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AXIS UC Davis Plant Available Water

Mon, 18 May 2020 04:00:00 GMT

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Long Term Follow Up

Mon, 18 May 2020 04:00:00 GMT

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Adapting in the Desert

Mon, 18 May 2020 04:00:00 GMT

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Nevada DOT responds to water and budget limitations for landscapes.
Embracing soil as an important player in water conservation, the ASLA Water Conservation Professional Practice Network spotlights the Nevada Department of Transportation (NDOT) Landscape Architecture, where they have adopted a standard policy of “no irrigation” for southern Nevada freeway landscape enhancements. To respond to that challenge, designers are utilizing porous inorganic amendments as an aid to increase plant-available water in the soil in a region where rainwater harvesting challenges are unique.

While many of us think of amendments as organic, Internally Porous Inorganic Amendments, or “porous amendments”, are non-biodegradable minerals that provide physical and structural improvements to soil – above what solid soil granules and organics alone can provide. The most widely used porous amendments are Calcined Diatomaceous Earth, Calcined Clay, and Zeolites, which are all currently approved by the United States Golf Association for golf green rootzone construction. They have the ability to increase watering efficiency by improving infiltration, increasing water holding and plant available water; and exchange air and water continuously with an abundance of internal pores that are the proper size to absorb and release water readily.

Lucy Joyce, head of the Landscape Architecture Section for NDOT sums up the dilemma. “In the Las Vegas area, we receive 5” or less of rainfall per year. Water is a scarce and expensive resource. NDOT has been utilizing sustainable practices and promoting water conservation through the use of native landscaping and techniques which do not require supplemental irrigation. Moving to a “no irrigation” policy reduced the maintenance for our staff while also eliminating the costs for water meters and ongoing water bills. Adding porous amendments helps bridge the gap from planting to establishment for us and our contractors.”

For some initial projects, Cary Baird, Senior Associate and landscape architect with Stantec Consulting Services, Inc. has recently designed and supervised several projects for NDOT and Clark County – all within urban Las Vegas.

“Our design goal was to bring the undisturbed native desert into the urban fabric of a city while reducing long-term maintenance costs. Our plant palette consists of local area native plants and other plant species we introduced from the Mojave Desert that grow in similar climate conditions as Las Vegas. Our design process evaluates the site soil, the plant’s natural air, water and temperature requirements, as well as potential microclimate conditions such as paved area heat gain. Then we generate a custom planting design and backfill blend.”

“All projects that use these unique water harvesting techniques require temporary irrigation from water trucks to help with the establishment of plant materials for the first year. At the end of the establishment period, plants have been weaned to be able to support themselves with the natural rainfall conditions. AXIS calcined diatomaceous earth was applied at 15% by volume with various combinations of topsoil as soil agronomy tests helped determine. Typically, this was blended offsite and then placed as a backfill mix around each plant. AXIS has played an important role in improving the localized area around each plant by helping to capture limited rainfall and disperse water to the roots over a longer period of time. So far, we have been pleased with the plant survival rate with this new approach, and the product has been instrumental in that success.”

Visit the NDOT Landscape and Aesthetics program’s website for more information, click on “Projects and Programs,” and select “Landscape and Aesthetics.”

by Matt Mathes, ASLA, co-chair of the Water Conservation PPN

Learning from an Island

Mon, 18 May 2020 04:00:00 GMT

"Salvaged topsoil is amended with diatomaceous earth to increase water retention and eliminate the need for a permanent irrigation system."

F or a "school in the woods," Island-Wood is not very deep in the wilds. But a stay at the 255-acre learning center on Bainbridge Island—just a ferry ride from Seattle—is not to be confused with camping. It's more of a lesson in how environmental education and sustainable design work together, and how far the limits can be pushed when resources, commitment, and imagination are available.

Respect for the land is designed into Island-Wood. From the moment they debark for their three-to-four-day stay.

