The Gypsum Antidote
A recent article in the Farm Journal’s Ag Professional Magazine titled “The Gypsum Antidote” outlines the benefits of gypsum applications in combination with manure applications. (Note that the picture of the applicator is Soil Solutions’ floater.) Below is the link to this article.
A misunderstanding about lime and gypsum is that if you mix them or apply them together they will be antagonistic or “fight” one another. Another misunderstanding is that gypsum is for high pH soils and lime is for low pH soils. In actuality, gypsum can be applied and has benefits in both high pH soil and low pH soils. Gypsum and lime applied together can actually have synergistic effects.
So why would we want to apply gypsum and lime together? I will outline several reasons.
First lime is insoluble in water so it is relatively immobile in the soil. Contrast that with gypsum which is water soluble and has much greater mobility in the soil. Gypsum therefore improves soil conditions much more rapidly than lime and will affect soil conditions to a greater depth than lime will. Gypsum will supply calcium to deeper depths than lime. This will improve subsoil conditions, and allow for greater root growth (better nutrient and water efficiency). If aluminum toxicity is an issue due to acid subsoils, the gypsum will also react with the aluminum to offset its effect. As a result, root depth will be greater and nutrient availability will be improved.
Lime can initially cause a cementing of the soil at the surface decreasing water infiltration. By applying gypsum with the lime you will negate this surface sealing affect. With improving soil conditions, lime movement will be greater.
Lime will have a much more pronounced effect on soil pH than gypsum will, however, the pH change will be near the surface where the lime is placed.
Lime is often times dusty and can become air borne when applied. The most reactive lime is the dust so you will not realize the benefits of this lime if it lands on your neighbor’s field. By applying gypsum with the lime you can apply a very high quality lime source and control the dustiness of the lime. The application will be dust free.
If you have variable soils and areas with high pH you won’t want to apply lime in those areas, but still may want to apply gypsum. In those situations, a mix of lime and gypsum may not be ideal.
Applying lime/gypsum mixes are becoming more common by our customers. A 50:50 lime/gypsum mix is most often used in our area. Typically, the rates of each product are 1000 or 2000 pounds per acre.
Should there be an efficiency factor for granulized gypsum when compared to PRO CAL 40? Over the years we have frequently gotten this question. One reason is when comparing granulized lime and agricultural lime it has been common to use an efficiency factor. All liming materials are based on an ECCE (Effective Calcium Carbonate Equivalent). This value is expressed in either % of a ton or pounds and is based on particle size and purity. The more pure and the smaller the particle size the higher the ECCE value and the faster response you will see. The efficiency factor for granulized lime is assuming that it has a higher percent in the smallest particle size. Although most agricultural lime contains some in this smallest particle size also, these small particles could become air borne during application and not land on your field.
What about gypsum? There is no such value as an ECCE, but in effect, the same holds true for gypsum. The more pure the source and the smaller particle size gives you the most value and the fastest reactivity in the soil. Therefore, a laboratory analysis of gypsum evaluates these two factors also for effectiveness. There is some mined gypsum on the market that is quite course.
So getting back to our original question: Should there be any efficiency factor for granulized gypsum products when compared to PRO CAL 40? The short answer is “no”. PRO CAL 40 is one of the most pure forms of gypsum you can buy and the particle size is very small (<160 microns) so granulized gypsum has no advantage over PRO CAL 40 other than it can be spread at lower rates easier and can be mixed with other granulized fertilizer materials. Since PRO CAL 40 is less than $20 per ton and granulized costs more than $150 per ton, PRO CAL 40 is by far, more cost effective as a soil amendment, hands down!! To improve soil conditions, higher rates of gypsum (>1000 pounds/acre) need to be applied, making PRO CAL 40 the product of choice.
What Difference Does it Make?
This statement has been made famous by one particular politician, but farmers sometimes ask this question about various aspects of fertility and crop management. One of the areas that are overlooked is the importance of having soil conditions that provide for good root growth. Out of sight….out of mind is often how soil is treated. The picture to the right shows roots that are growing laterally due to the hardness of the soil. You can also notice the poor soil structure and the layering of the soil exemplified by the horizontal cracks. If roots aren’t able to exp
lore as much soil, nutrient uptake and water efficiency are both reduced.
