How To Make Your Own
Slow-Release Fertilizer Cakes
by
Dale Cochoy
During an April trip to Washington ,D.C. for the Potomac Bonsai Show, my friend Bob Stevens and I talked for several hours on our CB radios as we drove along in separate cars. One subject we covered was the prospect of getting together and making some slow-release fertilizer balls. All experienced bonsai growers agree that the best method of fertilizing bonsai is with a slow-release type of fertilizer ball or pellet. These will release a constant low-dose of fertilizer with each watering or rain. This constant but slow-release of nutrients keeps your trees healthy and steadily growing instead of the shot-in-the-arm type of strong fertilizing that is done from time to time during the growing season. These occasional doses of fertilizer can cause your bonsai to grow out of control ---like a weed.
Slow-release organic fertilizers can be very expensive. Even the rapeseed cakes from China or Japan can be quite costly as well as the more commonly available marketed brand names.
We purchased the ingredients to produce our own slow-release fertilizer balls that we thought would be better than some mixtures we had seen in magazines or heard about elsewhere.
The ingredients comprising approximately 65% of the bulk were bone meal and cotton seed meal. These can be purchased easily in 3lb. or larger bags. We used 20% gypsum as an experiment to help release possible salt build-up in the haydite used in our potting soil mixes. Blood meal made up about 10% of the bulk of the dry mix. For the liquid we used a couple of things. We mixed in some "Alaska Start-Up"tm low dose natural fertilizer made from molasses, this also contains B-1 vitamins. A small amount of "Superthrive"tm was used. We poured in a considerable amount of fish emulsion. If you are unfamiliar with this product, it is quite possibly the most disgusting substance on the face of the earth!
We, by no means, measured anything. We added bulk and liquid to use up most of the materials and keep the mixture moist enough to form balls. For about $25 we mixed up roughly 71/2 gallons of the foulest smelling stuff you can imagine!
It formed balls but they didn't stick together well. After mulling over several possible additives that might help adhere the concoction, my wife, Nancy, came up with the solution. I mixed in about 3 cups of flour per gallon.
It is a good idea to wear some hospital rubber gloves for the mixing involved in fertilizer ball manufacturing. With the binding problem solved it was time to form the mixture into balls. I found that two people could process a gallon of the mixture into about 250 balls 2/3 the size of a golf ball, in about 1/2 hr. We just rolled the mixture in the palm of our hands. Those of you with experience in diaper changing will feel right at home, as there are some similarities here! I found that with my half of our mixture I could make about 800 balls in a few hours, at a cost of about $15.
Since our original attempts I have made some changes in manufacturing and mixture. I no longer form them into balls by hand. A wheelbarrow full will leave you crippled without enough grip strength to hold a beer can. After trying several different methods of extruding, I found that a simple tool made from about 18 inches of 1inch or 11/4 inch PVC pipe with a corresponding sized wooden dowel to push through the pipe worked OK but a better, simpler method of forming cakes was adapted.
I now mix up the disgusting muck in a wheelbarrow then I press it into old hospital food trays( cookie sheets or pizza pans work well ) about 1/2" deep. The trays should first by lined with Saran wrap to allow release of the cakes from the pan while still moist.
After one day of drying in the hot sun I can cut it into 1 or 11/2' squares using a pizza cutter. The sheet of cakes takes longer to dry than the balls, but can be made in a fraction of the time. I simply flip them over into another tray once a day until dry. They easily break apart when dry. As I stated, I mix up a wheelbarrow at a time. The best method for doing this is to first mix all the dry materials together except for the flour. Mix any amount you want. Combine all your liquid ingredients in a sprinkling can with some water and slowly pour in while mixing with a shovel. It is very much like mixing cement. I slowly add liquid and flour to get just the right consistency. I use about 10lbs of flour per wheel barrow.
I mentioned that I made some changes in the mixture. I no longer add "Superthrive"tm. Although it is great stuff and I use it to soak and water collected material, it is a little too costly for this use. I now add liquid seaweed to the mix, liquid chelated iron, and muriate of potash to assist in strengthening roots and aid in absorption of nitrogen and phosphorus, and to increase resistance to heat and cold. I only use about 2 cups of muriate of potash to a wheelbarrow.
I worried about the attraction of flies and maggots so I thought of spraying the finished cakes with an insecticide but I found that my dogs find the cakes an exquisite snack and they disappear often from pots that are low to the ground. Luckily I have had no problem with flies.
The ingredients I use are as follows:
Bone meal 0-10-0
Cotton seed meal 6-1-1
Blood meal 12-0-0
Fish emulsion 5-1-1
Liquid seaweed 0.1-0.0-1.0
Alaska Natural start-up 2-1-2 w/B-1
Muriate of potash 0-0-60
Gypsum
Liquid chelated iron
Flour
The mixture has to be experimented with as you work to get the consistency right. I can make over 1,000 cakes for under $30 worth of ingredients and an afternoon of time. I believe this mixture is far superior to anything imported into this country, and cheaper in bulk. They will not burn trees or retard mycorrhiza growth so you can place as many as you want on the surface of your pots. I put two on a 6" pot, four on an 8-10", and more on larger pots. Replace as they start to disintegrate.