A view from the West

Featuring food, fuel and the future in Jersey

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NPK. and two of them are a problem

Every gardener is aware of the three basic mineral requirements for plants  - nitrogen, phosphorus and potassium. They are usual refered to by ther chemical symbols NPK.   There are planty of other elements/minerals required in micro amounts for healthy plants too, but those are the big three.

Most people have some awareness of the problems of nitrogen in the form of nitrates and nitrites in drinking water (and processed food  especially cured meats).  Very few  are aware there is a problem with  phosphorus too. In fact the nitrogen and phosphorous cycles combined form one of the nine  limits of the safe operating space of the planetary boundaries approach  advocated by the Stockholm resilience centre.  On this model we have already crossed the boundary of what is safe on both the climate change and biodiversity loss metrics.  It is also thought we have crossed the nitrogen limit, but not yet the phosphorus one.  But that does not mean there is no problem with phosphorus.   See In essence too much nutrient causes problems (eutrophication) and in aquatic systems this leads to algal blooms.

Like nitrogen there is a natural flow that happens, but also an additional loading from highly soluble forms used in agriculture.  As it happens phosphorus in large scale accessible forms for  artificial fertilizer is in fairly short supply and there are estimates we might be out of practical  mining  quantities in 50 years.   It seems obvious we need to find ways to reduce usage and losses and to recover and recycle what we do use.  And that points back to farming and growing practices. In the old days guano (dried bird droppings) was much prized as a fertilizer as it had  all three of the basic elements in useful quantities.  Any got a colombier?

Did I forget to mention  excess phosphorus in water is also associated with rapid sea lettuce  growth.  Another reason to make sure we are on top of this locally.


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