THE MANUFACTURED SOIL ENVIRONMENT-1/22/2020
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Presented at Invigorate U in January of 2020. Look into the process of interpreting, designing and testing engineered soils.
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THE MANUFACTURED SOIL ENVIRONMENT-1/22/2020
- 1. THE MANUFACTURED SOIL ENVIRONMENT Turning Specifications into Deliverable Soil Blends Kevin Donnelly CH Horticultural Soil Scientist
- 2. FINDING RESOURCES THROUGH EXTENSION • “mushroom compost” • 10,300,000 results • Sponsored product • 9 gardening site • 8 sales sites • Wikipedia, • 1 extension site • “mushroom compost extension” • 1,740,000 results • 16 extension results • 4 gardening related sites • www.e-gro.org
- 3. MANUFACTURED SOILS ENGINEERED AND MANUFACTURED SOILS DETAILS OF TESTING THE SOIL DESIGN PROCESS CURRENT RESEARCH INITIATINVES
- 4. LURIE GARDEN
- 8. TREE GROWTH LIMITED BY AVAILABLE SOIL 1-3CF SOIL FOR 1SQFT CANOPY
- 11. SILVA CELL
- 13. GREEN ROOFS
- 14. B I O S W A L E R A I N G A R D E N
- 15. PLANTING SOILS
- 16. WHEN CONTAMINATED SOIL • Growing Home Chicago
- 17. WHEN CONTAMINATED SOIL • Growing Home Chicago
- 19. LAB TESTING OF MANUFACTURED SOIL Capacity and Limitations
- 20. MATH LESSON #1: SMALL SAMPLE SIZE
- 21. FIELD TESTING Compaction Infiltration Moisture content Matric potential and plant available water
- 22. LAB TESTING • Hydrometer • Particle Size Distribution • Loss on Ignition % OM • Infiltratin • Porosity • pH • Nutrients
- 23. LIMITATIONS OF TESTING Excerpt from A&L Great lakes example report
- 24. REVIEW OF A GREENROOF TEST
- 25. DETAIL ON WHAT IS TESTED • Saturated Hydraulic Conductivity • Initial Dedia Density • Saturated Density • Max. Media Density • Saturated Weight • Water Retention • Dry Density • Total Porosity • Air Fill Porosity • pH • EC • Organic Matter • Particle Size Distribution (Percent Passing) • Soil Texture (Sand, Silt, Clay)
- 26. 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 0.001 0.01 0.1 1 10 100 PercentFiner(byweight) Diameter (mm)
- 29. Consistency Cost Availability Weight %OM pH Note Compost X X XXX XX 30-60% >7 Not a product but a process Topsoil X XX XX XXX 1-5% Variable but 5-8 Subject to random fields Pine Bark XX XXX XXX X >90% Low 4-6 Comes in different sizes that impact structure Sand XXX XX XXX XXX 0 High but not buffered Different sizes but most is torpedo sand( FA2) LWA XXX XXXX XX XX 0 High but not buffered Basis of most Green Roofs, expensive and logistical challenges. Shale/Slate or Clay Perlite XXX XXXX XXX X 0 Inert Not used much anymore in Green Roof, but very light weight Vermiculite XXX XXXX XXX X 0 Inert Can help slow down water green roof 5% Biochar X XXXX XX X >80% High >8 Expensive and not fully understood inconsistent from source to source, use 5-10% Worm Castings XXX XXXX XX X 30-60% >7 Consistent organic, but can be very expensive
- 31. WHERE DO SOILS COME FROM Webber Grill in Huntley
- 32. Soil Survey soil types WHERE DO SOILS COME FROM
- 33. WHERE DO SOILS COME FROM Wide variety of organic matter
- 34. MATH LESSON #2: DRY WEIGHT ARITHMETIC OM Dry Weight Pounds of OM blend Percent in Blend Lbs of final blend Lbs om in blend SAND 0% 1000 pcy 0 lbs 30% 300 lbs 0 lbs TOPSOIL 5%` 800 pcy 40 lbs 50% 400 lbs 20 lbs Compost 50% 400 pcy 200 lbs 20% 80 lbs 40 lbs Totals 780 lbs 60 lbs Blend percent OM 60lbs/780lbs 7.7% OM
- 35. MODELING WEIGHT AND WATER R² = 0.844 20% 25% 30% 35% 40% 45% 50% 55% 60% 50 55 60 65 70 75 80 85 90 WaterHoldingCapacity Saturated Weight Comparison of Saturated Weight and Water Holding Capacity. Like Mixes R² = 0.2179 20% 30% 40% 50% 60% 70% 80% 50 60 70 80 90 100 WaterHoldingCapacity Saturated Weight Comparison of Saturated Weight and Water Holding Capacity. All Mixes
- 36. TRYING TO MODEL OTHER VALUES R² = 0.5554 y = 0.0092x - 0.445 R² = 0.7083 R² = 0.7258 R² = 0.1277 R² = 0.7171 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 50 55 60 65 70 75 80 85 90 PercentPassing Saturated Weight Comparison of Saturated Weight and Percent Passing
- 37. CENTER FOR HORTICULTURAL SOILS TESTING AND RESEARCH (CHSTR) Research and Testing at Midwest Trading Plant Available Water Research https://hortsoils.blogspot.co m/
- 39. TEMPERATURE DATA
- 40. MATRIC POTENTIAL
- 42. THANK YOU KEVIN DONNELLY CH HORTICULTURAL SOIL SCIENTIST MIDWEST TRADING
Editor's Notes
- -welcome -Kevin Donnelly, hort soils scientist - I am Kevin Donnelly, horticultural soil scientist for Midwest trading. We are the non-plant side of the Midwest companies focusing on mulch and soil b
- Before I gets started, one of the challenges we face as an industry is that there is a lot of information online and it can be difficult to find reliable sources of information. If I am having issues finding any information I add extension to my search terms to get more focused results hobby. Gardening. As such there are a lot of opinions. So when
- So today we are going to look at the manufacted soil environment. I have been working with engineered soils for 13 years now and in the time I have today I wanted to share with you my perspective of sourcing, designing and testing engineered soils. Too often I find there is a disconnect between all the parties involved in these types of projects, so hopefully this will help shed some light.
