fertilizer

[63pmp]

The major elements absorbed by plants (N,P,K,P,Mg, etc) are always taken up by the plant in the form of mineral salts. All fertilizers contain salts. That is why it is important to know the salt tolerance of your plants.

Manutec bloom booster is a blend of mineral salts, eg ammonium nitrate, potassium sulphate, diammonium phosphate etc. Mineral fertilizers such as bloom booster or aqausol will be low in sodium (though will be present as a contaminant, that is why it is not listed in the analysis). The main problem with mineral fertilisers is that they often lack calcium and magnesium. I don't think they are appropriate as an everyday feed for pot plants, rather they are intended as an extra feed for plants in the ground, or foliage feeds.

Working out value for money is really difficult, for example organic fertilisers like dynamic lifter have lower NPK content, yet there are extra benefits from the organic matter they provide in that it provides nutrient buffering (ie nutrients hang around longer), and cation exchange capacity. Mineral fertilisers will provide more plant available nutrient when applied, but will also leach out quickly. There are benefits of using both. The best value for money are agricultural fertilizers, but you have to know how to blend them. For example a 40kg bag of di-ammonium phosphate is about $40, this has an NPK of 17.5:20:0. A 2kg pack of thrive is just over $20 for comparison.

Fertilizing gets very complicated very quickly. For instance, excess potassium will prevent the uptake of calcium by the plants, causing calcium deficiencies, even though there is sufficient in the soil.

To make life simpler we can make the assumption that bonsai culture is a form of hydroponics, (especially if you use inorganic potting mixes) then we can look at the fertilizer ratios already developed for drip irrigation /fertigation practices and use them as a guide. This is a guide showing the range of nutrients for hydroponic solutions. The important thing is the various ratios of elements to each other. Concentrations vary according to salt tolerance of plants, but ratios remain the same.



N 70-200 NO3 0-31 NH4
P 15-60
K 200-400
Ca 150 – 300
Mg 25-60
SO4 20-150
Fe 0.5-14
Mn 0.2-1.0
Zn 0.04-0.2
Cu 0.02-0.1
B 0.2-0.5
Mo 0.03-0.08


Paul

[63pmp]

I forgot to mention that all values are in ppm. For conversion of % to ppm; 1gram of anything dissolved in 1litre of water is 1000ppm. 1% of a kilogram is 10grams = 10 000ppm so when a fertilizer says it has an NPK of 10:10:10, it contains 10% N 10%P 10%K

Paul

[Bretts]

So 1ppm = how much % ?

I will try to understand the rest later thanks

[Jarrod]

0.0001%

[63pmp]

Doesn't quite work that way. What NPK ratio does is let you calculate how much of each element you are adding to plant, paddock etc.

For example, Thrive has NPK of 15:4:26. 1/4 teaspoon of Thrive weighs close to 4g, therefore amount of N is 15% of 4 grams = 0.6 grams. Dissolve 4 grams thrive in 1litre of water the concentration of N is 0.6x1000/1litre = 600ppm. Dissolve this in 9 litres of water (typical watering can) concentration is 600ppm/9 = 67ppm.

Dynamic lifter is 4% N, so add 100g of DL to your pot, you're adding 4g of N. If the pot contains 5 kilograms of potting mix, then the concentration of N added is 4/5 grams/kg, or 80O ppm. A good thing it's slow release!

Paul

[Bretts]

ok But if I am comparing ppm to % on the analysys is 0.0001%= 1ppm ?
I worked this out once through a google converter but can't be sure I am doing the figures right with your numbers?

[63pmp]

Yes, but only if they are reporting in mg/kg, or mg/l, on the analysis.

% and ppm are old terms and can be misleading. Better to stick to SI units.

Paul

[Bougy Fan]

Has anyone tried Searles Robust Plus Native Plant Food instead of Osmocote ? I have only looked online and see it comes in a 25 kg bag. I was wondering if that would work out cheaper ? Has anyone used it - is it granules the same as Osmocote ?

Tony

[Bougy Fan]

Anyone out there ?