Dr. Stan Barber, Purdue University back in the 1980s showed that two basic facts about fertility was that it wasn’t necessarily the quantity of fertility in your soils, but more importantly the placement of the nutrient relative to the root system. He also found that by increasing the root surface area he was able to increase nutrient uptake. This explains why it “does” matter how large of root system you have.
In the case of calcium, it is only taken up at the root tip, whereas many other nutrients can be absorbed through the root even in older roots across concentration gradients. This is why it is critical to promote as much new root growth as possible. Calcium also stimulates greater root growth. Sustaining root growth later in the season is critical for all nutrients, but particularly those that have a high need later in the season such as calcium, sulfur and boron and are immobile in the plant.
Gypsum is one of the most economical, more soluble products to use to supply calcium to your crop. Gypsum also is one of the best products to use to improve soil structure since the calcium flocculates (groups together) clay particles which may otherwise be dispersed (or separated). This flocculation allows for more pore space to be created which enhances aeration plus more storage for water. With greater pore space you also create an environment that is better for root growth and for microbial activity and earthworms. Both of these produce glomalin and other substances that act as glues to improve soil structure and integrity.
This spring was another challenge for many producers due to the frequent rains and wet fields. Yet again we had customers tell us that they could distinguish the fields where they had applied PRO CAL 40 gypsum. The soils in these fields were less sticky and seemed to b
e more dry allowing them to plant these fields when others were not ready. In some situations, it meant not having to replant while others had to. Using PRO CAL 40 weatherproofs your soils so field work can be more timely. There would have been much less replant this spring if those fields would have had PRO CAL 40 applied to them. It also increases pore space so that water can be stored for use later in the growing season.
When gypsum is used it changes the calcium/magnesium ratio in the soil thus improving the soil condition. Magnesium is what makes soils sticky and difficult to manage because magnesium molecules attract water molecules (as many as 22 water molecules around each molecule of magnesium). At first glance one may think this is good, but this water is held tight and is not available for plant use. It simply makes soils more difficult to manage, become very hard when dry and causes clays to “slick off” creating more sidewall compaction problems. Adding calcium is an inexpensive way to improve drainage.
In addition to this, rain water and snow contain very few electrolytes (distilled) which means that the rainwater picks up electrolytes from the soil. This is good in that it is a driving force for getting minerals into solution, but it is bad because it causes clay soils with less than adequate electrolytes to become dispersed. This causes a surface seal at the soil surface reducing infiltration from subsequent rain events and reducing the soils ability to “breathe”. This dispersion can happen in some soils with as little as ¾ inch of rain. The addition of PRO CAL 40 gypsum provides sufficient electrolytes to prevent this dispersion from happening. This means better air/water exchange by the soil.
Gypsum use also increases root growth by increasing the calcium level in the soil and increasing pore space for roots to grow. The more root growth the greater the nutrient availability. It is critical to have actively growing roots to assure sufficient calcium nutrition at the peak uptake (during the reproductive stages) because calcium is only taken up at the root tips.
This past year White Mold was very prevalent in soybean fields across our area. Many producers are looking for management practices that will decrease the risk of having problems again this coming year. With any disease you must have the disease present, a host plant, and the right environment for the disease to survive. Since White Mold infects the plant at flowering, there is greater likelihood of having a favorable (warm moist) environment especially in heavy soils and narrow rows.
White Mold or Sclerotinia sclerotiorum attacks soybeans through flowers and small pods. It is known to produce oxalic acid which extracts calcium from the pectin that holds together cell walls. As a result, cell walls will collapse. It has been observed that gypsum will decrease the incidence of white mold. It is theorized that the gypsum increases calcium levels in the flowers and stems. This calcium reacts with the oxalic acid neutralizing it thus decreasing the spread of the disease through the plant.
We know that gypsum also helps increase infiltration and decrease standing water. This will decrease humidity somewhat within the growing crop, but more importantly decrease plant stress allowing for more defense of diseases. There has been less White Mold present where PRO CAL 40 has been applied.
