Dinosaur Period Expanded Shale – for Gardens
By George Giltner, Adv. Master Gardener, MS Biology
A garden soil recipe for success is to add a soil conditioner that originated from the Late Cretaceous Period, when the most famous mass extinction of dinosaurs occurred, 65 million years ago. In this time period, Tyrannosaurus and Giganotosaurus roamed, and flowering plants began to flourish. Fine grained sedimentary rocks from mud of clay and silt were laid down to form the Texas Midway Shale formation which is 10 -15 ft. underground in a pattern from Corsicana to Texarkana south to Laredo.
When shale from the above area is mined and exposed to 2000 deg C for 40 minutes, 65% of the silica makeup changes chemically as gases escape to form a porous lightweight rock, Expanded Shale. It can absorb 38% of its weight in water for a water-wise soil amendment. Also it will conservatively last for decades, unlike deteriorating vermiculite and decomposing peat moss. Expanded shale is mostly an alumino-silicate that will not change the soil pH, is non-toxic and inert, and environmentally friendly. It enhances plant growth and performance. Applications include raised beds, window boxes, gardens, large container boxes, and in landscaping.
The porous structure of expanded shale absorbs water, therefore any fertilizer components dissolved in the water will also be absorbed onto the aggregate, porous-rock surfaces. Extension researchers from Texas and Florida, J. Sloan, P. Ampim, R. Cabrera, W. Mackay, and S. George (Moisture and Nutrient Storage Capacity of Calcined Expanded Shale), have tested the bioavailability of nutrients loaded onto expanded shale by using Romaine lettuce. Results demonstrated significant increases in the size and the mass of yield. Shoot mass increased linearly from 0.1 grams with no fertilizer on expanded shale to 1.9 grams/pot with 100% fertilizer-treated expanded shale. No additional fertilizer was needed for the 45 day crop rotation.
Dr. Steve George, Texas Agrilife Extension Service horticultural researcher in Dallas, recommends this expanded shale to “open up and aerate clay soils faster than any other product tested”. His shale research work is extensive with two years of study and 6 years of field trials. Expanded shale increased soil porosity (for drainage and aeration), reduced compaction (for healthier root systems), and insulated roots from temperature extremes.
Jim L. Turner, director of horticulture research at the Dallas Arboretum, praises its use for solving watering issues as overwatering causes more plant deaths than any other cause. Expanded Shale is used extensively throughout the many beautiful gardens in the Dallas Arboretum to optimize water usage and conservation.
In your own gardens, utilize expanded shale by adding 3 inches of compost and 3 inches of expanded shale, then till to 8 inches deep. Add top mulch to the mixed soil with a layer 3 inches deep. Continue mulch additions spring and fall. Soil tests may reveal that additional commercial fertilizer is not needed due to decomposition additions from nutrient balanced mulch.
For containers, fill the bottom quarter with expanded shale, then add a mixture of 1/3 of each – expanded shale, compost, and garden soil. Also add mulch to the top of the container. Due to our very hot summers and intense tropical solar light, use wood or other insulating material to reduce the temperatures on the surface of the container when the heat comes. Always use a water meter to confirm moisture levels of your container soil. Rain water is recommended due high sodium values (>100 ppm) in some of our local tap water supplies.
By late Spring 2014, an application-test demo plot will trial expanded shale and zeolite amendments to grow various garden vegetables in the Beauregard Demonstration Garden in DeRidder, La. The initial soil was basic kaolinite clay subsoil with little nutrient value and low ability to retain nutrients. In early November, compost and varying additions of zeolite were added to specific rows. LSU AgCenter soil tests have indicated high nutrient values 6 weeks later in mid-December. Identical mass of expanded shale will be added to ½ of each row. Then in mid-March various vegetables will be planted. Practical observations like yield, water meter readings, soil nutrient tests, soil bulk density, and plant health will be observed. This Master Gardener application test is not meant to be a scientific experiment as the scope, time, and expense would be beyond volunteer resources.
Dinosaur dirt (Texas expanded shale) and porous volcanic rock (zeolite) soil conditioners have demonstrated their value in nutrient and water conservation by numerous scientific tests from NASA to University Extension Service experiments. The nutrient cost-savings and environmental benefits of these products can be employed in cropping, forests, and in small-space gardening. Experiments have proven that soil beneficial microbes are enhanced with greater moisture control, nutrient retention, and soil porosity, which should increase yields and Ag success. “Let’s give it a try!”