As part of our volunteer work, Jefferson County Master Gardeners record brief radio spots on gardening. Here's one we did on Fertilizer 101 - a basic tutorial for those new to gardening:
Every plant requires nutrients to grow and thrive. Three of the primary nutrients – carbon, hydrogen and oxygen – come from air and water. Gardeners will need to provide the other three – nitrogen, phosphorus and potassium .
The three numbers on a bottle or bag of fertilizer stand for nitrogen, phosphorus and potassium. in that order. The numbers also indicate how much of each is provided by weight.
Nitrogen helps plants produce protein needed for new tissue. Give a plant too much nitrogen and it will produce great foliage but no fruit or flowers. Plants can take up only so much nitrogen, and the rest leaches into the soil and can reach ground water. Give a plant only as much nitrogen as it needs.
Phosphorus stimulates root growth, aids in setting buds and flowers and increases the overall vitality and seed size.
Potassium helps make plants strong and vigorous and more disease resistant.
The best way to choose a fertilizer is to do a soil test to see what nutrients are lacking in your yard or garden. Many gardeners use far more fertilizer than plants need, which creates a serious problem for the environment through runoff.
An all-purpose, balanced fertilizer such as 10-10-10 will provide the needed nutrients. If you need more of one nutrient and less of the other, you can choose a mix that fits your needs.
When you apply fertilizer, consider foliar feeding. Plants can absorb nutrients up to 20 times more efficiently through leaf surfaces than through their roots. You’ll get the best results applying the spray during critical growth stages such as immediately after transplanting, during bloom time and the period right after a plant sets fruit.