UK and ROI ferilizer declaration

Protein · Posted: Mon Mar 29, 2010 10:00 pm Post subject: UK and ROI ferilizer declaration

I bought a tub of Miracle-Gro and noticed they have two declarations of the NPK values

UK NPK values 24-8-16
ROI NPK values - 24-3.5-13.3

Question is, why is there a need to have two systems of declaration and why is there such a vast difference between both systems?

Regards
Me

michael brenock · Posted: Wed Mar 31, 2010 6:27 pm Post subject:

the U.K. and R.o.I. use different standards for P and K. Here in ireland we use the pure element for P and K whereas in U.K, they use P2O5 (Phosphorus Pentoxide) and K2O (Potash). I hope I have got this right as it is about 50 years ago I learned this.
michael brenock horticultural advisor (retired)

Protein · Posted: Wed Mar 31, 2010 7:56 pm Post subject:

Hi Michael, that sounds interesting, so penny for penny, the UK get less P and K than stated.

I have subsequently found information on the Defra website, but I was left more confused and just as clueless

http://www.defra.gov.uk/foodfarm/landmanage/land-soil/nutrient/fert/reg.htm

Me

michael brenock · Posted: Thu Apr 01, 2010 8:53 am Post subject:

they all get the same amount. The plant roots take in phosphorus as phosphorus pentoxide P2O5 not as pure P similarly potassium is taken in as potash K2O not as the element K . Phosphates and potash occur in compost heaps but must be converted to the form which the plant roots can take in when it is in solution in the soil.
Don't be too worried about this the plants are wonderful to be able to perform this miracle.
michael brenock horticultural advisor (retired)