There have been nearly 50 different benefits listed for gypsum. It almost gives you the opinion that it does everything, though we know it doesn’t. But when I hear someone say there is no benefit to using gypsum in their soils, I have to question if they understand the value of gypsum. Previous blogs have listed five reasons for farmers to often use gypsum. Following are a few other benefits observed.
Sulfur as a plant food.
Gypsum on a dry basis contains about 23% calcium and 17% sulfur. That means that if you apply one ton of gypsum you will apply about 340# of sulfur per acre. That is enough to meet several years of crops demands. It also makes it one of the least expensive sulfur sources you will find in the market place today. This sulfur is in the sulfate form, the plant available form of sulfur. Since an increasing number of soils are deficient in sulfur applying gypsum can serve to solve this deficiency.
Sulfur effect on other nutrients….manganese, iron and zinc.
Sulfur can enhance the availability of many other nutrients. We have observed this with both iron and manganese. To the left is a picture taken from a field where the corn is showing a manganese deficiency. This was confirmed by a plant tissue test. 
The picture to the right was from the same field where two tons of gypsum had been applied two years previous. As you can see the corn was much greener and without the typical symptoms of manganese deficiency (also supported by plant tissue testing). Research has shown this can happen through sulfur reactions in the soil affecting the manganese availability. The presence of the sulfate ion in higher concentrations serves as a reducing agent for manganese oxide making the manganese more available. The same could also be true of iron. We have also observed that plant tissue tests taken from our fields where we have applied gypsum for several years are much higher than other fields where gypsum has not been applied. Since manganese levels have been decreasing in many soils over the past 15 years this is a significant benefit of gypsum use.
Gypsum has shown to improve manganese availability and microbial activity where glyphosate is used since the calcium can chelate and detoxify the glyphosate.
Sulfur improves immunity.
Sulfur is also vital for healthy soil as it is needed to boost the immune system of the microbes in the soil. By improving the immune system you have healthier microbes and a healthier soil. Then these microbes pass sulfur into the plant for its immunity. There have been numerous studies that have shown that sulfur is very useful in reducing the incidence of a myriad of diseases in crops.
Gypsum improves nitrogen efficiency.
Anyone who farms high magnesium heavy soils understands that nitrogen efficiency is less in these soils. In other words it takes more nitrogen to produce a bushel of grain. These soils have a higher nitrogen requirement to attain equivalent yields than those with less magnesium. Studies done at Purdue have shown that these soils fix more ammonium nitrogen between the clay layers rendering it less available. Their work also shows that where gypsum is applied to these soils, less nitrogen fixation occurs by the clays. In addition, gypsum improves drainage, so soils are less likely to become anaerobic and lose nitrogen to denitrification. All this means less nitrogen being applied and less risk of nitrogen being in streams, etc.
Still more…… Research that was done in the early 1980s at North Dakota State showed that nitrification inhibition occurred with both thiosulfate and sulfate forms of sulfur. In those studies concentrations of 32 ppm in the plow layer was enough to give 80% inhibition of nitrification. With most sulfur sources, unless you apply it with the nitrogen, you will not reach this concentration in the proximity of the nitrogen. However, at the rates of gypsum we often apply we do reach levels that exceed 32 ppm in the plow layer. It could be hypothesized that we could get some nitrification inhibition with the use of gypsum in some soils.
Gypsum improves soils with imbalance from lagoon water.
Where farmers have applied feedlot lagoon water for many years through pivot irrigation, an imbalance of potassium is observed. This is because potassium is very soluble and will be concentrated in the liquid water of the lagoon. Past experience has shown that once %base saturation of potassium exceeds 7% crop production in these fields decrease due to the imbalance. Potassium can also act similarly to sodium at very high levels causing soil structure to deteriorate and soils become hard. Gypsum applications in these soils will improve the soil structure of these soils creating a better balance of cations, reducing the % potassium to manageable levels and improving yields.
Gypsum helps buffer soils from dropping in pH.
When we apply gypsum to soils, we are supplying calcium. Calcium helps buffer soils from acidity. If we can maintain a higher concentration of calcium the soil pH will not drop as quickly. Although gypsum does not contain carbonate, so it doesn’t neutralize hydrogen like limestone does, it does contain calcium which will help maintain a soil pH and keep it from dropping as quickly.
