Q: Where is the P (phosphorus)?

The middle number on bags of lawn fertilizer seems to be disappearing.

Why is that?

Well, in addition to being one of the primary macro-nutrients needed to grow turf grass and most other plants, phosphorous (P) can be very harmful as a pollutant to surface waters. Phosphorous has very low downward mobility in soil and this low soil mobility can be further complicated by fine textured, heavy soils like clay (Richmond clay).

phosphorus for gardensSince we typically apply our lawn fertilizers to the grass surface several times per year the phosphorous(P) portion of the fertilizer will tend to sit on the soil surface for long periods of time.

Heavy rains can cause runoff of soils and thus phosphorous into rivers and lakes. This increased phosphorous(P) concentration in surface water environments leads to a process called eutrophication, which causes excessive algae blooms. The algae absorbs the dissolved oxygen in the water, leading to less oxygen for aquatic organisms such as fish, crustaceans and water born insects. Entire freshwater ecosystem collapses have been attributed to high phosphorous loadings due to run-off.

Most soils in our region have an abundance of phosphorous in them but much may not be available/plant usable. Soil testing annually is thus vital to measure N-P-K levels as well as soil pH. The simplest method to free up unavailable phosphorous (P) in turf soils is to add organic matter in the form of a high quality compost top dressing soil.

soil mixturesOrganic matter gets soil microbes working and creating reactions within the soil. One reaction or chain can be microbes using ATP (adenosine triphosphate) as an energy source and cycling the phosphorous into a more readily available form for plant uptake.

An integral part of our organic lawn care program is top-dressing with compost, top dressing soil or composted topdressing pellets based on your soil composition and soil testing results to ensure that your lawn has sufficient and usable N-P-K as well as an appropriate soil pH level.

All our lawn care programs are based on individual site specific scientific measures to ensure professional best management practices for environmental integrity and harmony.

Request a Quote »