Allotment Gardening Advice Help Chat
Growing => Grow Your Own => Topic started by: Grubbypaws on September 02, 2022, 10:33
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This subject came up on one of the other posts. After I posted I have always used Chempak low nitrogen food which I have just taken at face value (Low nitrogen). Checking their website today I see that it has a N:P:K ratio 12.5:25:25 which is a low nitrogen ratio but still quite a lot of nitrogen Tomorite has an N:P:K ratio of 4:3:8. Interestingly Chempaks specialised slow release potato feeder has a ratio of N:P:K - 4-6-12 +4MgO I realised that I didn't understand it well enough and started reading. So here is what I have found
An N:P:K ratio of 12.5:25:25 means it has 12.5% Nitrogen, 25% Phosphorus, 25% Potassium and 37.5% other. So 62.5% is fertilizer.
A ratio of 4:3:8 (tomorite) has 4% N, 3% P, 8% K and 85% other which in a liquid feed means water!
So the advice I have found is "The most important thing when buying fertilizer is to buy the correct ratio so that you get the correct relative amounts of nutrients. In general, a fertilizer with higher numbers is cheaper as you need to use less. Many of the liquid fertilizers on the market are very dilute and they are also some of the most expensive fertilizers you can buy. From a price point of view, always buy the one with the higher numbers provided it has the correct ratio".