By Erin Marissa Russell
Do you know whether your property has caliche in the soil? If it does, you’ve been unfairly disadvantaged thus far in your gardening career. Caliche makes every part of a gardener’s work more difficult, and it’s next to impossible for plants to flourish in this troublesome type of soil. If you live in places like New Mexico or Arizona, you’re probably well familiar with it.
As a gardener, you should be aware of exactly what caliche is, how caliche in the soil affects your ability to grow plants, and how to diagnose whether your soil contains caliche. Luckily, we’ve got you covered with all the vital information gardeners should be armed with so they can identify caliche in their soil, then take action to reduce the caliche present in their garden.
If caliche has been a trial in your garden, you can use the tips in this article to break up stubborn layers of caliche and improve the soil on your property. With the caliche issue addressed and your soil newly upgraded, you’ll be able to get back to the reason you garden in the first place—collecting, cultivating, and caring for plants—with an exponentially higher chance for success with just about any plant you choose to grow.
What Is Caliche?
Caliche (pronounced as “ka-lee-chee”) is a notoriously difficult type of soil to work with that develops when lime, also called calcium carbonate, builds up in the ground. Gardeners working with caliche will soon discover that, without amending the soil or otherwise improving it, it’s practically impossible to grow anything in caliche.
Properties that have caliche soil are such a challenge for gardeners because the calcium carbonate deposits have welded the soil particles, which were once individual grains, together into something closer to a sheet of solid rock. It’s like trying to grow in cement!
As most of us know, bare rock is a chore to break up or dig into, and you can’t plant seeds in a stone—nor can a plant’s root system find the stability, water resources, and air supply the plant needs to thrive in a layer of rock. While caliche is technically a very hard and solid soil and not actually classified as rock, caliche certainly resembles rock, and it’s just as difficult to build a garden on caliche as it would be to grow plants on a stone. And like rock, caliche can be literally impenetrable, making it pointless to even attempt to establish a lush, green garden in caliche.
How to Tell Whether Your Soil Contains Caliche
If you’ve suspected you may have a black thumb because plants refuse to thrive in your garden and your soil has been a challenge because it doesn’t retain water well, has poor aeration, and is practically impossible to get a shovel into, there’s a good possibility that you can blame some (if not all) of your gardening woes on caliche. The list below will give you some key traits of caliche that you can use to diagnose whether your soil is caliche or not.
- If your soil contains caliche, you may struggle to till or dig into the ground, whether you’re using your hands or a tool like a shovel, spade, or hoe. Caliche can range from very firm, densely packed soil to layers so fused together that they form impenetrable stony sheets.
- Because caliche is more solid than the ideal garden soil, which has a fine, grainy texture, water cannot drain effectively through patches of caliche. Instead of water soaking deeper into the ground where it will remain to hydrate plants, water applied to caliche may drain slowly or fail to drain at all, resulting in a waterlogged surface or pools of standing water.
- Due to the poor drainage mentioned above, salt tends to accumulate in caliche soil.
- If your caliche is pliable enough for plants to be established at all, the roots of plants in your garden will be shorter and smaller than the plant’s ideal root system should be because the depth the roots can access is limited by the caliche’s solidity.
- Is caliche soil alkaline or acidic? Caliche tends to have a more alkaline pH level than is optimal for gardening. The caliche’s alkalinity can prevent plants from being able to take in the nutrients they need to survive.
Tips for Improving Caliche Soil
Make your soil more acidic to offset the challenges of gardening in caliche.
Acidifying soil that contains caliche reduces the soil’s pH level and makes it much easier to successfully grow plants with the soil you have. To increase acidity, you can amend your soil with elemental sulfur or manufactured soil amendments that contain elemental sulfur. If you prefer not to use elemental sulfur, you can increase the acidity of your soil and lower the pH level by amending with aluminum sulfate instead.
Aluminum sulfate has greater solubility than elemental sulfur, and its greater solubility means that aluminum sulfate gets results faster than elemental sulfur treatment. However, elemental sulfur is more affordable, and the savings increase along with the size of the area you’ll be treating.
These treatments work because bacteria present in your soil will produce sulfuric acid from the aluminum sulfate or elemental sulfur. The sulfuric acid generated by the bacteria will actually dissolve areas of caliche in the ground, leading to drastically improved soil texture, increased air circulation in your soil, and enhanced water retention—all of which add up to better soil health in general and increased likelihood of success with your plants.
While professionals sometimes use sulfuric acid to acidify soil (especially the soil around established trees), home gardeners should not consider using sulfuric acid in their gardens. Sulfuric acid is quite literally battery acid. As one would imagine, using battery acid as a soil amendment comes along with substantial dangers. The risks associated with using sulfuric acid on soil make this treatment one that’s best left to the professionals.