School kids play on the suspension bridge that spans a deep ravine and several microclimates at Island-Wood. The center for environmental education, right . is designed to preserve) existing ecosystems and recycle water through landscape features such as constructed wetlands on site.

Learning from an Island
(Oct. 2003 ASLA Magazine)

Near Seattle, kids experience an ace-friendly campus.

BY CLAIR ENLOW

Visiting school kids can see clearly where their feet should go. Earth-colored paths—made of pounded, recycled concrete rubble—thread around giant firs as they lead away from the world of cars and houses and in-to the site. The forest floor, with its layers of duff, sticks, and snags, is right there at the tough edges of the walk. Visitors will find pushcarts just past the sheltering portal to help them cake their essentials out along a network of pads to their assigned housing. Each bunk has a small window on the woods.

The built campus is a loosely affiliated gathering of institutional-sized structures dominated by unconventional colonnades of recycled logs paired with industrial details and materials. Solar panels cover one side of the butterfly-sloped roofs, which are also designed for passive solar gain. But the buildings only cover about 6 percent of the site. The rest is a restored natural landscape and a living laboratory.

At the center of campus, students visit a laboratory for leading-edge environmental technology, above. The "Living Machine" cleans gray and black water for reuse in toilets on the site. Rain-harvesting cisterns, below, store water for the organic garden.

Restoring landscapes and preserving ecosystems—even as major construction is taking place—is a call landscape architect Tom Berger, ASIA, has answered for 25 years. It was that long ago that his firm, the Berger Partnership, began daylighting and restoring creeks in Seattle neighborhood park projects. At IslandWood, Berger was able to translate a long-held passion for restoration and regeneration of natural systems into a teaching and learning environment.

'The idea was to make the least impact on the land—and yet make the most profound statement about the land,' says Berger. His firm had worked with the architectural firm Mithunon the REI corporate headquarters building in Seattle, which brought a little of the forest hack into the city and won widespread recognition for sustainable design (see "Street Corner Wilderness," Landscape Architecture . July 1999). Both the Berger Partnership and Mithun were handpicked by IslandWood founder Debbi Brainerd to demon-saute sustainability at the learning center. They worked as a team from the scan of the project in the fall of 1997 until completion in the summer 42002, with Berger primarily responsible for site planning and restoration.

Campus buildings are restricted to less than 6 percent of IslandWood, which encompasses a nearly complete watershed. The four-acre pond, cattail marsh, and stream connect to a saltwater estuary park just outside the bounds. Streams and wildlife are constantly monitored by students and staff, and invasive plants are gradually being replaced by native species.

Biomass basics, IslandWood style

Nearly 100 percent of the biomass of the site was retained at IslandWood throughout the restoration project. This achievement, which helped the project to win the coveted gold LEED (Leadership in Energy and Environmental Design) rating from the U.S. Green Building Council, was made possible by several measures built Into the construction process:

Harvested wood, snags, and forest floor duff were stockpiled during construction. New planted areas are mulched with chipped green waste material.
Site restoration included the location and eradication of invasive plant species and re-vegetation with native plants. many of which were salvaged during construction.
Rock piles and brush piles made of site-salvaged logs and branches encourage the presence of wildlife.
Salvaged topsoil is amended with diatomaceous earth to increase water retention and eliminate the need for a permanent irrigation system.

Propagated and reintroduced native plants were able to take advantage of the rhizomes and microorganisms naturally present in the retained forest floor duff to quickly reestablish themselves.

A Sustainable Worldview

Now in its second summer of operation, IslandWood provides a window on a whole ecosystem at work—providing food and clean water for humans as well as everything necessary for many species of wildlife. By design, it also gives visitors experience with the future of environmental science and technologies, with professional staff to show the way.

The typical IslandWood student is 11 years old and carries a small pack with special equipment like a pH testing kit, a measuring tape, a float for calculating stream velocity, forms, pencils, a sketch pad, and maybe a calculator. Gathered data will be entered into a system set up to monitor water quality in the small creeks on site, and it may be used to generate a presentation on environmental science back at school in the city. Some classes go on to test more streams in their own neighborhoods.