- In landscaping there are a lot of situation where you try to amend the in place soil that is usually high in clay, compaction and low in orgaincs. Manufactured soils on the other hand are putting creating a landscape where there weren’t before. Take Lurie garden for instance.
- In this case it used to be industry and trains etc. Material was brought on site to create the landscape.
- One thing before we move on that is an important consideration for any type of project is that you don’t always have control over the outcome, even when you have really good plans. There is no way to check, this is materials that are buried out of site, so whose to say things were done
- So lets talk about the various types of manufactured environments. For the purposes of this discussion I have broken them down into strucrual soils, green infrastructure and planting soils.
- Looking at plant growth, one key element is the amount of soil available. This is most prominent in trees as shown here. The amount of soil available in the median area vs the larger planting area significantly influence the success of these trees.
- This concept continues when discussing Structural soils, These are there to provide support for paved surfaces and at the same time allow trees to thrive and not heave those surfaces.
- There are a couple of ways to address this problem of trees failing in streescapes. The first is CU structural soil developed by cornell university. This is a blend of rock, clay loam and a tackifier that allows for enough compaction to lay concrete over the soil, but still have proper void spaces and clay loam to provide room for roots system to grow underneath the paved area.
- Another is a silva cell which is essentially a vaulted sidewalk where regular planting soil is placed underneath for trees. Each system has a different way of addressing the same issue. The proponents of both often criticize the other as being insufficient or impractical, and both methods are costly compared doing nothing. But the benefits of trees reaching maturity in the streetscape can’t be over stated.
- So this is not a picture of green infrastructure, but it is the Stickney waste water treatment plant along 55. This is the largest waste treatment plant in the world. Now our sewer and storm water systems are combined and during heavy rain events, if the grey infrastructure systsm is over taxed, they start overflowing into the river, which is a problem. That is why the deep tunnel project was started in the mid 70s and will probably not be completed for another decade. That is designed to capture storm water and hold it until it can be processed. One of those pits is the thorton quarry which holds almost 8 billinon gallons of water.
- Grey infrastructure projects are big and costly and tree the outflow of the problem. Greenroofs, bioswales and rain gardesn on the other hand are small projcts that control the water at the source. During a 1inch per hour rain event, a normal roof all of that will go into the system. Greenroofs on the other hand will retain up to 70% of that water and slowly release the rest.
- Bioswales and rain gardens have similar activity by slowing the horizontal flow of water and help filter and percolate that soil back down into the ground water storage.
- Then there are planting soils which is somewhat of a catchall. There is a lot of variety when it comes to application and desired bend for planting soils. I have some examples of those as well as others we have talked about on the side. These can be at or above grade, so some greenroofs, like millennium park and lurie garden are more planning soils than a traditional greenroof
- There are a lot of considerations for choosing plating soils in a manufactured environment. Fore example, if there is contaminated soil as is present in a lot of urban communities, sometimes the best course of action is to put a barrier up as was done here at growing home in Chicago
- so they can develop a contaminant free organic farm
- So for engineered soils projects there is normally some sort of specification. This will spell out all sorts of things from plant selection and installation to clean up and getting paid. The soil portion can be all over the board. Sometimes it is a simple description in a drawing or be very detailed with submittal, testing and QA requirements. Unfortunately more often than I would like there are specifications that are unrealistic, incomplete or contradict themselves. One that comes to mind recently was a request that a requirement to have 1/3rd sand mixed with 2/3rd soil. The resulting blend was required to have less than 33% sand. The problem is that soil has portions of sand/silt/clay in them, so the requirements are mutually exclusive.
