Over a year ago we talked about greensand as a soil amendment however it is much more than that since it is loaded with nutrients. 

Greensand has been used for over 100 years as a natural source of a slow release fertilizer and soil conditioner. The slow release of potash and phosphate does not burn plants and the minerals improve the moisture holding properties of soil. 

For years many gardening books and horticultural publications talked about the importance and value of New Jersey greensand. However shipping it into Houston was extremely expensive as it can weighs over 3,000 pounds per cubic yard. About 15 years ago several deposits of greensand were discovered in Texas and now it is only pennies per pound! It is the most economical way of adding a huge range of nutrients to your soil. 

 

Origin of Greensand 

Greensand was formed in anoxic (without oxygen) marine environments that are rich in organic detritus and low in sedimentary inputs. As in fish emulsion, seaweed and other products from the ocean it has all the nutrients (elements) found in seawater (see chart below). The geological formation is a sedimentary rock known as “Glauconite”. It is often an olive-green colored sandstone like rock found in layers in many sedimentary rock formations of marine origin. It is called a sand due to its crumbly and grainy nature, but in reality the minerals are very similar to clay minerals.    

Since greensand was formed under pressure in deep oceans and without oxygen the mineral complex’s become unstable after being mined and exposed to oxygen at atmospheric pressure, hence these nutrients are released into the soil. 

Greensand in our area is a dark greenish gray color when dry and turns almost black when wet when it is first mined. Greensand is a very heavy mineral with a density of approximately 90-120 pounds per cubic foot (2,500-3,000 pounds per cubic yard) depending on moisture content. 

The minerals are normally released slowly over time but occur much faster in organic rich soils full of beneficial microbes (microbes produce organic acids as they break down organic matter which facilitates the release of the minerals for plant absorption). The pH of greensand varies from slightly acidic to slightly alkaline depending on the source and has little effect on the pH of soils. Some greensands can contain up to 12% iron (Fe). As greensand weathers (starts to breakdown and oxidize) the iron combines with oxygen (O) and the color becomes rusty looking. 

Note: This oxidizing process of iron is what gives many of the iron rich soils in East Texas their reddish color. 

Most of the soils around Houston and along the Gulf Coast tend to be very nutrient deficient. We are located far from any areas where the weathering of igneous rocks would release the required minerals and allow them to be deposited in our soil for plants to use. Historically, we also receive a lot of rainfall. The slight acidity of rain tends to make these minerals soluble and allows them to be leached out of the soil. The result is our area soils tend to be very low in the minor and trace elements. This is why it is so important that we have lots of organic matter in our soils to feed the microorganisms. These guys will absorb the nutrients into their bodies and prevent them from leaching. As they eat each other the nutrients are released into the soil and the plant roots can get them. For example fungus will form calcium oxalate crystals on their hyphae and store it into the soil till it is needed. Blossom end rot on tomatoes is an example of a calcium deficiency and some weeds like Dandelions require soils low in available calcium. 

Traditionally, we were taught that plants can grow with only 16 elements. However recent research has shown that plants grown with a much wider assortment of nutrients have less disease and insect problems, use less water, taste better, have larger and more fragrant flowers, etc. The human body has 90 elements in it and if  they are not in the soil then plants cannot absorb them and we do not get them when we eat the plants and fruits, nuts, etc. and many health problems are the result. 

There is an excellent lecture available on CD on the importance of trace elements. It is called “Dead Doctors Don’t Lie”, By Joel Wallach, DVM, N.D, (available at many health food stores or online). It explains why we have so many health problems are associated with the lack of nutrients in our food supply. Almost all of Dr. Wallach’s statements have been confirmed by other researchers since this lecture was recorded many years ago. This is a fun lecture to listen to, as Dr, Wallach has quite a sense of humor as he explains the importance of trace elements for both animal and human health. 