The kids listen to local storytellers and make up some stories of their own, draw sketches of wildlife, play charades, and read their poetry around the campfire. They take their food wraps out to the compost bin, where they learn vermiculture in the organic garden.

While much of the curriculum is in the woods, education also takes place in the laboratory, in the kitchen, and in the studio. The campus includes a central lodge with reception and assembly areas, a dining hall, educational studios, a creative arts studio, and sleeping lodges. Special field structures, including a suspension bridge, forest canopy tower, floating classroom,bird blind, mill worker's cabin, and tree houses, enrich the learning environment.

"The center is a magical place where children and visitors can develop greater understanding of the Puget Sound native ecology—and reduce their own ecological foot-print," says Berger.

Design team members from Mithun and the Berger Partnership camped on site with the client at the outset of the project, hacking through invasive blackberry brambles on the former tree farm and making a map of opportunity and imagination.

The dream was to link constructed and natural systems in new and interdependent ways, building in the means of regeneration and renewal. And the reality is now a hardworking environmental laboratory. At the center of the campus is the glass-enclosed "Living Machine," a wastewater treatment facility char treats blackwater using natural processes. Pipes and wetland cells are exposed to view so that children can experience and intuitively grasp the workings of the system. Water used for a flush toilet and for watering of nonfood plants is returned to the system for cleaning and leaves the greenhouse visibly clear.

At lodge entrances, the design team used logs salvaged from the former tree farm's holdings and boulders salvaged from construction. A crushed, recycled concrete aggregate base course Is used for paths and paving.

The organic garden with raised beds, a green-house, a composting bin, a water-harvesting system, and demonstration areas provides an outdoor classroom and laboratory for cultivating food plants. Food grown in the garden is harvested by students and staff and used in meals prepared at the center, and scraps are composted and brought back to the planting beds. The garden nursery is used to propagate native plants and reestablish them in the areas where invasive species were removed.

Natural landscape and lodges are intimately connected at IslandWood, where clearing of trees was restricted to 15 feet outside building perimeters. Much of the second-growth forest has been carefully restored to natural conditions. Recovered forest duff is scattered over mulched areas near new plantings.

Designing for Nature

Building a campus for hundreds of out-of-town students was not an easy sell for Bainbridge Island, where many have chosen to live for its rural setting. Although the tree farm years had degraded the forest environment with chainsaws, tractors, and crash, the neighbors had enjoyed freedom of access to the IslandWood site. Generations of local kids had grown up exploring the forest and swimming in "Mac's Pond" there.

Opposition to the project was finally put to rest through assurances about noise and traffic disruption, as well as the knowledge that the site was sure to be developed anyway. Island Wood would be an environmental asset, a resource for local schools, and a good neighbor. The same group chat originally voiced objections finally helped in the exhaustive process of identifying, inventorying, and weeding out invasive and nonnative species on the site.

The boundaries of the property en-close a nearly complete watershed with a wildlife habitat, salmon spawning streams, and a rich diversity of ecosystems, which include a four-acre pond, cattail marsh, bog, scream, and dramatic ravine. There's access to an adjacent salt-water estuary park.

With IslandWood—as with many sites—finding the place where the man-made landscape ends and nature begins is a difficult proposition. The land, a thrice-logged tree farm and second-growth for-est, had an artificial lake that was built more than 100 years ago to supply water to the sawmill and was later stocked with invasive species. Such existing conditions challenged the design team to make trade-offs between four occasionally competing priorities, according to architect Burt Gregory of Mithun. Those priorities were "education, experience, economics, and environment." The design team decided to keep the pond and the wetland habitat that goes with it.

