Apply the Amendments

Before applying the amendments…

Decide what you are going to apply.

The first time you mineralize, we recommend that you apply 10 lbs/1000 sq ft (10 kg/1000 sq m) Azomite or Kelp for trace minerals. In a large area, apply what you can afford. Quantities can be reduced in subsequent years. Or, you may substitute foliar feeding with liquid kelp when the leaf stomata are open (usually in the early morning), about every 2 weeks through the growing season. The idea is to make a large initial application of all the trace minerals we don’t test for. We use kelp as a foliar fertilizer after the initial application and make sure to apply it when the humidity is high. High humidity favors foliar absorption.

It is best to add the recommended ag lime in the fall, and then add the other minerals in the spring. If this is not possible, all the minerals can be mixed together and applied at the same time.

Blend all minerals with compost before applying, if possible. We especially recommend mixing phosphorus sources (rock phosphate and bone meal) and manganese with vermicompost or a well-made active compost. The phosphorus sources especially need a bioactive soil in order to be available to plants. 

Composted manure is a good source of phosphorus, potash, carbon, and sodium. It is a great substitute for rock phosphate and potassium sulfate, if your soil can stand the sodium usually accompanying manures. Compost is highly bio-active, and will provide a biological path for phosphorus assimilation when the ionic path is closed by high pH. Studies at Colorado State University show rock phosphate is ineffective at high pH, but manure and manure based compost are effective. And (or), a high P fish fertilizer may be an effective source of phosphorus in a high pH soil. Rock phosphate and bonemeal are especially unavailable to the plants if the pH is over 7.5. Instead, use composted manure, or mix rock phosphate or bonemeal or bone char into an active compost pile, then dig in the finished compost.

Unless your compost is tested for mineral levels (such a test costs in the $150 range), you won’t know how much to apply for P&K deficits. Make an educated guess (there are default values in OrganiCalc), and maybe spread a layer 1/4 to 1 inch thick, then re-test next year to see the compost’s contribution to phosphorus and potassium. We imagine that everyone will apply compost as it is available, and have set the mineral target levels low enough that repeated compost applications will not be a problem.

Applying the amendments…

I usually apply minerals one at a time to my 2700 sq ft garden. This is not very time-efficient, but I like to be sure the minerals are evenly distributed. I weigh out the quantities for the area I am fertilizing, and cast the minerals onto the beds. If you use overhead water or are blessed with rain during the growing season, you may want to fertilize the paths too, so the roots can find sustenance there. If you periodically remake the beds in different locations, fertilize the whole area. 

Boron and copper and cobalt and molybdenum present special difficulties as the applied amounts are so small. These are best dissolved, and applied with a sprayer. Borax is not very soluble, so instead you can use Solubor (which has 20% boron) at half the rate of borax (which has 9% or 10% boron) for large areas. Use warm water in your sprayer when dissolving borax and agitate frequently when spraying. With all dissolved minerals, but especially borax, check the bottom of the sprayer when done. If you see solids there, add more warm water and go over the area again. The amount of water in the sprayer is not important, just evenly cover the area with the proper weight of mineral. I have mixed copper sulfate and borax together in a sprayer and applied both at the same time; it works ok. Once I was unable to obtain cobalt sulfate, and applied cobalt carbonate with a sprayer, even though the cobalt carbonate wouldn’t dissolve. I removed the spray tip (the part with the tiny hole) and agitated the sprayer while applying the cobalt carbonate. 

Always look up the MSDS (Material Safety Data Sheet) before handling any of the minerals. They are certified OMRI Organic, but don’t use them without appropriate caution. Copper sulfate, cobalt sulfate, molybdenum sulfate, and to a lesser extent manganese sulfate deserve extra special handling.  This means keeping them off your skin and out of your mouth, nose, eyes and lungs.

Many experts recommend letting the minerals settle in 2-4 weeks (depending on temperature) before seeding or transplanting. I like quick rotations, so I have generally ignored this warning, with unknown but not disastrous consequences. Maybe I have gotten away with this because my favorite nitrogen source is slow release feathermeal. I found that when I planted or transplanted right after a soybean meal application I was wasting my time and seed and even transplant seedlings.  Failures prompted me to search the web and I found this study by Brown and Davis. If you are using soybean meal as a nitrogen source, you really need to let it rest 2-4 weeks.

I think of most of the minerals as building a background of fertility which we hope will feed the microorganisms, and then the plants. However, boron and sulfur are anions (so is nitrate nitrogen), they leach, and they usually need to be applied for every crop. Nitrate nitrogen is water soluble and leaches too. The amounts of boron and sulfur (which is usually applied as gypsum) are quite small, so there is no problem spreading them evenly over the planting area. Nitrogen is another matter. We use lots of it and it is expensive.

A question comes up around nitrogen fertilizer as to whether to fertilize the whole area pre-plant, to side-dress the plants pre-plant, to dig the N amendments into the soil under the transplant, or to side-dress a few times during the growing season. I have used all these techniques with success. In addition, I will often apply a liquid fish at critical junctures during the growing cycle. One should be careful to fertilize with additional liquid N only when the plants are growing. Excess N at the wrong time leads to weak, unhealthy plants – the perfect food for insects, not people.

Phosphorus is immobile. Mix well into the soil. Zinc is immobile. Mix well into the soil.

When amendments cannot be dug in…

OrganiCalc assumes the minerals will be mixed evenly to the depth of your soil sample. If you cannot mix the minerals into the soil, as in an orchard, you can safely apply amendments at half the rate of the 6 inch (15 cm) recommendation, fertilizing to a 3 inch (7.5 cm) depth. (However, at least one very experienced analyst recommends applying the whole 6 inch amount.) In subsequent years gypsum will help carry the minerals downward to a certain extent, so it is best to plan on applying part of any calcium requirement the second or third year, as gypsum. If you can, apply a mulch to cover the minerals, and let the roots grow into the mulch.

If you can’t mix the minerals in, stratification will be an issue, especially if water is limited. Subsequent soil tests should be at different depths, from 1 to 6 inches.

It will be important for you to understand how minerals move in the soil.