13 Soil Mistakes to Avoid
Soil Mistake #1: Creating Dispersion
First, what is dispersion? Dispersion is when clay particles are kept separate from one another like opposite ends of a magnet.
In fact, clay particles are very similar to the negative ends of a magnet. Certain minerals bring clay particles together (with their positive charges). Others keep them repelled.
Flocculation is the opposite of dispersion.
Flocculation is the process where individual clay particles are pulled together. This clumping is called AGGREGATION. Soil aggregates are cemented clusters of sand, silt, and clay that create pore space in the soil—allowing water movement and air exchange. THIS is one of the most important keys to healthy soil.
Dispersion creates terrible soil structure. So how does it happen?
1. Dispersion/Flocculation is a purely chemical phenomenon, driven by the balance of cations in the soil. Calcium has a very high flocculation power, while sodium and potassium cause dispersion. The general balance between Ca and Mg compared to sodium is what determines flocculation/dispersion. Too much sodium—from the use of toxic fertilizers, over-application of compost, or the use of poor irrigation water—will cause dispersion. Alternatively, too little calcium may be the issue, making soil testing and mineral amendments of utmost importance in low pH soils!
2. Electrical conductivity influences dispersion as well. EC is simply a measure of the total ions in the soil solution. Low EC increases dispersion. Low EC, high sodium soils are considered SODIC and are HORRIBLE for soil health.
Don’t create sodic soil. Be careful with what you apply.
Get a soil test and balance the cations.
The Soil Food Web is great but short-sighted. Biology is not the only thing that matters.
Don’t ignore your soil’s physical structure. It’s SUPER important.
Soil Mistake #2: Overshooting pH with Minerals
There is one simple thing you can do that will throw your soil out of balance for years. It will reduce your crop health, cost you money, and cause numerous issues in production.
It’s the over-application of fertilizers and minerals that raise pH. The result of an elevated pH is deficiencies of trace elements such as iron, manganese, zinc, boron, and copper.
The biggest culprits are Ca, Mg, K, and Na. While any mineral can create a severe issue, these four, in particular, will cause serious tie-ups of other minerals. Often for years and years with little way to mitigate the situation.
It’s an easy mistake, really. Applying 3,000 lbs per acre of lime vs 1,000 lbs. Applying lime instead of gypsum. Apply way too much high-K compost. Or when seeking magnesium, using dolomitic lime instead of magnesium sulfate.
Plant deficiencies are often CREATED by growers due to the over-application of other minerals. If you need help with a soil interpretation, order one here.
Soil Mistake #3: Applying the Wrong Source of Calcium
Don't apply the wrong calcium source. Don’t guess. Seek help or risk imbalancing your soil.
As calcium is possibly the most important mineral, this is an important mistake to understand.
It’s confusing to know when to use each of the most common calcium sources. Here are the Cliffs Notes:
Ag Lime should be used when you need calcium and the pH is BELOW about 6.2.
Dolomitic Lime should be used when you need calcium and the pH is BELOW about 6.2 AND you also need magnesium.
Gypsum should be used when you need calcium and the pH is ABOVE 6.3. (There are other uses for gypsum, but these are the Cliffs Notes.)
The longer answer is this…
Agricultural lime is recommended when calcium is needed, the pH is BELOW 6.2, and no magnesium is needed. The quantity recommended varies based on the total CEC, the calcium deficit on the standard test, and the maximum one-time application limit.
Dolomitic lime is recommended when calcium and magnesium are needed and the pH is BELOW 6.2. The quantity recommended varies based on the total CEC, the LESSER of the calcium and magnesium deficits on the standard test, and the maximum one-time application limit.
Gypsum is recommended when a soluble source of calcium is needed, or when there is a cation imbalance, or when the pH is too HIGH for lime. The quantity recommended varies based on TCEC, the calcium deficit on the standard test, and the calcium solubility in the soil solution.
(There are always exceptions: if you are no-till, your calcium is under 60%, or you have a calcareous soil!)
Soil Mistake #4: Using Too Much Compost
I’ll admit it. I don’t love compost half as much as the average person.
Building soil DOES NOT MEAN adding compost every year.
Just because a grower says: “I use compost every year and my crops are very healthy” doesn’t mean their program applies to you. (It also doesn’t mean their crops are nutrient dense, or pest and disease resistant, or resilient to environmental stress.)
All composts are different. The feedstock and production process determine the mineralization of compost. Composted chicken manure is often 3-5-2, while composted yard waste is 1.25-0.8-1.2. That is a FIVEFOLD difference in the case of phosphate.
