Fertilizer Question

fortyonenorth · March 16, 2012

Quote:

Originally Posted by willyb

Too much N You will get too much folage at the loss of fruit. The right ratio is 2-6-3 or as close to that as you and get or make. It is good from seedlings to harvest. No need to change for fruiting.

What's of primary importance is that nutrients are available in the right proportions from the soil's perspective so as to minimize nutrient competition and antagonisms. The plant simply needs the necessary nutrients to be available at the appropriate times and in adequate amounts for each phase of growth.

I wonder if these "ideal" ratios are a legacy of the synthetic age, when fertilizers were applied in immediately available forms. In the organic world, applying 2-6-3 (or 2-1-3 or whatever) doesn't mean that a specific proportion of nutrients will be available to the plant at any given time. You have to look at the ingredients and application instructions (initial + subsequent dosing). Even then, nutrient availability is subject to any number of factors.

I'm not familiar with the ingredients in the Fox Farms product, but let's use it's NPK as an example. 7-4-5 may seem like a lot of N in proportion to PK. But, if the N is from a quickly available form, like blood meal, then it's going to provide a quick boost of N precisely when the plant needs it. By the time fruit has commenced, it will have tailed off to perhaps 30-40% of it's peak. P from rock phosphate will be more slowly available than P from bone meal. K, most commonly from potassium sulfate or K-Mag are both minerals and take some time to become available.

To complicate matters further one has to consider pre-existing substrate and environmental conditions, not to mention container substrate. Are you using a straight peat-lite mix? Or, a premium mix that's been fortified with forest humus, kelp meal, worm castings, bat guano, mycos etc. etc. If you're using mycos, you don't need as much P to get the same response.

So, just a long-winded way of saying that there's a lot that factors into the NPK equation, especially with regard to organic fertilizers.