Terrace channels and eroded hillsides are improved.
We have had many users of gypsum start by applying gypsum to their poorest soils first and then continue with their better soils. Soil drainage is improved when applied in terrace channels thus improving production in these soils. Eroded hillsides have also shown to be very responsive to applications of gypsum due to improved drainage, better root development, sulfur nutrition plus other factors already mentioned.
Cover Crops are improved with gypsum applications.
Cover crops are being promoted to improve soil health, but in some soils, due to their impermeability or low levels of calcium in the subsoil, the root growth of the cover crop is reduced limiting their benefits. The picture above shows a field where tillage radishes were grown to loosen up the soil. As you can see the radishes are actually pushing above the ground because they couldn’t penetrate the dense soil. When the radishes were dug, as the next picture shows, the roots only grew about 4 inches before they were severely restricted. 
Gypsum will move through the soil into the deeper layers increasing calcium levels and mellowing the soil so that root systems can penetrate deeper and more extensively.
Tile drainage improved.
When gypsum is applied to soils where drainage tiles have been installed, tile output is increased. There have even been cases where tiles had quit running and once gypsum was applied they started running again. This is a testament to how gypsum will improve infiltration of soils and soil porosity so that water will move through the soil profile. If more water is going into the soil profile then less water will be running off of the field during rainfall events. This means less soil loss and less nutrient loss with the sediment. The soil is a very good filtering system to keep nutrients in the soil profile and not leaving in the drainage water. Some studies have shown that most phosphorus that is found in drainage water from tile lines is through phosphorus movement to tiles through macro-pores such as cracks. Where we have applied gypsum we have seen that we have less large cracks that go so deep. This is beneficial since it relates to better soil structure, but also less risk of nutrients being lost through these cracks to drainage tiles.
Gypsum reduces phosphorus in runoff from fields.
Not only does the use of gypsum reduce the amount of runoff from fields, it also reduces the amount of phosphorus in the runoff water. This is because calcium from gypsum will react with the phosphorus to reduce the amount of dissolved reactive phosphorus in the water. This phosphorus therefore remains in the soil and is still plant available 
phosphorus. Also, gypsum improves soil structure. This means that a clump of soil is less likely to deteriorate with rainwater and so there is less soil sediment in the runoff as is shown in the picture to the right.
No Gypsum Plus Gypsum
The picture above of a slake test using the the same soil, one with gypsum applied to it and the other with no gypsum applied. You can see that where no gypsum had been applied to the soil that the soil clump deteriorated when placed in water and you can also notice how cloudy the water is compared to the soil with the gypsum. You may ask yourself what affect will this have on your soil in your field longterm?
I think you can see that there are many short term benefits to gypsum use, but just as many long term benefits. This is why many long time gypsum users see their yields continue to increase over time. Remember, however, as with any soil amendment or crop input monitor your soils with soil tests so that you realize the most return from your inputs.
Soils contain measurable quantities of aluminum. When the pH of the soil decreases below 5.3, the aluminum is released from within the clay layers and becomes a much more prominent mineral on the soil exchange sites and in soil solutions. Aluminum at high levels (usually > 20 ppm) is toxic to many plants and will affect plant growth. Aluminum causes morphological damage to plant parts. It affects photosynthesis by lowering chlorophyll content and reducing electron flow. Reduced respiratory activity might be due to reduced metabolic energy requirement. Protein synthesis is decreased. Aluminum interferes with the uptake, transport and use of several essential elements, including Cu, Zn, Ca, Mg, Mn, K, P and Fe.
In corn, when aluminum levels increase above 20 ppm you begin to see root growth cease. The roots will be clubbed off and stunted as seen in the picture to the right. It will resemble other symptoms such as some nematodes or herbicide damage.
