Greensand

Greensand is an organic fertilizer that contains the deposits of minerals that were once part of the ocean floor. It is mined from 70-80 million year old marine deposits consisting of iron-potash-silicates and marine trace minerals. Also called "glauconite," greensand has a bluish-green color. The green color is due to variable amounts of the mineral glauconite, a naturally-occurring iron-potassium silicate with the consistency of sand but 10 times the moisture absorption.

For slow-release potassium and trace minerals greensand supplies marine potash, silica, iron oxide, magnesia, lime, phosphoric acid and 22 trace minerals. The NPK ratio is approximately 0-0-3. It has a naturally high cation exchange capacity, resulting in a slow release of potassium, useful for building the soil's potassium reserves, but not appropriate for quick remedy of a potassium deficiency.

How does greensand work? For most part it is unexplainable. However, numerous trials show its efficacy. One possible explanation is mineralization, which improves soil life by increasing populations of certain bacteria that slowly dissolve insoluble mineral nutrients.

You are smart can we be friends?

Me too, me too....I wanna be your buddy too GB

I forgot that I wanted to talk about how long it takes greensand to breakdown. Because it is not water soluble, the nutrients only become available after microorganisms in your soil digest it. I have read that greensand can take as long as 7 years to fully breakdown.

GB, if it takes that long to break down, how useful would it be for short-term indoor grows ? Can I assume that enough is digested by the micro-herd to be useful ?

As with bone meal, I think greensand is most useful to container gardeners who make a batch of potting mix and allow it to sit for a few weeks before use.

However, if the microbial life in the potting mix is healthy and diverse, they will begin to churn out useful levels of goodies from the greensand within a week or 2 of application. I have seen visible 'green up' occur within that time span. Greensand is also an amazing soil conditioner. It improves drainage while simultaneously improving moisture retention, and provides nutrition for both the plant and the microbial life.

Greensand comes from TX and NJ. The TX product has NPKs of about 0-2-5, and contains about 20% Fe, and 2% Mg.

mwmba has provided some great info here. I would add that container gardeners who recycle their soil benefit several times over from a single application. Recyclers should keep track of greensand usage, IMO. As it tends to hold moisture, one should be sure not to get too much sand in the mix. Being that it takes so long to breakdown, over usage in recycled soil can also lead to nutrient and micronutrient imbalances. Leaning on the side of less is more, I would add to my soil mix once. Then, as I recharged old soil, I would only add greensand to new soil being added to the mix.

Bringing Mulder's chart to mind...