Low environmental impact was such a high design priority, it would be safe to say the loggers who previously occupied the land had a substantial role in the plan of the site. All of the campus buildings were positioned on level areas that had been previously cleared. Because of the desire to limit construction impacts and vehicular access, clusters of buildings were placed at or near property perimeters. Once the general outlines of the logged areas were established, an exhaustive inventory of trees was conducted, and the dimensions and orientations of the buildings were adjusted. After the site was cleared of invasives and underbrush, the buildings were staked. In general, structures were placed on a north—south axis at the northern edge of "solar meadows" in order to maximize passive solar gain.

One of the most dramatic natural features of the site is a steep ravine. It would have been tempting to lead kids down the slope so they could experience the changes in microclimate and the closeness of a fast creek, but the design team agreed that this would be coo great a threat to the health of the scream. Instead, they lobbied for a long suspension bridge over the ravine, one where kids could cake in a whole section of the landscape. The graceful metal structure is now one of the most popular places on site.

New trails, boardwalks, and bridges are threaded through the site to avoid sensitive habitat and natural systems. Primary pedestrian circulation follows a historic logging road, and trails are constructed using native soils. 14 important to make the transition from a standard country road to one that has been located so that you really do feel you are in a sanctuary," says Berger.

Bringing utilities into the site was a special challenge, since trenching and pipes can result in tree die-off due to dewatering. The problem was resolved by running utilities directly under the main paths through the site. Walking surfaces were raised off the forest floor so that lines could be buried with little disturbance to the existing root systems. The resulting paths, with gentle embankments, are at once connected and lifted from the forest floor. Construction access was strictly con-fined to circulation mutes, and crews literally swept them off as they withdrew from the site.

Students, visitors, and guests see recycled materials in new applications that enhance the beauty, usefulness, safety, and accessibility of the site and its buildings. Crushed recycled concrete is used for parking and walking surfaces to minimize runoff from pavement, and trail paving is made of a crushed recycled concrete aggregate base.

Bike racks were constructed on site using site-salvaged cedar logs. A walk-way connecting the main lodge and dining hall is built with plastic lumber, a natural-looking recycled material. A site-salvaged rock "rumble strip" at the dining hall warns sight-impaired visitors using canes that windows swing out from the side of the building. Patio pavers at the guest cottage are made of crushed re-cycled glass. At the parking lot, impact curb wheel stops are composed of mixed post-consumer and postindustrial plastics and auto-shredder residue.

As man-made landscapes like the organic garden mature within the larger natural setting, the impacts and responsibilities of humans can be better understood, according to artist Lorna Jordan, whose ideas served as a catalyst for the design concept in the beginning stages. "People who under-stand their own habitats are more likely to become stewards for those of other species," she says. - LA

As man-made landscapes like the organic garden mature, the impacts and responsibilities can be better understood.... "People who understand their own habitats are more likely to become stewards for those of other species"

Scores of Pores

Mon, 18 May 2020 04:00:00 GMT

No matter if you’re growing in containers, hydro, or outdoors in soil, diatomaceous earth is an incredibly versatile material that helps with prodigious root systems, silica uptake, and pest control.

DIATOMACEOUS EARTH

One of the coolest things about diatomaceous earth (DE) is that it was originally plankton, meaning it went from being an organic material to a mineral. But how could that be? And what exactly is DE?

Well, in the time of dinosaurs, give or take an epoch, plankton flourished in lakes and seas. These plankton species multiplied to countless proportions, especially during volcanic periods, when they consumed carbon dioxide (CO2) and extracted silica from the water. The silica was ingested to support cell walls that grew into beautiful, microscopic, porous silica structures. These plankton bodies were so porous that water flowed through them, providing a continuous supply of nutrient absorption. When they died, they sank to the bottom and accumulated in vast numbers as sediment. The skeletal remains of these structures are called diatoms. Eventually the waters receded, the topography changed, and these huge deposits of diatoms were discovered and named “diatomaceous earth.”

Today, DE is mined much like sand or gravel. (For the record, DE contains amorphous silica, which is the safe kind.) Of course, DE is not one universal product. In the green industry, natural DE powder is used for insect control, while DE aggregates improve soil function for all types of plant applications. Natural DE powders are different from powders used for filtration purposes, which are combined with other ingredients and kiln-fired to create better properties for separating particulates.

