Question for Al, container mixture recipe

recoil_rob(6)May 8, 2010

I'm putting my trees in bigger pots this weekend, I have 55gal drum that I'll cut down to about 30gal.

I was able to find 100% pine bark mulch, which is very small nuggets with shredded material. I have coarse perlite in lieu of granite , I have read that's OK and a weight saver. I will have Turface or another name brand but still the baked clay product. The mixture will 1-1-1.

I figure each container will take about 7-9 cubic feet of mixture.

How much dolomitic lime do I add to each container?

How much 3-1-2 fertilizer do I add to each container?

Finally, when I asked for 3-1-2 fertilizer they said the closest they had was 3-1-5. They said to find out the brand name of the 3-1-2 as it's probably a proprietary mixture.

Can you tell me the brand name of your 3-1-2 or will 3-1-5 be OK.

thanks, Rob

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tapla (mid-MI z5b-6a)

"How much dolomitic lime do I add to each container?

Add 1 tbsp/gallon or 1/2 cup per cu ft.

"How much 3-1-2 fertilizer do I add to each container?"

The soluble fertilizers are applied in solution (fertigation) after the plants are situated in their pots. It's best to withhold fertilizer for a short period if you're potting up cuttings or if you've bare-rooted a plant. There is no significant advantage in withholding fertilizer if you are potting up. How you should fertilize depends a great deal on your soil choice and your watering habits. If you water properly, to the point of total soil saturation and so water drains freely from the container, you can fertilize at half strength weekly or full strength every other week while the plant is growing robustly. Always withhold urea-based fertilizers when soil temperatures are "Finally, when I asked for 3-1-2 fertilizer they said the closest they had was 3-1-5. They said to find out the brand name of the 3-1-2 as it's probably a proprietary mixture.

I need to familiarize you with the difference between ratios and %s. A 3:1:2 RATIO could be any fertilizer that has 3 parts of N to every single part of P and to every 2 parts of K. When we speak about RATIOS, use a colon between the numbers and when we speak about %s, use a dash. Illustration: 24-8-16, 12-4-8, and 9-3-6 are all 3:1:2 ratio fertilizers.

You can find Miracle-Gro 24-8-16 granular soluble and 12-4-8 liquid almost everywhere at this time of the year. I prefer Dyna-Gro's Foliage-Pro 9-3-6 though (Prefer it even though it's not so easy to find. You would likely find it at a hydroponics shop/store or on the net); mainly because it contains all the essential elements in a favorable NPK ratio AND in a favorable ratio to each other. This is an important consideration in keeping the level of total dissolved solids and electrical conductivity of the soil solution at their lowest levels and still prevent nutritional deficiencies while offering the best opportunity for maximizing growth.

I hope that was helpful. Good luck, Rob.


    Bookmark   May 8, 2010 at 5:23PM
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Very helpful Al, thank you. I was aware 24-8-16, 12-4-8, and 9-3-6 are all 3:1:2 ratio fertilizers but could not find any of those locally. I still have a few questions if you'll indulge me.

1-Once I have a 3-1-2 fertilizer I understand that it is applied as you described above. But what if I get one with higher percentages such as a 24-8-16? How do I determine what strength to mix that at? Would I mix it with 8X the water to bring it down to 3-1-2?

2-I going to mix my soil with Pine Bark Mulch, Perlite and Turface3 at 1-1-1 by Volume. The mulch and Perlit come in 3cu. ft bags, no problem. But the Turface come in 50lb bags. What is the conversion factor for Turface from weight to cu. ft?



    Bookmark   May 9, 2010 at 11:43AM
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tapla (mid-MI z5b-6a)

Forget the 3:1:2 as percentages. It's simply the ratio illustrating the relative amounts of NPK in relation to each other. 24-8-16 and 12-4-8 are both the same ratio, but 24-8-16 has twice as much N,P,and K as the 12-4-8. The fertilizer manufacturer has a target TDS/EC in mind, which in the end means directions on the package will both yield the same strength solution, so use the directions as your guide. The 24-8-16 suggests you use a tbsp per gallon, and the 12-4-8 suggests 1/3 of a capful. The cap holds 5 tbsp, so 1/3 of a cap is about 1-2/3 tbsp or 5 tsp.

It's not that you need to worry about reducing the solution to 3%-1%-2%. If you planned to fertilize at half strength weekly, you would simply combine half of the suggested amount to make a full strength solution and fertilize with that solution. For the granular 24-8-16 you would use 1/2 tbsp, which is 1-1/2 tsp, and for the 12-4-8 liquid you would use 1/6 of a capful, which figures out to about 2-1/2 tsp or a skinny tbsp.

Another way of looking at it is once you are sure you have a 3:1:2 ratio, 3:1:2 never comes into play again. It's all about suggested dosages and how you want to adjust those dosages to suit your purposes.

I figured out what you get when you follow the suggested full doses:

24-8-16 (1 tbsp/gallon)
N **** 950 ppm
P **** 139 ppm
K **** 526 ppm
for a total of 1,615 ppm TDS (plus what's in your irrigation water)

12-4-8 (5 tsp/gallon)
N **** 792
P **** 116
K **** 438
for a total of 1,346 ppm TDS (plus what's in your water)

You can see the dosage is very close to the same level of TDS, with only 269 ppm separating them.

These doses are fine when the plant is growing well, but I like to keep TDS levels under 1,000 ppm (including what's in the water - for me, that's about 275-300 ppm TDS) because it makes it easier for the plant to absorb water and the nutrients dissolved in water, which is why I prefer to fertilize at 1/2 the recommended strength and at 1/2 the recommended interval. The plant gets the same amount of fertilizer, but there is no 'spike' in the level of TDS/EC - it's just better, though it requires a little extra effort.

Take care.


    Bookmark   May 9, 2010 at 3:24PM
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