It’s best to use acidifying soil amendments before planting anything that might be sensitive to the necessary treatments. Ornamental plants used in landscaping are especially likely to be affected negatively when you treat soil to increase its acidity and lower the pH level, but many other types of plants can be sensitive to acidity, too. You will need to look up information on the acidity tolerance of the specific varieties of plants you are cultivating before deciding to use an acidifying treatment to be sure you will not damage your plants.
If you choose aluminum sulfate to acidify your soil, you’ll need four to six pounds of sulfate to lower the pH level by one full point (for example, from 6.6 to 5.6) when you’re treating soil with a fine or medium texture. (Note that about two cups of either aluminum sulfate or elemental sulfur makes up a pound.) If you’re using elemental sulfur on your soil, you’ll need one sixth less soil amendment than if you use aluminum sulfate. Refrain from adding any new plants to your garden for at least a month after acidifying your soil, or you risk burning the roots of the new addition to your collection.
If plants sensitive to acidity are already growing in the soil you wish to acidify, you can use a different method to administer the amendments. Instead of mixing the treatment into the soil, you can use top dressing to apply the products instead. For an average landscape plant, top dress by lightly mixing the sulfur or aluminum sulfate with the soil near the plant in repeated monthly treatments until the total amendment applied equals either two cups of aluminum sulfate or one third of a cup of elemental sulfur. Water thoroughly after application to help the treatment stay in position and begin to soak into the soil.
It will take time for the acidifying treatments to take effect, but you’ll need to test the soil’s pH level to determine how effective the amendments were. Do a pH test three months after each individual treatment so that you can stop amending the soil once the pH reaches your desired level. Some soils are particularly stubborn, so you may need to treat a few times before seeing meaningful results in those cases.
Avoid using lime if you have caliche soil. Lime makes soil more alkaline, so it will just make your problems worse.
Choose fertilizers that will support soil acidity to preserve the effect of acidifying treatments.
While a fertilizer alone is unlikely to substantially change the acidity of your soil, there are some fertilizers you can opt for that can supplement your acidifying treatment to help maintain the acidity level you want. Nitrogen fertilizers that contain ammonium sulfate or urea will be useful in helping you maintain the acidifying effect of the elemental sulfur or ammonium sulfate treatments we explained in the previous section.
If you want your fertilizer to work toward maintaining acidity, be sure to choose a nitrogen fertilizer that contains ammonium sulfate or urea. Other types of fertilizer, such as potassium sulfate or gypsum fertilizers, will not help support acidifying treatments like nitrogen fertilizers that contain ammonium sulfate or urea do.
Working in peat moss or pine needles before planting slowly increases soil acidity for gardeners that do not need to rush the acidifying process.
Peat moss or pine needles added to your soil periodically will both enrich the soil with an organic source of carbon while simultaneously working to lower the pH level of your soil. To use, spread a one-inch or two-inch layer or peat moss or pine needles over the surface of the soil, then mix the peat moss or pine needles down into the top six to 12 inches of earth.
As with other treatments, allow about three months for effects to take hold, then test your soil’s pH level to determine how effective adding peat moss or pine needles has been. Be advised that this acidifying technique works rather slowly, and it may not be possible to drastically increase soil acidity using peat moss or pine needles without also using a more powerful method for acidifying your soil (such as the elemental sulfur or aluminum sulfate amendments we discussed in the first part of the Tips section in this article).
Don’t depend on purchasing new soil to resolve problems with caliche in your garden.
It’s common for gardeners who have caliche on their property to attempt to resolve the issue by simply purchasing a truck full of soil. But when you order a batch of dirt, what you’ll usually receive is likely to be sandy loam instead of the rich, fertile, garden-ready soil you hoped you would get.
Sandy loam is not optimal for use in gardening because it often dries out and hardens with time. Once this transformation is complete, you’ll be right back where you started—stuck with plenty of soil that’s practically useless for gardening, kicking yourself over the wasted expense and work you devoted to that truckload of sandy loam, and bitter over your empty garden and the plants you lost along the way.
For these reasons, we’ve recommended that you work on improving the soil that’s present on your property even when it contains caliche instead of simply replacing your current soil with purchased dirt. Save yourself the wasted time and heartache that come along with this expensive lesson, and focus on developing soil your plants can thrive in from the get go.
If you were unfamiliar with caliche until now, this article may have identified the cause of gardening challenges you’ve struggled with for quite some time. Or perhaps you’ve known that your property’s caliche soil was a problem all along. Either way, the tips we’ve presented for improving your soil will allow you to wipe the slate clean and forget that caliche ever caused you so much trouble and stress.
Once your soil has been transfigured from infertile caliche to new and improved garden soil with excellent texture that retains plenty of water for your plants while offering plenty of drainage, your garden will be revolutionized along with the ground underneath it. Most importantly, your days of hacking away at rock-hard caliche will be over—so choose one of the tips we suggested to start with, and take the first step toward your garden makeover today.