Phosphorus Roles in Plant Health

May 15, 2023

Phosphorus is considered the energy mineral and a deficiency of it will significantly reduce yield, due to being involved in the energy production and transfer process called ATP, adenosine triphosphate.

When calcium & phosphorus levels are adequate, it is easier to absorb and keep all other minerals in the plant.

As we could expect from an energy mineral, phosphorus promotes earlier maturity in crops. We are used to hearing maturity dates, like 90 day corn, 70 day peppers, etc. but the reality is that crop maturity is based on energy, not directly on days. And while there are many minerals that influence energy, phosphorus has the most direct correlation because it also has to transfer the energy once it is produced. So even if enough energy is produced, a deficiency of phosphorus is like running an engine without the clutch in gear. In other words, all the energy you can produce won’t help you anything unless it is transferred into usable energy. And it takes phosphorus to do that.

In addition to energy transfer, phosphorus is also involved in sugar metabolism; in transforming the simple sugar produced during the photosynthesis process to a more advanced complete sugar that improves insect and disease prevention. It also helps protein metabolism, making sure that the proteins being produced are complete proteins without nitrate and other forms of soluble proteins.

Another interesting point is that we have noticed with the help of sap analysis is that potassium levels tend to correlate somewhat to phosphorus levels, which may mean that the phosphorus is somehow influencing potassium uptake, which is entirely logical because plants need energy to pick up nutrients and water. Also, phosphorus activates enzymes that are directly involved in fruit ripening.

Several other interesting points: Phosphorus helps tillering and consequently the number of heads (panicles) in cereal crops, it speeds up cell division, and very importantly, in involved in building the phospholipid layer that is part of every healthy cell membrane. These phospholipids help protect the plants from disease attack. Phosphorus is also a reproductive nutrient, which means that it has a substantial impact on the number of buds and fruit that the plant is capable of producing.

The visual deficiencies of phosphorus are stunted growth. If the deficiency is bad enough, the leaves will turn red or purple, especially in the oldest more mature leaves, because the simple sugars are not being metabolized and are building up within the plant structure.

What can be done to promote adequate levels of phosphorus? Phosphorus is a biological mineral, meaning that the uptake of phosphorus is largely driven by soil biology. In particular, mycorrhizal fungi has a substantial impact, as does anything that helps root development, such as boron, which may increase the uptake of phosphorus and other minerals by as much as 50% because of its impact on root development. Phosphorus is considered immobile in the soil, which means that we need larger roots to absorb more phosphorus.

Spring phosphorus deficiencies are especially common because cold soil reduces phosphorus availability.

Magnesium helps activate phosphorus as does zinc. Both can effectively foliar sprayed to get a response. Or if liquid phosphorus is applied directly, it should be from a plant derived source or complexed with carbon. Otherwise, the phosphorus may serve to only make the plants lazy and reduce its need to produce large roots.