Fertilizers make me confused!!!

[mimigirl]

I am currently using Better Gro granular 20-14-13. I am using it half strength. I want to change to a liquid. Here are my questions:
1. If i change to a 7-9-5 can i use it full strength since it is not as strong as 20-14-13 is when i half it?
2. MSU is 13-3-15. Would i need to half the strength?
3. What are some of the ones you all use and is it at half strength or full strength?
The more articles I read the more my head spins!

[Orchid Whisperer]

I'm not sure why you would change to a liquid unless you like paying for water (?) The water soluble solid fertilizers are a better bargain, IMO.

If you want to be precise about things, Ray Barkalow has on his website a fertilizer TDS calculator Fertilizer TDS Calculator - First Rays LLC and an explanation of TDS and fertilizer TDS & EC - First Rays LLC You can shoot for Ray's target of 100 to 125 ppm of N as estimated by his calculator.

Most orchids are weak feeders. You don't mention what you are growing, but for the types most commonly grown by beginning and intermediate growers (Phalaenopsis, Cattleya types, Oncidium types, etc) you can go with a more simplistic approach and just provide fertilizer at 1/4 to 1/8 the strength recommended on the package and your orchids will grow just fine.

Regarding the 3 numbers representing N-P-K, When growing, most plants require more N and K (about equal) and less P. Your 20-14-13 is a higher N fertilizer, and is more of a growth formula. A 7-9-5 has N and K lowered relative to P and the lower N should help the plant perform better when it is ready to bloom.

Some fertilizers contain calcium and trace elements (micronutrients). If your water is low in mineral content, fertilizers containing micronutrients are beneficial. Your local water utility probably measures and can tell you the concentrations of Ca, Mg, and other elements, as well as total dissolved solids content.

If you'd prefer something that is closest to a one-size fits-all solution, find a fertilizer close to a balanced fertilizer (all 3 numbers equal, or at least close), perhaps with micronutrients, use at 1/4 to 1/8 strength once or twice a month.

A good source of not-too-complex fertilizer information is at Orchid, Water Quality, Fertilizer, pH Management, Nutrition

[jason45244]

I like to use Jacks 30-10-10 while my plants are in the growth phase, And Jacks 3-9-6 when in spike/sheath for blooms even though some folks disagree with that, it works for me.

[bil]

There are a myriad diifferent fertilisers out there, and all swear they wiill love you forever, etc etc etc.

Turn that on its head and look instead at what they would get in the wild. It isn't a lot.

Ray came up with the idea of analysing the runoff water, and seeing what was actually available to epiphytes. He reckons that they LOVE potassium, because it is so scarce, and they lack the mechanism to stop taking it up when they have enough.

I use his fertiliser with RO water and at a very low level. between 25 and 30 ppm and I use that mix for every watering they get. So far the results have been pretty good.

[jason45244]

Originally Posted by bil

There are a myriad diifferent fertilisers out there, and all swear they wiill love you forever, etc etc etc.

Turn that on its head and look instead at what they would get in the wild. It isn't a lot.

Ray came up with the idea of analysing the runoff water, and seeing what was actually available to epiphytes. He reckons that they LOVE potassium, because it is so scarce, and they lack the mechanism to stop taking it up when they have enough.

I use his fertiliser with RO water and at a very low level. between 25 and 30 ppm and I use that mix for every watering they get. So far the results have been pretty good.

I've been thinking about switching to Ray's, but everything I know tells me not to because my plants are happy.

[Orchid Whisperer]

A bit of caution regarding the low K fertilizers. I've read posts on various forums where long-term users of the low K fertilizers report various problems. Do your own research looking for this info, decide before you buy.

Pretty much any plant in cultivation gets better mineral nutrition than an equivalent wild plant

As Jason said why change when your plants are happy. Bil, this applies if you are happy with the low K stuff too.

[bil]

Originally Posted by Orchid Whisperer

A bit of caution regarding the low K fertilizers. I've read posts on various forums where long-term users of the low K fertilizers report various problems. Do your own research looking for this info, decide before you buy.

Pretty much any plant in cultivation gets better mineral nutrition than an equivalent wild plant

As Jason said why change when your plants are happy. Bil, this applies if you are happy with the low K stuff too.

If it's stupid, but it works, then it isn't stupid.

What sort of problems were they experiencing?

[Orchid Whisperer]

Hi bil

I'm not saying K-lite, or its use, is stupid. In fact, I said if you are happy with it, why change.

I'll post a link to just one thread as a starting point, there are some opinions early in the thread regarding symptoms attributed to low K fertilizer. [url]http://www.slippertalk.com/forum/showthread.php?t=37714&highlight=K-lite[/URL . Fair warning, some of the opinions in the thread were argumentative, on both sides of the issue. Read if you care to, make your own conclusions.

What I would like to see is a true, controlled scientific experiment (a trial) that evaluates K-lite vs. other fertilizers. The only study I have seen that comes close was a study of potted Dendrobiums that varied the amount of the 3 major plant nutrients one at a time. Lower K produced lower flower number. I don't think any of the fertilizers qualified as true K-lite, though.

[Ray]

First of all, let me say that it was not my idea to analyze tropical forest "throughfall" to aid in the design of a fertilizer. K-Lite originated through the joint effort of a biological toxicologist working on freshwater mussels, and someone with a ceramics background (me) who has seen how K can preferentially occupy sites within glass and ceramic structures. It was actually later that analyses were shown to, for the most part, back up the conclusion that potassium is not in much demand by orchids, and that an excess could, in some circumstances, be potentially harmful.

I have been using it exclusively on my plants for just shy of four years, and am using it at a very low dose (about 25 ppm N), and my plants have never grown or bloomed better.

My personal assessment about fertilizers in general is that pretty much any formula may be used, but the demand for nutrition in orchids is so low, that keeping the application rate very low is more important than the formula itself.

90% – 95% of an orchid is water. More than half of the remaining (dry) mass is carbon. The next most abundant element in the plant is nitrogen. Potassium, phosphorus, calcium, magnesium, and sulfur are in the next tier, coming in at less than 10% of the nitrogen content. All the other mineral elements are at ppm levels.

I think where people get into trouble with feeding is in two areas, both as a result of overuse. Excessive nitrogen application will give great growth, and bright emerald green foliage, but the plants can be leggy, and blooming may stop altogether. The second is simply the buildup of high levels of minerals in the plant and especially in the potting medium, which can be toxic.

Folks often mistakenly assume that it's the fertilizer formula responsible for over application of nitrogen. It's not. 30-10-10 is often called a "high nitrogen fertilizer", with a 3-1-1 ratio. K-Lite is not known that way, even though its ratio is 12-1-1. The key is not the formula, but the amount used per gallon, and frequency of application.

Addressing another comment above, the "125 ppm N" target level for fertilizing was – again – not my idea. When the folks at Michigan State were testing their fertilizer formulas, they found that to be a reasonable level for infrequent feeding.

[tucker85]

If you're talking about Dyna-Gro 7-9-5, that's a very good fertilizer for orchids. I've used it in the past and I have several friends who still use it. The nitrogen in Dyna-Gro is in the form of nitrate and ammonium, which is exactly what you want. There's no urea in it. It also contains all three secondary nutrients, calcium, magnesium and sulfur. Some fertilizers leave the secondary nutrients out and orchids do need them. I'm pretty sure the bottle recommends 1/2 teaspoon per gallon which is a little less than 50 ppm nitrogen. I think I would use that amount most of the year. In the middle of the summer, if your orchids are growing rapidly, you could give a full teaspoon per gallon which would be right around 100 ppm nitrogen.