Both the differences between compost as well as the complexity of their mineral profile make it very easy to over-apply minerals and create imbalances in your soil! While compost brings the whole gamut of minerals, potassium, sodium, phosphorus, and nitrogen are most commonly over-applied through excessive compost.
Therefore, only apply compost when sodium is low, and you need N, P, AND K. Apply enough to fulfill the lesser of the three requirements, and fill the void of the others with another mineral source!
That said I admit that compost is a magical tool. It is a biological POWERHOUSE. It adds a valuable organic food source for microbial life. It can improve soil conditions and give your plants a chelated source of both macro and trace minerals. A fine dusting applied in the spring is a tremendous inoculant and source of organic carbon. When you see the opportunity to use it…DO IT! Just don’t overdo it.
Soil Mistake #5: Large Applications of Nitrogen in the Fall
This one might be controversial.
The key to regenerative farming is carbon.
The second biggest threat to soil carbon is NITROGEN. In general, nitrogen has the power to degrade soil carbon significantly.
Fall nitrogen applications degrade carbon. They are one of the worst things we are still doing on an annual basis.*
Nitrogen immediately begins feeding microbial digestion of residues, oxidizing organic matter, and releasing CO2 into the atmosphere. It narrows the C:N ratio - shifting the biological profile among other things. And for what? There aren’t crops growing in the fall and winter!
Nitrogen is quickly converted from ammonium to nitrate in the soil. Fall applications allow six months of time when that nitrate can leach out of the root zone and into groundwater, especially in places with a lot of winter precipitation.
It makes no sense. Wait until before planting when your crops actually need that nitrogen. And better yet, don’t apply a single pound of nitrogen until a tissue or sap test justifies it!
*Complex sources of nitrogen that require time to decompose and release are MUCH better.
Soil Mistake #6: Focusing on Water pH and Ignoring Alkalinity
If you irrigate your crops (practically everyone), you need to know this.
Alkalinity has a WAY bigger effect on soil than does the water’s pH!
Water with high alkalinity (alkalinity = high levels of bicarbonates or carbonates) always has a pH value 7 or above, but water with high pH doesn't always have high alkalinity. This is important because high alkalinity exerts the most significant effect on soil and plant nutrition.
(Don’t totally ignore water pH, though. Water pH is still important for crop management because it affects the solubility of fertilizer. The higher the water pH, the lower the solubility of these materials.)
The solution to high alkalinity is to neutralize it by adding a strong mineral acid to your irrigation water (usually sulfuric acid or phosphoric acid). All of the alkalinity has been neutralized when the pH of the water reaches 4.5. (Usually going down to around 6 will take out enough to improve things dramatically.)
*NOTE: when you “pH” your water, you are often adding significant nutrients to your water.
Soil Mistake #7: Reducing Your Available Phosphorus Through Lime
The fastest way to loose your available phosphorus is to add loads of lime. Why?
Phosphorus in soil is an anion with a triple negative charge. If phosphorus goes into the soil and doesn’t quickly bind to organic matter, it will bind with calcium, iron, or aluminum and become completely insoluble in your soil.
It is estimated that around 75% of applied phosphorus fertilizer is locked into the soil mineral matrix becoming plant unavailable. The acids exuded by roots and biology are strong enough to break free some of this phosphorus for the plant, but not enough.
Be aware that applying large quantities of lime all at once will reduce your available phosphorus significantly. Consider applying a phosphorus source in conjunction with lime to mitigate this problem.
But be sure to apply the RIGHT phosphorus source for your soil! (For example, soft rock phosphate won't release its phosphorus in a high pH environment very quickly. I personally don’t recommend soft rock phosphate when the pH is above 6.5. There are better sources.)
Soil Mistake #8: Tilling to the Same Depth Every Year
Do not till to the same depth year after year.
Why exactly is this a problem?
It can create a hardpan layer that prevents water infiltration and root penetration. It can cause major issues.
How big of a problem is it?
It depends. The best way to determine the existence of a hardpan layer is with a penetrometer.
Push the penetrometer into the soil in as many places around your farm as possible. Push with consistent pressure, and when you see the PSI reading consistently skyrocket at a certain soil depth you know you have a hardpan.
If you really want to dive deeper, perform two more tests at this layer:
1. Do a separate soil test only at the depth of the hardpan. Do this by gently digging/scraping away soil above the hardpan and only test the area at the hardpan. Higher sodium, nitrogen, sulfur, and other mobile minerals will indicate that you have a drainage issue.
2. Dig down to this layer and perform a water infiltration test. See if the infiltration rate differs from the top of your soil, indicating drainage issues.
