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Don't Apply Phosphorus Without First Testing Your Soil

Making It Grow Minute
SC Public Radio

In many parts of the country, gardeners can’t buy fertilizers that contain phosphorus unless they have soil test results that show the need for that middle number on the fertilizer bag. Nitrogen, phosphorus, and potassium are the three nutrients the percentage of each is listed in that order on every fertilizer package. Nitrogen and potassium are both relatively water soluble and seldom are found in soils in high levels.  But phosphorus doesn’t move easily downward through the soil profile with rainfall or irrigation and can reach extremely high levels when gardeners don’t follow soil test recommendations. Your local Extension office may not be open to the public, but you can call them or Clemson’s Home and Garden Information Center for directions on how to submit a soil sample directly. Don’t waste money and risk excess nutrients harming rather than helping your plants. 

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Amanda McNulty is a Clemson University Extension Horticulture agent and the host of South Carolina ETV’s Making It Grow! gardening program. She studied horticulture at Clemson University as a non-traditional student. “I’m so fortunate that my early attempts at getting a degree got side tracked as I’m a lot better at getting dirty in the garden than practicing diplomacy!” McNulty also studied at South Carolina State University and earned a graduate degree in teaching there.