is light green or yellow leaves.
Phosphorous (P) is the second number. Phosphorous helps build flowers, fruit and strong roots. Phosphorous is not mobile in the soil so it is important to get it to the root level when possible. It is available to surface feeder and shallow bedding roots.
Most Santa Barbara soils have naturally occurring phosphorous.
Potassium (K) is the third number. Potassium promotes overall plant health, strong roots and resistance to disease. Proper use of fertilizer results in healthier, happier plants.