In the green industry,

natural DE powder is used for insect control, while DE aggregates improve soil function for all types of plant applications.

Natural DE powders have no additives and, as mentioned, are designed for use on insects and plants. Under a microscope, powdered DE is made of a whole lot of broken diatoms. To an insect, these are extremely sharp, hard edges that resemble a minefield of broken glass, cutting and abrading away their waxy layered exoskeleton. Insects get severely injured in their joints and bodies. They desiccate and they die. They can’t build up immunity because it is a mechanical mode of action.

Diatomaceous earth powder is blended into potting mixes to control insects at two to three per cent by volume. It can also be applied topically on the ground, applied to foliage as a dust with a puff bottle or hand-cranked blower, or mixed as a wettable powder to spray onto the top and underside of leaves. It is safe to use on food up to 24 hours before harvest, but just be sure to always wash your edibles before eating them. Even food-grade DE powder,which can be used in food production, such as mixing it with grains during storage to keep bugs away, shouldn’t really be eaten (though we hear people use tiny amounts as a supplement and testify to results).

Diatomaceous earth in aggregate form is very versatile, comes with some compelling research, and is challenging traditional soil component choices in the greenhouse, nursery, potting soil, and hydroponic markets. Aggregates enjoy wide acceptance for rooftop gardens, outdoor gardens, structural soil, sports fields, landscapes, and bioswales. They can also be used in lieu of or in combination with peat moss, and mixed with sand for golf green construction.

Diatomaceous earth aggregates have unparalleled physical properties designed by nature. They are 82 per cent porous and very absorbent (up to 142 per cent their weight in water), giving them great potential to influence water conservation. To help retain nutrients, they also have a cation exchange capacity of 27. Absorbed water and waterborne nutrients are readily released and available to plants.

Aggregates show impressive measurable increases for improved infiltration rates, water-holding capacity, plantavailable water, and increased air and water exchange. They also increase porosity, serving as additional reservoirs of pore space where air and water can exchange into, and out of, the granules, unit for unit, as moisture fluctuates. This creates a much more interactive soil media for root growth, water uptake, and nutrient uptake.

Aggregates show impressive

measurable increases for improved infiltration rates, water-holding capacity, plant-available water, and increased air and water exchange.

Aggregates promote easier establishment, excellent plant health, and legendary root mass due to increased air capacity and circulation, coupled with consistent reports of silica uptake. They are also pH neutral, and because it is a mineral source of pH, it tends to stabilize pH in soil and hydroponics. They reduce compaction, are essentially permanent, and perform long-term.

Remember how water flowed through the living plankton structures? The pores in DE aggregates have been identified by studies at the University of Augsburg as the same pore size that determines plant-available water (plants have an easier time getting water from pore spaces than from water as film on soil particles). Perhaps you’ve heard that if you want to reduce irrigation, just improve plant-available water. Well, DE aggregates have more plant-available water than peat moss, four times more than compost in native soil, and 90 per cent more than calcined clay from water release curves. This is worth considering if you want soil moisture uniformity and controlled wetting and drying, and if you believe in conserving water.

Diatomaceous earth

in aggregate form is very versatile, comes with some compelling research, and is challenging traditional soil component choices increased air and water exchange.

When it comes to soil water pores, there are three types: larger, free-draining pores; appropriately sized, plant-available water pores; and smaller, less-available water pores. Diatomaceous earth pores are invisible to the naked eye, so visible pores in other media indicate free-draining pores with less water retention and less plant-available water.

When we scan other inorganic choices for soil mixes and hydroponics, we see perlite, pumice, and clay spheres. (Though formerly organic, DE aggregates are inorganic amendments due to the silica transformation into a porous shape and from the kiln firing that reduces any organic fraction.) These other choices are all assumed to be porous, but the active porosity is skin deep. Only the surface pores can interact and contribute to physical activity within a mix, as the internal pores are isolated air bubbles trapped within mineral bodies. This represents a considerable amount of soil mix volume that is limited from interacting with air, water, roots, and other soil components.