Below are some results from samples I took from a Nebraska field where aluminum toxicity was evident. Location 1 showed more stunting of the corn plants and more root symptoms than Location 2. Where pH was lower and aluminum levels were higher plant symptoms were more severe as would be expected.
| Location 1 | Location 2 | |||||||
| Soil depth | Soil pH | Aluminum, PPM | Soil depth | Soil pH | Aluminum, PPM | |||
| 0-3″ | 4.5 | 17 | 0-3″ | 5.9 | 4 | |||
| 3-8″ | 4.3 | 74 | 3-8″ | 5.2 | 32 | |||
| 8-18″ | 4.5 | 84 | 8-18″ | 5.1 | 52 | |||
If the pH is acidic in the top 3-4 inches it is easy to solve with an application of lime, however, when acidic soils are found below 6 inches it is more difficult to manage. Lime moves very little in the soil. One approach is to apply a heavy rate of lime (4 ton) and plow it under deep. This is often not preferred since erosion of these soils will be increased and lime still won’t move much. Frequently the soils with this condition are sandy soils.
Another way to manage these soils with acid subsoils is to apply gypsum and let it move through the soil profile. Gypsum is much more mobile than agricultural lime. The gypsum will dissolve and dissociate as it moves deeper in the profile. The sulfate ions from gypsum react with the aluminum fixing it from being plant available. The calcium also reacts to form calcium hydroxide which will react further to increase the pH. The calcium from the gypsum is available for plant uptake, since these low pH soils are deficient in calcium also. Aluminum in sandier soils also tends to cause the sand particles to cement together and form a dense layer. It is usually beneficial to also use subsoil tillage to break up this layer.
The only way to know if you have these soil conditions is to dig some plants and look at the roots, but also take a soil sample at different depths. For example, sample from 0-6 inch and then take another sample from 6-12 inches and see what the pH of each of these depths are.
If you need help in what rates of lime and/or gypsum to apply in these conditions, give us a call and we can assist you.
In the past and in many “Soils” books magnesium and calcium were put in the same category concerning effects on soil physical properties. The reasoning was that they both had two positive charges. In recent years, these ideas have changed. Magnesium has a greater attraction for water and thus has a larger hydrated radius than calcium. This causes soil particles to remain farther apart and more dispersed. For this reason soils with higher magnesium contents have less water stable aggregates and less pore integrity. These soils usually are stickier and remain wetter and saturated longer. If saturated, root growth is diminished significantly.
What does this mean for you, the farmer? These soils with high magnesium remain wetter and colder in the spring and timing of field operations are more difficult. Sidewall compaction is more common in these soils since they tend to “slick off” with any sheering. The picture above shows a soil with a magnesium content greater than 25% and a CEC greater than 30. Notice the poor soil structure and how compact the soil is (less soil porosity). By increasing the calcium concentration relative to the magnesium, you can change the properties of these soils greatly. If the pH is low, you can increase the calcium concentration relative to magnesium by adding high calcium lime. If the pH is 6.0 or above an effective means of increasing calcium relative to magnesium is adding gypsum. Gypsum is more water soluble than lime at a pH above 6.0 and will give you a faster response. With gypsum the calcium will replace the magnesium on the soil particle and the magnesium will react with the sulfate to form Epsom salt and will be leached deeper into the profile or removed with drainage water. This means that you can be more timely with your field operations.
This year we had several farmers observe that they were able to plant the fields where they had a
pplied the gypsum, but were not able to in the fields where no gypsum was applied since those fields were too wet. The field to the left shows the difference where gypsum was applied vs. no gypsum on the amount of water standing after a rain.
Nitrogen efficiency is decreased in soils with higher magnesium since the soils often times lack oxygen and soil nitrogen is denitrified or lost. Also since microbial activity isn’t as great when oxygen is depleted there isn’t as much organic nitrogen released to the growing crop. Refer back to the blog on calcium and having a good balance between nutrients to understand why an imbalance of calcium and magnesium is detrimental.
In fields where gypsum has been applied tillage operations require less horsepower since they are not a sticky and do not pull as hard. When installing drainage tiles in fields where gypsum has been applied, a tile plow will pull much easier.
In summary, gypsum is a good source of water soluble calcium as was highlighted in a previous blog. This calcium will displace magnesium on the soil particle increasing calcium base saturation. This will improve soil physical properties. As the magnesium is displaced, it will react with the sulfate ion and will leach deeper into the profile or be removed with drainage water.
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