Good source of general purpose slow release (>4 month) fertilizer like Osmocote?


Dynamite has calcium but is missing zinc.

Osmocote Plus has Zn but is missing Ca.

However, the lime in most mixes adds Ca to my understanding, and pine bark (a component of most mixes) provides some zinc.


Yeah I make my own soil mixes and would never add lime. It makes the mix way too basic especially if you use tap water which will supply plenty of calcium. Many fig growers use it, and I myself think it is a huge mistake. My mix has 3 parts pine bark, all other additives are 1 part of less, so zinc is probably good. I also use Foliage Pro and many organic fertilizers on all my plants.


Since I spent a bunch of time making it, I figured I would share the spreadsheet I made comparing different slow release fertilizers. Let me know if you want me to compare any others.

Here is a preview:


Yeah using them for containers mostly and at 1/2 rate for vegetable raised beds top dressing in addition to compost. If I do use it on my in-ground trees I use it at 1/2 rate and only at the very start of the growing season.

By the way, some formulations I see use 6.6% Ammoniacal Nitrogen, 5.7% Nitrate Nitrogen and 6.7% Urea Nitrogen while others use 9.60% Ammoniacal Nitrogen and 8.40% Nitrate Nitrogen. What are the pros and cons of both in terms of use for growing vegetables, potted fruit trees and strawberries?


Urea and Ammonium acidify the soil to a degree- enough to be significant over time. They also stick around longer- bond a bit with the soil while nitrate can be quickly washed away, so in wet conditions (as is often in early spring) there is an advantage to this.

I’ve often read that nitrate is not good for blueberries- and beyond the acid issue- can’t remember the specifics off the top of my head- someone will likely chime in who knows.

Urea is the least expensive form of N besides anhydrous ammonia, which is great stuff for making bombs so farmers have to be careful about protecting it. It is not generally available to the general public.