Another advantage of DE aggregates is that they do not float. Aggregates come in a variety of sizes: larger grades (3/8 to ½ inch), which are suitable as inorganic hydroponic mediums; coarse and medium grades (3/8 to 1/8 inch) for soil mixes and potting mixes; and a fine grade (like large sand) for use with potting soils to improve soil performance, with the added potential for insect control. Some veteran growers. may remember large DE chunks for hydroponics. Well, that super-size aggregate is available again and it rivals the best current mixes and inorganics. You can mix it at either 100 per cent by volume, or at 40-60 per cent and mixed with an organic. Users at these rates also remark they have less bugs.

The pores

in DE aggregates have been identified by studies at the University of Augsburg as the same pore size that determines plantavailable wate.”

Incorporating medium size DE aggregates into native soils or soil mixes outdoors is a great way to ensure successful establishment of every plant. They provide permanent porosity to hard or sticky clay when mixed in at 10-15 per cent by volume. It provides excellent drought relief in hot climates and is suitable for turfgrass, trees, shrubs, gardens, and flowers. Moreover, each plant will enjoy an environment that is physically conducive to proper availability of water, nutrients, and pore space to grow.

For indoor containers, DE aggregates can be applied at 15-20 per cent by volume. Again, this will increase the water-holding capacity, homogenize moisture content throughout the pots, provide more plant-available water, and reduce watering needs. (Of coures, outdoor containers with DE in the mix will experience similar results, but there will be a higher contrast between moisture levels becasue of increased evapo-transpiration.)

Yes, DE is kinda cool. The porous structures are reminders of how they formed, how they work, and their modes of action. Best of all, they offer ideal solutions for plants and soils.

A Natural Way to Kill Bugs and Boost Your Soil

Mon, 18 May 2020 04:00:00 GMT

Dig this: Fossilized remains of long-dead critters can lend new life to your cannabis plants.

We’re talking about diatomaceous earth (DE), the fossilized remains of phytoplankton or diatom algae. When they were alive, these freshwater organisms extracted nourishment from the water as it passed through their porous, silica-based exteriors. As they died, they sank to the sea floor and gradually created deposits.

So what’s the dirt on this versatile substance and its applications in your grow room? For one thing, DE works as a natural insecticide, but that’s only half of the story. As an aggregate, DE also goes to work in the soil, boosting its water holding capacity and infiltration.

Natural insecticide

When used as an insecticide, these fossilized remains are bad news for bugs. DE is an abrasive that gradually scrapes away an

insect’s exoskeleton, leaving it to dry out and die.

Using DE has several advantages over chemical insecticides. DE is an all-natural substance that’s safe to use and doesn’t harm the

plant. Furthermore, insects can’t develop a resistance to DE’s effects, said George Serrill, vice president of the Boring, Ore.-based

company EnviroTech Soil Solutions.

“With some chemicals, you need special equipment to handle it,” he added; DE, on the other hand, requires wearing only a particle

mask.

As an insecticide, you can apply DE in a variety of ways, including:

Mixed into the soil
Topically applied on top of potting soil
Mixed with water
Applied as a wettable powder. In this form, the DE comes as a powder, which you mix with water and spray onto the plant

If you use the powder, be sure to spray both the top and underside of the leaves. “The surface is easy to get,” Serrill said. “The

underside is harder to get, and that’s where a lot of insects reside.”

When applied in wettable powder form, DE will remain on the leaves for several days in dry conditions. However, the insecticide

washes off with water. So, keep an eye on your plants and assess whether to reapply after rain or heavy irrigation.

DE also comes in duster form. If you choose this application, consider moistening the plants first before dusting. Also be sure to

wear a particle mask when handling the dust.

Down to the roots

DE is an agriculturalist’s multitasker. In addition to its insecticidal properties, DE can also improve the exchange of air and water

under the soil’s surface.

