What Causes a Phosphorus Problem on Plants?

Phosphorus is a naturally occurring nutrient in soil that plants need for a variety of processes. A key component of most commercial fertilizers -- along with nitrogen and potassium -- phosphorus can also be added to soil by incorporating certain organic materials. Phosphorus problems in plants usually stem from a deficiency in this nutrient, but excessive phosphorus can also cause issues.

Importance of Phosphorus

Phosphorus is essential to plants for cell division and the development of new tissue. In soils deficient in this nutrient, adding phosphorus can speed plant development, boost root growth and aid in overwintering. Phosphorus also speeds up blooming in flowering plants, and can boost the productivity of fruits and vegetables.

Phosphorus Deficiency

Phosphorus deficiency can cause a variety of symptoms, depending on the plant species. Common symptoms include stunted growth and a reddish or dark-green coloration in the leaves. Deficiencies in phosphorus can be temporarily caused by cold weather, and excessive rainfall can cause phosphorus to leach out of soils. Additionally, conditions such as acidic soil can make it difficult for plants to take up phosphorus even if the nutrient is present.

Testing and Correcting

Deficiency symptoms are difficult to diagnose because the lack of various nutrients can cause similar symptoms, as can a variety of pests and diseases. The best way to determine the nutrient content of soil is through soil testing. Soil test kits are available at most garden stores, and the results will reveal the amount of phosphorus available to plants as well as other nutrient levels and pH. The results should also include recommendations for soil amendments and quantities. Incorporating manure into soil is one way to replenish phosphorus, and crushed phosphate rock is a long-term solution that can release phosphorus into soil for three to five years.

Problems From Excessive Phosphorus

As problematic as low phosphorus levels can be, an overabundance of this nutrient should also be avoided. Too much phosphorus in soil can make it difficult for plants to take up other nutrients, particularly iron and zinc, even if they are present. To lower phosphorus levels, first avoid using fertilizers that contain this nutrient. You can help plants absorb iron and zinc by applying a foliar iron and zinc solution. Foliar applications allow plants to absorb these nutrients through their leaves, rather than through the roots.