Peters 20-20-20 + TE Professional

[Blueszz]

Originally Posted by camille1585

I'm following both Ray and Akerne's advice, which happen to come out to roughly the same thing. Ray suggests 100ppm N per week, and I usually water twice a week most of the year so that's 50pp per watering. Akerne's dosage (works out to 60ppm N) is because according to them it is sufficient for the majority of orchids, and no periodic flushing of the substrate is required at that dosage.

Your dosage is still fine (was sort of the 'standard' when I started on OB) but you might need to flush with tapwater every 4-5 waterings.

Ah, I didn't take watering twice a week into account. And I didn't think of the 100 ppm a week.

I now understand why you dose lower. Thank you for explanation.

Currently I water about once a week when a plant needs it. And I have a habit to flush media every now and then (no schedule) after "soaking" it for a while to dissolve as much minerals as possible.

[Intruder]

There are two other Peters fertilizers more suited to orchids cultivation.
Peters 21-7-21 3MgO and Peters CalMag these two fertilizers, like the 20-20-20, are very acidic. Where I live, the city water is very hard (35°F), which is equivalent to 350 mgr of calcium carbonate per liter. To prepare a solution with 50 ppm nitrogen, I have to add at least 10% of this tap water (volume) to the rainwater so that the solution has a pH of around 6. Apart from Akerne's RainMix, there's no fertilizer that's well-suited to orchid cultivation, and even for this one I have to check the pH of the final solution, so I add a few drops of 1M KOH.

[Fairorchids]

Originally Posted by estación seca

Do not water before fertilizing. Proper concentrations of fertilizer will not harm roots. Watering first fills up velamen with plain water, and less fertilizer will be absorbed. Fertilizer applied after a plain watering is mostly wasted.

TDS meters don't measure total dissolved solids. They measure electrical conductivity, proportional to the number of charged particles in the solution. Unless you know exactly which chemicals are in the solution these meters don't yield useful data. Total dissolved solids are measured by evaporating a known quantity of water and weighing the minerals left behind. There aren't any meters that can do this.

Your water company publishes an annual water quality report. It will tell you what is in your water. It may report total dissolved solids, water hardness, or give amounts of each chemical species present. You can add the amount of fertilizer you plan to use and calculate TDS for yourself.

It is not often I disagree with postings from ES, but here I do.

From a commercial view point, we all water first, and then apply a light dose of fertilizer second to the freshly watered plants.

Why? Because we pour water on during watering, probably 10-20 times as much, as we do during the fertilizer application. If the plants are too dry when we start, we water each plant 2 or 3 times to get it fully saturated before we apply the fertilizer.

Yes, you could use Peters 20:20:20 at 75-100 ppm, but by the time you are done watering, you are still using 10 times as much as I do at 300 ppm in a light dose every 2 weeks.

[estación seca]

I've been told not to water before fertilizing by two agriculture professors and several commercial orchid growers. Fred Clarke of Sunset Valley Orchids spoke to our society last week and said not to water first. I'm working on my notes from the talk and will eventually post them. Fred said he never waters with plain water. Every watering contains fertilizer.

[rbarata]

Originally Posted by estación seca

Fred said he never waters with plain water. Every watering contains fertilizer.

My watering scheme tends to be like this, except on a few picky species.

[Fairorchids]

I know that some people use fertilizer in every watering, but at a much lower concentration - and for plants growing in a mix of their choice.

All the commercial growers I have discussed this with water first.

Pouring dilute fertilizer into a pot for 10-20 seconds is an awful waste (compared with watering first, and then applying a small volume of 300 ppm at the end).

[Ray]

For large-scale growers, I certainly can see the accommodation for economy, although the labor cost of watering twice makes me wonder just how cost effective that is.

Back when I was watering my plants with a 25 ppm N solution, I typically used ~50 gallons at a time, resulting in a net cost to me (at today's retail price for K-Lite) of about $1.00.

[Fairorchids]

It takes us 2.1/2 to 3.1/2 hours to water the whole greenhouse (26 x 96), depending upon how dry the plants are.

We then apply fertilizer with a hose end sprayer, which takes 40-45 min (since we have to refill the sprayer with concentrate 12-15 times).

With a smaller collection in your house or hobby size greenhouse, where you only provide a few ounces to each plant, i can see the 50-100 ppm solution in every 'watering' making sense. However, I am always concerned about salt build-up in the pot, so I insist on at least one watering with clean water between each fertilizer application.

[Ray]

But if you don't let the medium dry out, there is little to no precipitation.

[Fairorchids]

True, but with my crazy schedule (and assorted snow storms), I do not always manage to water on a regular schedule. This past week, I intended to water on Tuesday, but the snow storm prevented that. On Wednesday I had to drive 300 miles making deliveries for Valentines Day, Thursday was prep & set-up for the Deep Cut OS Show, and I was selling in the show Friday, Saturday & Sunday.

When I finally watered today, it was 11 days past the previous watering.