- While an issue worth discussing, for today I will leave it at that. Lets talk about the role of testing in engineered soils. There are a number of common tests and guidelines that are used. But the process of testing has some limitations that I will go over
- So for our first math lesson, we will bring in statistics and one of my favorite diagrams is the bell or standard normal curve. Briefly, the curve shows the incidents of different measurmeents of the same thing. The chance of a value falling in the first section is 68%. So say pH of peat for instance. You could say the average is 4.5. but there is a 64% chance of getting a perfectly acceptable value of 4.3-4.7. Then a 95% chance of getting a value of 4.1-4.9. So the challenge here is we often assume that the one test we run must be the average, but in the example of peat, that one could just as easily be 4.8 is it could be 4.2. Now we could simply test more samples, but there is a cost of time and money. The cost and turn around time can be high and most project customers would not want to spend the money to run that type of testing.
- So what is the ultimate test. Well plant growth and success for sure. But aside from that, field test are a good gauge of soil performance. We can test percolation to see how a soil will drain, measure compaction as well as some sensors designed to measure soil moisture content and matric potential. These two combined can help establish plant available water which I will go over at the end. These are great for all sorts of natural soils, but can’t be done prior to a job going in.
- So there are lab tests that have been developed. The key probable here is they are developed for natural soils, and there can be some challenges when using those methods for loose engineered soil. Organic matter is tested through LOI by burning off organic matter at high temperatures. ASTM has adapted the German FLL methods for testing the dead load of a greenroof in the lab. Others include pH, EC, nutrient content as well as a lab method for infiltration of Ksat, but again this was developed for taking cores out of natural soil, so compacting a loose soil into them can pose challenges. They hydrometer for testing sand silt and clay has similar issues. It is most consistent with low organic natural soils. When we start adding compost to these blends, the methods need to be tweaked to provide more reliable results.
- The purpose of testing is to predict an outcome, so all tests that are developed need to tie back to predicting if the desired landscape system will function. The challenge is that most were developed for agricultural soils to predict crop growth and yield. Many of the nutrient recommendations that labs provide are geared towards specific crops like corn and beans or turf and may not be the best course of action for landscape projects. Some publications online, even through extension may be focused on specific plant types. The recommendations for EC on annuals is not for instance applicable to growing trees.
- Aside from sol there are a number of materials that are used in engineered soil blends. There is more variability in greenroof applications than planting mixes but here is a list of some we come across regularly and some very rarely.
- For starters when talking about mineral soil, these come from large scale development. When land is cleared for a subdivision or commercial property, they push topsoil up into a pile and someone comes in with a pulverizer to process and sell that soil. The type of soil is random. Good news is we sit on some of the best soils in the world, and the majority of soils we run into are silty clay loams, with some pockets of sandy soils. Pretty much the only thing we can do to modify the texture (sand silt clay) is add sand. So if we start with a soil that has 50% silt and too much clay, to hit the CDOT planter soil spec of >45% silt, there is a narrow window to lower clay but maintain silt content. If you have access to only sandy soil. Then there is no hitting that spec. The same is true for structural soil. The spec calls for >20% clay. In SW Michigan and other parts of the country, there is not clay soil and it has to be trucked in to hit that specification. The fields themselves can vary as well. This is an image of the weber grill site just off of 90 and 47. We were pulling from this field years ago, and different areas of the field had drastically different organic matter contents. The trouble we as providers can’t go in and say we only want the high OM silty clay loam soil. The GC doesn’t care, and just does what is efficient for them. Additionally when there is a pile, and a road needs to go in that area, the pile is spead across the property and that source is done. During the recession we would be in 6-7 small fields a year and having a soil available for a job 6months out was not possible. Lurie garden is an example of when there happen to be a large source of sandy soil near Kankakee that worked and could be relied upon. Some of these bigger projects may stumble upon a source that is reliable, but more often than not, you risk not having the material. The weather also plays a role as frozen and wet prevents it from being processed.
- Moving on, so math lesson two. This is actually a bright spot in blend design. Since organic matter, PSD and texture are weight based measurements, ifyou know the dry bulk density and in this case organic matter of each component, you can mathmatically estimate the outcome of a blend. Materials vary, so this is not perfect but it gets you close. In the example we can see by adding 20% compost to soil and sand, we can get an estimated blend organc matter cont3ent of 7.7%.
- That’s the easy stuff. More difficult is water predicting the structure and porosity of the blend. This is where trial and error come into play. We have general ideas of how infiltration, WHC and air poristy will play out, but it is very difficult to model. Here is an example of some greenroof data where the trend is pretty clear on when it holds more water it will weigh more. But when you start to look at other types of mixes that are not aggregate based, that trend starts to fall apart. Looking at PSD and saturated weight for instance and there is not a strong trend, so it is guess work.