Diluting Fertilizer

[rice paddie]

It seems that whenever I read any literature and/or posts about fertilizer, the recommendation is to dilute by 1/4 or 1/2 the recommended dosage. Can someone explain to me why this is good practice? I'm fairly new to this hobby and can't seem to wrap my brain around it - after all, if I'm using fertilizer specifically made for orchids shouldn't I just follow the directions on the product?

For example, if the instructions on the product say that I'm to use 1/4 tsp per gallon every time I water, should I still be diluting that further?

[tucker85]

If you're using a fertilizer specifically made for orchids then you can follow the instructions on the label. If you're using a general purpose fertilizer you should use 1/4 to 1/2 the strength. The old adage is weakly, weekly. In other words a weak solution once a week. Some growers give an even weaker solution every time they water. Orchid roots do not grow in rich soil full of nutrients like other jungle plants do. They grow with their roots attached to a tree or rock where they only get dilute nutrients washed down to them by the rains. You can experiment to see what strength will give you good growth without burning the roots. If the fertilizer is too strong the tips of the roots will turn brown. Leaf tips may also turn brown.

[WhiteRabbit]

I agree with tucker. I will add that some orchid fertilizers recommended dilution may be recommended (per the instructions) to be used once or twice a month. In that case you may wish to dilute more to use it every week (except fir the week you flush the media).

[cbuchman]

Try using FirstRay's Fert calculator.

Fertilizer Mixing Calculators

[rice paddie]

Thank you to everyone that responded - I appreciate the advice!

[Ray]

"1/4 to 1/2 strength" is meaningless. If you have a 20-20-20 and use it at half-strength, it is the same as using a 10-10-10.

The thing to do is 1) get a formula that provides enough of everything without excesses, 2) decide on a concentration you want to try, so you can see how well the plants do in your conditions, and experiment over the long term.

Personally, I recommend that for a typical in-home grower, 100 ppm N is a pretty good level, assuming it is applied at that strength every 1 or 2 weeks. You can use my calculators to find out the amount to mix up, or for simplicity, just divide 8 by the %N on the fertilizer label. The result is teaspoons per gallon to use.

In my 20-20-20 example, 8/20=0.4, so something in the neighborhood of 1/3-1/2 tsp/gal is fine.