In December I was able to attend a multi-day workshop on advanced soil science. During the seminars several of the speakers talked about the role of these micro and pico-nutrients working as co-factors in enzyme reactions for both plants and animals including humans. The research showed that a lack of these elements prevented the enzymes systems from working properly and led to more insect and disease problems in plants and health problems in animals and humans. 

Additionally I was given a copy of the newest edition of a book on diagnosing plant health and nutrition problems that goes well beyond the obsolete 16 nutrient model of plant health. 

Plant Analysis Handbook III – A Guide to Sampling, Preparation, Analysis, and Interpretation for Agronomic and Horticultural Crops, Multiple Authors, Micro-Macro Publishing, Inc., 2014, ISBN: 978-1-878148-01-8 . 

 

Uses of Greensand 

Greensand often has the consistency of sand but is able to absorb 10 times more moisture which makes it a good amendment for use in agriculture and horticulture for many soils types. Greensand does not burn plants and helps the beneficial microbes to grow in the soil. It also has been found to be a good conditioner to help loosen heavy and tight soils and help bind loose soils. 

Recommended application is 2-4 pounds of greensand per 100 square feet, 40 pounds per 1,000 square feet or 1 ton per acre. For potting soils 5-20 pounds per cubic yard can be beneficial. It is a good idea to repeat this every few years to replace the nutrients that have been used up or leached from the soil.    

Many gardeners add a few cups of greensand to their compost bins to increase the nutrient density. I like to sprinkle a little greensand in my worm bin (vermi-composting) to add some mineral roughage that helps the worms eat the feedstock and it increases the nutrient content of the castings. 

A field test by Rutgers University in a sandy loam soil with greensand applied in the row at the time of planting, found that the application of greensand increased the yield of potatoes by 16%. 

The benefits of greensand, largely unexplained by scientific research are far more than a laboratory analysis would indicate. However numerous greenhouse and field studies have shown significant improvement in the growth of plants. Other studies have shown that the use of greensand improves the taste, color, nutritional value, the health of plants and the health of soils. 

Note: The crushing process of the glauconite ore produces both greensand and rock. The rock can be screened to different sizes and used as a landscape rock. It gives a very different look than commonly used gravels, crushed granite or basalt. The green rock portion when used on pathways packs well, is black when wet and greenish grey when dry. The greenish grey color makes yellow flowered plants (Daylilies, Tunera, etc.) stand out and really “sizzle and pop”. 

 

SUMMARY: 

Greensand is the most cost effective method of adding minor, trace, micro and pico nutrients to ones soil. Always look for screened greensand where the rock portion has been removed. 

 

PROS: 

– good source of iron phosphorous, potassium and calcium 

– inexpensive 

– good availability 

– available in bag or bulk 

– nutrients moderately available 

– easy to use    

– often used in compost piles to enrich it 

– almost a unlimited resource 

– good for all plants 

 

CONS: 

– may be dusty when dry (wear a mask) 

– not a complete fertilizer 

– some lower cost brands do not screen it to remove rock portion 

 

BOOK REVIEW: I find one of the benefits of the winter and holiday season from Thanksgiving through January is that gardening slows down. As a result I get caught up on my reading from numerous books, research articles and other materials. Another book I read this winter was: 

“TOXIN TOXOUT Getting Harmful Chemicals out of our Bodies and Our World”, Bruce Lourie and Rick Smith, 2013, Knopf Publications, 

ISBN: 978-1-250-05133-2 

This is the second book by these two authors. Their first book “Slow Death by Rubber Duck- How The Toxic Chemistry of Everyday Life Affects Our Health” became an international best seller. 

This book reviews many of the toxic chemicals we come into contact with every day and the health problems they cause from allergies, autism, cancer, and many more. It also offers alternatives and ways to remove these toxic chemicals from our bodies. It strongly reinforces the concept that most experienced gardeners already knows: healthy soil = healthy food = healthy bodies. 

This book is an easy to read overview of what has happened, the consequences and how to remove toxic chemicals and recover from the damage that has been done to our bodies.