# How does N-P-K effect each other?



## LawnDetail (Apr 15, 2020)

Is there optimal levels of NPK to make each other perform well? Does a deficiency or a high level of a certain nutrient prevent the uptake of another?


----------



## Virginiagal (Apr 24, 2017)

The more growth, which is driven by nitrogen, the more phosphorus and potassium needed. A deficit of phosphorus and potassium can have detrimental effects. An excess of phosphorus and potassium is just not used. It may be lost by leaching or stick around in the soil. Here's an article of interest on the topic:
https://turf.unl.edu/NebGuides/Ideal-Fertilizer-Ratio.pdf


----------



## Phids (Sep 24, 2020)

Virginiagal said:


> The more growth, which is driven by nitrogen, the more phosphorus and potassium needed. A deficit of phosphorus and potassium can have detrimental effects. An excess of phosphorus and potassium is just not used. It may be lost by leaching or stick around in the soil. Here's an article of interest on the topic:
> https://turf.unl.edu/NebGuides/Ideal-Fertilizer-Ratio.pdf


I would like to add to the conversation that even if the lawn does not use the excess of phosphorus, it can still be quite harmful by decreasing plants' ability to absorb certain key micronutrients (iron, zinc, manganese), it can reduce beneficial mycorrhizae in the soil, and it can contaminate runoff and create problems for fish. In other words, phosphorus application still needs to be limited, especially since it can take a long time for levels to be return to normal if too much has been applied.

https://agrilifelearn.tamu.edu/s/product/phosphorustoo-much-and-plants-may-suffer/01t4x000004OUgi


----------



## Virginiagal (Apr 24, 2017)

I agree with @Phids. Too much phosphorus is a problem. Because of environmental concerns a number of states and localities prohibit phosphorus unless a soil test shows a deficiency or you're seeding. Most general fertilizer blends marketed to homeowners have nitrogen and some potassium but no phosphorus. It's best to fertilize according to your soil test results and its recommendations.


----------



## Virginiagal (Apr 24, 2017)

Phosphorus tends to get bound up with other elements in a high pH soil and then is unavailable to the plant. So if you're getting repeated recommendations for phosphorus and you have high pH, the phosphorus you have been putting down is still there but the grass can't use it. Rather frustrating. Potassium tends to leach away in low CEC soil. So if you have low CEC and you get repeated recommendations for potassium and you wonder what happened to all the potassium you have been putting down, it's likely to have leached away. In that case spoonfeeding is best. Back to @LawnDetail's question, it's the grass itself that draws out what it needs. Nitrogen spurs growth and with more growth is more demand for phosphorus and potassium. Potassium is a cation. Phosphorus is an anion. They don't compete against each other.


----------



## g-man (Jun 15, 2017)

The ratio of usage is for every pound of nitrogen, 0.5lb of K and 0.125lb of P are used. If you mulch mow, most of the K and P would be returned to the soil once the clippings decompose.


----------



## Ridgerunner (May 16, 2017)

LawnDetail said:


> Is there optimal levels of NPK to make each other perform well? Does a deficiency or a high level of a certain nutrient prevent the uptake of another?


That is a really loaded question with no simple answer. With regards to the NPK question: see g-man's reply. However, there are 16 "known" nutrients required for good plant performance and excesses of NPK can affect the uptake of those : see Virginiagal's and Phids replies for a couple of the many reasons excesses can affect uptake of other nutrients. For a primer course Google Muldar's Chart.


----------



## LawnDetail (Apr 15, 2020)

Thank you everyone for your input in answering my question. It was exactly what I was looking for and then some.


----------