Serrill said, “We also have aggregates that are working great to improve both water holding capacity and increase infiltration at the

same time, which are often thought to be mutually exclusive.”

Here’s how these aggregates work: Imagine a pot full of fine-grain sand. When you water the pot, the sand holds onto the water

longer. That’s because its infiltration—or the rate at which water moves through it—is low. Now, imagine a pot full of coarse-grain

sand. When you add water, the larger granules help the water drain quicker, creating an accelerated infiltration.

Finally, imagine soil enriched with DE in its aggregate form. The particles in DE are porous, enabling them to both retain water and

aid infiltration. “Diatomaceous earth in aggregate form can increase [water retention and infiltration] because it has internal

porosity,” Serrill said.

Soil enhanced with DE aggregates is able to exchange air and water more readily. And that’s important because air develops root

systems, which lead to better nutrient and water uptake, he said.

“For plants to grow, they also have to have proper moisture content and adequate air supply,” he said. “The DE in aggregate form

increases both.”

By Bridget Manley

Photo courtesy EnviroTech Soil Solutions

Nature’s Reservoir

Mon, 18 May 2020 04:00:00 GMT

by George Serrell

Having success in an indoor gardening department relies on many components. Here we tackle diatomaceous earth.

Any visit to a local garden center comes with a good dose of anticipation that you will find something new, pretty or useful. Ideas are inspirational and you can find lots of them.

Indoor gardening has captured our imagination because growers gain control of the atmospheric conditions of temperature and light. These controlled environments enable precise dosing of inputs through fertigation coupled with timed light exposure for specifically designed plant responses.

Hydroponic systems add an alluring dimension of speed to the process with faster cultivation from seed to harvest.

When selecting growing media components, one of the most compelling choices is diatomaceous earth (DE) because it has a fascinating organic heritage, a wide array of benefits and uses, and is available in powder and aggregate form.

DE Defined

Wait! What? OK, so what IS diatomaceous earth? Diatom is the root word in diatomaceous earth.

Diatoms are the skeletal remains of single cell algae. When these were living, water flowed through their porous structures so they could extract nutrients for growth. Diatoms reproduced by the bazillions.

These microscopic pieces died and accumulated as sedimentary layers on the bottom of lakes and oceans from long ago. Deposits of diatoms are called diatomaceous earth. They vary in quality, and deposits are chosen for their suitability for a particular use or purpose. It is mined and processed for a myriad of uses from liquid filtration, to industrial absorbents, to soil amendments.

DE comes from an organic plankton source, and products selected for feed additive, insect control, grain storage, pet and livestock dusting; and for plants, crops, soil, and soil-less media are eligible for organic approval by certification programs such as NOP and OMRI.

When selecting growing media components, one of the most compelling choices is diatomaceous earth.

DE is very lightweight and available in two forms, aggregates for indoor gardening, hydroponic media, potting soil, and multiple landscape applications; and all-natural powders as an all-natural mechanical insecticide that insects cannot become immune to.

Powder

DE powder for insect control is applied at 2 to 3 percent by volume, as a mechanical insecticide abrading and absorbing the waxy exterior protective layer of insects causing them to dehydrate and perish.

DE has a huge amount of surface area, which, to an insect, in or on the soil, translates to a deadly labyrinth of abrasive edges. Powders can be applied topically on the ground as a barrier to soil insects, blended into potting soil for prevention and larvae control, applied to foliage as a dust with a puff bottle or hand-cranked blower, or mixed as a wettable powder to spray onto the top and underside of leaves. DE powder is approved for use on cannabis by the state of Colorado.

Look for labels that claim control of specific insects. Food grade DE or labels approved for garden use can be used up to 24 hours prior to harvest; just be sure to wash your edibles well.

Aggregates

DE aggregates are very lightweight, reduce compaction and are kiln fired for stability. They do not break down and continue to perform long-term.

