A new “smart” phosphorus fertilizer developed by Penn State horticultural scientists improves plant root growth, drought tolerance, shoot quality, and flowers, while also preventing up to 90 percent of the nutrient runoff that can foul waterways.
The new fertilizer is undergoing Pennsylvania field trials with the aid of a grant from the Commonwealth’s Department of Agriculture. However, field trials in Florida have been ongoing since 1998 and have shown high performance of ornamentals grown in sandy soils prone to leaching.

The fertilizer has also been shown to improve plant growth and drought tolerance while virtually eliminating leaching in nursery or greenhouse plants grown in peat or soilless media. In the soilless systems tested by the Penn State researchers with a wide variety of ornamental plants and vegetables, leaching was reduced to less than 1 percent of conventionally fertilized plants.

The new field fertilizer, which is being patented by the University, was developed by plant nutritionist Jonathan Lynch, postharvest physiologist Kathleen Brown, and research support associate Robert Snyder. The inventors say that the new fertilizer may be useful for stadium fields and golf courses as well as in agriculture and floriculture.

“In traditional fertilizer systems, the amount of nutrient available to the plant is large immediately after application and declines as the plant takes it up and the nutrient runs off when it rains,” Lynch says. “However, in the new ‘smart’ system, the supply of phosphorus available to the plant always matches a level typically found in ‘natural’ soils.”

In the new “smart” system, phosphorus is automatically released and maintained at low, natural levels by the chemical buffering action of aluminum oxide. The phosphorus is bound on the surface of aluminum oxide granules, which allows only a limited amount of the nutrient to be released. More of the bound phosphorus is released only as the initial amount is used up. The low levels of phosphorus released by the “smart” fertilizer mean that there is less to enter ground and surface waters.

Lynch notes that environmental regulations on runoff can be expected to become tighter in the near future. Sudden growths or blooms of microorganisms caused by nutrient runoff can cause life-threatening human illness and make rivers, streams, lakes, and beaches unattractive and unhealthy for wildlife. He adds that Europe already has tighter regulations than the United States.

While the low, natural levels of phosphorus released by the new “smart” fertilizer can play a role in improving the environment, growers and consumers can also benefit from improved plant quality. In experiments with marigold and impatiens grown in the greenhouse, plants that received the new “smart” fertilizer developed better root systems. High phosphorus levels created by traditional fertilizer systems discourage root growth. Better root systems enable the plant to be more drought-tolerant. Plants nourished with the “smart” fertilizer also had a slightly higher number of flowers, and the flowers wilted more slowly during drought.

“The buffered fertilizer system can also be recharged after most of the phosphorus on the aluminum oxide is gone,” says Lynch. “Using existing systems, a grower can add phosphoric acid and the buffer could be good for 20 to 25 years.”

The new fertilizer supplies only phosphorus, one of the three primary elements needed for plant growth. The researchers are beginning research programs to develop similar systems for nitrogen and potassium.

—Barbara Hale