Class: Understanding Front Range Soils

“Soil is precious and we treat it like dirt.”

This class was taught by Jean Reeder, Ph.D. soil scientist. She spent 30 years with the USDA ARS, the agricultural research service. Since retirement, she is now a consultant for the CSU Soil Testing Lab and she is one of the instructors for the Colorado Master Gardener program. She has also discovered that she didn’t really understand the soil in her own back yard. Of natural, agricultural, and urban soils, urban soils are the most complex and the least understood. She has begun applying her skills to changing that.

Anyone who lives in Colorado knows that we face a lot of challenges. Our semi-arid climate is cool with a short growing season, dry, and highly variable in both temperature and precipitation. However, more than 80% of plant problems are because of the soil. It is the fundamental component of the landscape. That makes it the biggest challenge. However, it is also the least understood. We have even less information to go on than most of the country, as our soil is as different as our weather. Where most soil is more acid, ours is alkaline. If you find a native soil around here that is 2% organic matter, you’re doing really well. In Iowa, 6-7% organic matter is perfectly normal. We also have free lime. She told us about one woman she knew that preferred to send her soil samples to a lab in Missouri to be tested. They never tested for free lime, since it isn’t an issue in Missouri.

There were a few main points I got from this class. The first is, test your soil. The old saying is “feed and nurture the soil and the soil will feed an nurture the plants.” That’s true, but how do you know how to nurture it if you don’t know where it is now? Sending off samples for testing is a bit more expensive than picking up a soil test kit at the store. However, you get a lot more information and a lot more accuracy. The other thing is to get it tested locally. I use the CSU service. Granted, the lab is in Fort Collins, which is not exactly around the corner from Colorado Springs, but they know Colorado. They know about free lime and our increasing problem with salt in our soils. They can tell me how to manage it in a way that will work here. The kits you can pick up at the store are apparently usually calibrated for acidic soils, which makes them worse than useless in our alkaline soils. They also don’t come with instructions for fixing any issues you have.

Once you get your test results back, there are a couple of things that it is best to just make peace with. The pH and the texture are almost impossible to change, and any changes may have other consequences. Our soils tend to be more clayey. One apparent solution is to add sand. Aside from the fact that you have to add too much sand for that to be practical, the recipe for concrete is lime and sand. It’s not a guarantee, but if you’re unlucky, you might end up with a concrete slab where you had intended to put in a garden. As for pH, our soils are very well buffered, so they resist being changed. One possible change is to add sulfur. However, if you have a high-calcium soil (lime is usually calcium carbonate), you end up making gypsum. Gypsum is used in places as a fertilizer. However, it is a salt, so you will be increasing the salt content of your soil. The only way to change the pH with any hope of permanence is to manage the garden correctly and consistently for about 50 or 100 years or move to the mountains. There are some old gardens and gardens in the mountains that are slightly acidic. However, those are the exception not the rule.

The result of squished roots and a rough spring.

Now that you have made peace with your texture and pH, it’s time to talk about amendments. All amendments are not created equal. In fact, all compost is not created equal. We do not have naturally saline soils. However, the application of high-salt fertilizers, both organic and not, is turning salt into a problem. There’s a reason people used to salt the fields of their enemies. You can’t grow anything in salted soil and, unless you have massive amounts of high-quality water to flush the salts through the soil layers, it is almost impossible to fix. She did a study of bagged, commercial fertilizer. However, it never got published because the only consistency was that animal-based ones had very high salt content and plant-based ones tended to have merely high salt content. Other than that, there was no telling what would come out of a particular bag. Even if you go natural, there is still a huge variation in what you can get. She showed us numbers of actual fertilizers she had analyzed from non-bagged sources. The numbers were all over the place. Including two that ended up with toxic amounts of trace minerals and several that were going to cause salt issues if they were used with any regularity. If you are considering using your neighbor’s horse manure, she mentioned that what they are fed affects the quality of the manure. The quality of what goes in affects the quality of what comes out the other end. Think about that for a minute. I sure did.

This one isn’t too happy with it’s placement either.

The last major point is compaction. I have run across this as being a problem in gardens before, but she took it to another level. Compacted soil means that the aggregates in the soil, the structure made from the mineral content and the organic material, have been destroyed, which means that there are few if any pores in the soil for air and water to penetrate. If you live in an urban area, it’s best to assume that your soil is compacted. If you are able to do so, you will want to fix that before you put down lawn and gardens, as it is almost impossible to fix later. If your soil has no, or few, pores with air and water, roots will not have anywhere to go, or a reason to go there. The smaller and more restricted a root system is, the smaller the above-ground part of the plant will be. I have notice small trees in “hell strips” between the sidewalk and the road recently that are only leafing out on their lower branches. This is apparently a result of restricted root growth combined with a dry spring. The upper branches had to be sacrificed because the limited roots couldn’t support them in the rough conditions we have had this spring. If it wasn’t trapped between the compaction under the road and the compaction under the sidewalk, the roots would be able to spread out, giving them half a chance to support the growth that had gone on before conditions got bad. When you walk across wet, loose ground once, you just compacted that ground by 75%. If you walk across it four times, now it’s 90% compacted. Now think about the damage a bulldozer or crane will do while the house is being constructed.

The overarching concept from this class is that, with two exceptions, less is more. On average, it takes about 150 years to build an inch of topsoil in nature. Colorado would need more time than average. Therefore, taking 10 years to slowly build a to-die-for garden is still well above average. The fewer amendments you use, the less likely you are to make a mistake. If you salt your garden or add toxic levels of a nutrient, you will be spending a lot of time and money to fix it. Along the same lines, once our native soil has been disrupted, she let me know that it is very hard, very expensive, and often heartbreaking to restore it. The less of the native landscape we disrupt, the less we will have to painstakingly restore. Tilling and other machines tend to break up soil aggregates, affecting the soil structure. Hand-digging is far less likely to do so. What we need more of is patience and knowledge, hence the slightly lengthy post. Your soil is unique. The more information you can gather, and the more time you can spend with it, the better equipped you will be to know how to nurture it.

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2 responses to this post.

  1. Hi Cattaillady!
    The silt left by cattails in the marshes appears to be a very good partial replacement for the soil that is lost each year to erosion, etc. There really is a huge amount of it available worldwide. Other aquatic weeds leave fertile silt, too, and it coats lakebeds and streambeds until they are out of contact with the underground water they should replenish. This is a major part of climate degradation. Look at Africa’s Lakes Chad and Victoria. In Chad, it is cattails, in Victoria it is water hyacinth. Cattail sloughs that should be lakes are a large part of what causes America’s dustbowl.

    Steve

    Reply

    • I will absolutely look into that. Thank you! I guess that’s just one more thing that cattails can be used for, although I am curious now what is causing the filtering plants to be separated from the water they are supposed to filter.

      Reply

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