Aggregates come in a variety of sizes: larger aggregates (3/8-inch to ½-inch) suitable as inorganic hydroponic medium, coarse and medium grades (3/8-inch to 1/8-inch) for soil mixes and potting mixes, and a fine grade (like large sand) for use with potting soils to improve soil performance, with the added potential for insect control.

Aggregates also enjoy wide acceptance for rooftop gardens, structural soil, sports fields, landscapes and bioswales. Aggregates are applied at 10 to 20 percent by volume and show impressive measurable increases for improved infiltration rates, water holding capacity, plant available water, increased porosity and increased air and water exchange.

DE aggregates are 82 percent porous, with a cation exchange capacity of 27, to help retain nutrients, while absorbing more than their own weight in water. This water, along with water borne nutrients, is readily available to plants. Mixed into soils, DE aggregates serve as additional reservoirs of porosity where water is absorbed and released, constantly exchanging air and water into and out of the granules, unit for unit, as moisture fluctuates. This creates a much more interactive soil profile for root growth, water uptake and nutrient uptake.

If you think you will save water you will because the formula to reduce irrigation is equal to improve plant available water in the soil. In fact, studies show that DE aggregates contribute more plant available water than compost (UC Davis) or peat moss (Ohio State). Translation? You can reduce irrigation amounts or frequency. Your choice.

Indoor Potting Soils .

For indoor potting soils DE aggregates can be applied at 15 to 20 percent by volume. This will increase the water holding capacity, homogenize moisture content throughout the pots, provide more plant available water and reduce watering needs. You will also notice the material doesn’t float and water goes into the soil much more readily.

The signature effect is much more abundant root mass that ensures proper uptake of water and nutrients. It is also widely accepted that additional silica uptake is happening, providing more plant turgor and vigor.

Outdoor containers with DE in the mix will experience similar results, but with higher contrast between moisture levels because of increased evapo-transpiration.

Hydroponics .

For hydroponics, the largest granular size is used and rivals the best current mixes and minerals. A national brand research department leader said he “had never seen roots come out of the pot like that before.” DE is pH neutral, and helps keep pH levels consistent because it is a mineral source of pH. It should be rinsed well before use with water.

The same principals of porosity, absorption of water and nutrients, root production and silica uptake apply to this size aggregate. Materials like clay spheres and perlite do not have internal reservoirs to exchange moisture and nutrients, while other media with visible pores indicate pores that are too large and free draining, with less retention.

All the pores in DE, which are invisible to the naked eye, are the same pore size that determines plant available water (University of Augsburg, Germany). We recommend either 100 percent by volume, or 40 to 60 percent mixed with coco coir. Users at these rates also remark they have less bugs.

Landscape Soils .

Incorporating DE aggregates into existing or imported landscape soils is a great way to ensure successful establishment of every plant rung up at the counter. It provides permanent porosity to hard or sticky clay mixed in at 10 to 15 percent by volume. It is excellent for drought relief in hot climates, and suitable for turfgrass, trees, shrubs, gardens, and flowers.

Moreover, each plant will enjoy an environment that is physically conducive to proper availability of water, nutrients and pore space to grow. Specialty applications like rooftops rely on DE aggregates for meeting weight restrictions due to its lightweight properties. DE is uniquely suited for bioswale treatments, adding porosity to prolong the lifespan of areas designed to collect silt, fine debris and contaminants; while in roadside applications DE has increased survival of non-irrigated plants from 20 to 25 percent to 70 to 99 percent.

As you can see, DE aggregates and powders are arguably the most versatile material available for plants and soil because their utility and effectiveness spans multiple uses and cultivation methods including hydroponics, indoor and outdoor growing.

Give your customers’ soil the life-giving gift of additional air and water reservoirs with DE aggregates, and protect your plants from pests with natural DE powder.

George Serrill is vice president of EnviroTech Soil Solutions Inc. He can be reached at gserrill@ axisplayball.com.

envirotech

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(Oct. 2003 ASLA Magazine)