How to Increase Phosphorus & Potassium in the Soil

Fertilizers typically list three numbers, such as 5-10-10. These numbers represent the percentage of nitrogen (N), phosphorus (P) and potassium (K) in the fertilizer. Most gardeners are aware that nitrogen promotes rich green foliage, but that too much nitrogen may inhibit blooming and fruiting -- but overlook the importance of phosphorus and potassium to plant growth. Without adequate phosphorus, plants may develop weak root systems, mature slowly and lose their ability to withstand the stress of winter. A potassium deficiency inhibits the plant's ability to withstand stress of hot and cold temperatures and compromises the plant's ability to regulate water and photosynthesis. Healthy growth requires balanced nutrients.

Soil test
Fertilizer
Garden tiller

Instructions

- 1
  Perform a soil test to determine the balance of nutrients in your soil. An inexpensive test from the hardware store provides the level of both phosphorous and potassium, but one completed by your county extension office provides a more thorough evaluation of your soil.
- 2
  Read the soil analysis report from the soil testing service or read the accompanying material with your soil test kit to determine your soil needs.
- 3
  Purchase fertilizer with a formula that is high in phosphorus and potassium, but low in nitrogen, if your soil test indicates that the soil lacks both phosphorous and potassium. Otherwise, purchase a formula that matches your soil's needs.
- 4
  Spread the fertilizer over the top of the gardening area. Follow the recommended application rate when applying fertilizer, as too much fertilizer can damage plants.
- 5
  Work the fertilizer into the top 6 inches of the soil with a garden tiller.

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