Soil Mistake #9: Balancing Your Soil but Ignoring Biology
You can have perfectly balanced soil but still have MAJOR problems.
Just because minerals show up on a soil test DOES NOT mean they are available to your plants. In theory, standard soil tests extract minerals using laboratory acids that approximate plant and biological acids. But it is still very crude.
Other things that influence availability are: temperature, moisture, biological activity, oxidation/reduction potential, and aeration, to name just a few.
Biology is a HUGE one.
The other variables explain why the SOLUBLE PASTE TEST is so important. This test gives you a sense of what is available in the soil solution. It lets you see where availability issues are happening.
For example, I frequently see high phosphorus on a standard soil test, but low solubility in solution. (One solution here would be phosphorus-solubilizing bacteria, or practices that promote mycorrhizae, a powerhouse when it comes to phosphorus availability.)
The point is this:
1. Never neglect the task of creating a healthy biological environment in your soil. If you do, your soil test will become increasingly inaccurate because your applied minerals will never be available for the plant.
2. Get a soluble paste test to see where availability bottlenecks are happening in your system! More information is always better.
*Pro Tip: Send in a small bottle of your irrigation water when getting a soluble paste test, and have them run the test with it instead of distilled water.
Soil Mistake #10: Balancing Ammonium and Nitrate in Your Soil
There is a MYTH that will inevitably lead to over-application of nitrogen.
I’m not sure where this myth developed, but I've heard that it's ideal to target equal parts nitrate and ammonium in the soil.
This is foolish.
When any ammonia-heavy amendment is applied, it is converted to nitrite, then NITRATE in a relatively short period of time (usually a few weeks). It is an inevitable chemical process, explaining why the vast majority of time soil tests show much higher nitrate than ammonium.
If you see low ammonium on a soil test, and add more, it will push your total N up further. When you test again, you’ll see low ammonium and add more again. This will ultimately lead to nitrogen over-application and less resilient crops.
This plant is getting crushed by powdery mildew. PM loves high-N environments. So do aphids and many other pests.
Nitrogen application should be determined by your crop requirement, your existing organic matter, the time of year, and the amount of nitrogen already in your soil (determined by a soil test). I like to go further and use sap or tissue analysis.
Soil Mistake #11: Ignoring Trace Minerals with High pH Soil
If your soil pH is above 6.5, knowing this can dramatically improve your crop health.
Do not ignore trace minerals in high pH soils.
Iron, manganese, boron, copper, and zinc are ALL less available in high pH soils.
I used to work in calcareous Colorado soils, where iron chlorosis and manganese deficiency are very common. With so much excess calcium, many trace minerals are tied up and completely unavailable to the plant.
When the pH reaches 7, I would suggest starting to foliar all the trace minerals. Adding them in fertigation may work, but they will surely become tied up and unavailable in time.
Soil Mistake #12: Stratification
If you are applying minerals, you MUST be careful of stratification.
Certain minerals are not soluble – lime and soft rock phosphate are two very common ones that come to mind.
If applied but not incorporated into the soil, these minerals can build-up and form a layer in the soil.
In the case of lime, this layer—usually in the top 1” of soil if you are an orchardist or no-till—will create a high pH environment and reduce the availability of P, Fe, Zn, Mn, Cu, and B.
This will create WAY more issues than you started with, especially because plants feed primarily in the top 6” of soil. It can create a problem in your soil environment.
A better way to apply these minerals (if you even need them) is in super small quantities every year—ideally just a couple hundred pounds of lime per acre. The minerals will slowly work their way down into the soil profile through mass flow as a result of water percolation. If your spreader doesn’t allow you to apply only a few hundred pounds per acre, wait until your pH drops below 5.8 or so. At that point, apply one application of the minimum amount your spreader can apply. Most importantly, keep tracking your pH change year by year!
I have developed a calculator to determine lime application rates based on your TCEC and organic matter.
Soil Mistake #13: Leaving Your Soil Bare
If you own land, this is the fastest way to drain the value of your long-term soil asset, with ONE caveat.
The Mistake: leaving your soil bare for any period of time
Leaving your soil bare is almost always bad news:
1. It increases erosion through runoff and blowing
2. It can reduce soil biological activity
3. It reduces your organic matter
4. It increases moisture loss
5. It increases weed pressure
6. I’m sure this list could go on and on…
*Caveat: I once heard a peach orchardist present a dry-farming technique that allows a crust layer to form on bare soil to conserve water during the season. The crust limits evaporation from the soil. It is critical not to break the crust with equipment or walking, otherwise, moisture will be lost! It blew my mind and I am open to it being an exception to this rule.