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Why Gypsum Works in Your Soil: Part 3 Gypsum Improves Alkali soils

October 15, 2015

Gypsum has been used for centuries to reclaim sodium affected soils (alkali soils). It is effective since it has good solubility regardless of soil pH. In fact, its solubility is enhanced in sodic soils. Some data would suggest that the solubility of gypsum in alkali soils is four times greater. Once the gypsum dissociates into calcium and sulfur the calcium has the greatest attraction for the soil particle displacing sodium. The calcium will help flocculate (aggregate) the soil whereas the sodium on the soil causes dispersion. This means that calcium from the gypsum will improve soil structure and improve plant growth.

It is important that you apply the proper rate of gypsum based upon soil tests to see the best responses. We have found that higher rates of gypsum need to be applied if you have sodium present plus high levels of magnesium, since both minerals will cause dispersion of the clay particles. If you have this condition and need assistance in what rate to apply please give us a call.

How fast your soil structure is restored depends upon how high your levels of sodium in the soil are. Typically, you will see a quick change in soils and less water ponding, however, as plants begin to grow in these soils you will see biological activity return and gradually improve with each growing season. Remember, your soil did not get to this point in one growing season. You can’t expect the soil to be reclaimed in one growing season. However, the picture to the right was taken from a field where PRO CAL 40 gypsum was applied in the spring prior to planting the soybeans. You can see that there was a marked improvement in the soybeans where treated.

If subsurface drainage is a problem installing drainage tile will help flush the sodium from the soil profile. Gypsum applied to the surface will reduce the surface sealing in these soils and improve the effectiveness of the drainage tile.

Once calcium levels are restored to an optimum range of 75% base saturation, the soil structure will improve, the root development will be larger and yields will be closer to the field average.

Why Gypsum Works in Your Soil: Part 2 Good Source of Calcium in all Soils

October 5, 2015

Gypsum contains about 22% calcium and since soil pH has little effect on its solubility, it is a good source of calcium in high pH soils. Calcium in high pH soils often is fixed as calcium carbonate. Managing alkaline soil pH is best done by maintaining high levels of free calcium in the soil. This is why gypsum is added to soils with high soil pH (>8.0). Gypsum is an excellent and inexpensive source of soluble calcium.

Calcium is often overlooked as a crop nutrient. Most soil fertility specialists assume that so long as your soil pH is sufficient that you will have adequate calcium nutrition. This is only partly correct.

We should first consider the importance that calcium plays in the plant. Calcium is sometimes called “the trucker of all nutrients”. This is because calcium improves the absorption of all nutrients and helps in their translocation within the plant. Calcium helps neutralize organic acids in plants that form during cell metabolism, therefore helping maintain proper pH. Calcium activates several enzyme systems that serve as plant growth regulators. Calcium helps convert nitrate-nitrogen into ammonium forms of nitrogen needed for protein formation. Calcium is critical for normal cell division and for strong cell walls. Also very important is that calcium improves disease resistance in plants. Lastly calcium improves water use efficiency by plants.

Calcium Improves Water Efficiency

Nutrients can play a key role in improving plant water efficiency. Calcium is most important for water efficiency because:

Calcium and calmodulin (calcium modulated protein) act as a messenger molecule to jump start plant protection devices.
Calcium helps stabilize plasma membranes and decreases hydrogen peroxide concentrations which increase with drought stress. This maximizes cell water content.
Calcium is vitally important for root hair growth increasing root surface area significantly increasing water uptake.
Calcium works with abscisic acid (formed especially when under drought stress) to increase water conductivity within the plant.
Calcium is involved with the closing and opening of the stomata decreasing transpiration losses.
Calcium improves cell wall thickness and reduces cuticle breaks where water can be lost from the leaf.

In the soil, calcium works with microbial populations to improve decomposition of organic matter and crop residue to convert to plant available nutrients. It also enhances nitrogen-fixing bacteria in the soil so that more nodules are formed on legume roots increasing the amount of nitrogen produced. Obviously, calcium plays a key role in plants and soil.

Factors that can affect calcium availability from the soil is the balance with other nutrients. If calcium is low because you have an imbalance with magnesium, potassium, sodium, aluminum or hydrogen, your plants may be stressed. If pH is low, you may encounter an imbalance with hydrogen and aluminum (particularly pH< 5.3). If your soils have been heavily manured or received high amounts of lagoon water you may have an imbalance with potassium and possibly magnesium. In some soils you may have high magnesium levels due to the soil’s parent material (or soil erosion) that can cause an imbalance with calcium. These soils will be stickier and less friable decreasing root development and nutrient uptake. They also have slower water infiltration, which will also reduce water efficiency.

Another factor that can affect calcium availability is high levels of carbonates and bicarbonates in the soil. This will be related to high sodium levels and/or high pH levels in the soil. Irrigation water can also contain high levels of carbonates and bicarbonates. Carbonates and bicarbonates will react with calcium making this calcium less available for plant uptake. This calcium will probably appear on the soil test as exchangeable calcium, but in reality is not plant available. This is why some high pH soils may actually be low in calcium availability. Acid reactions in the soil that acidify this calcium carbonate will make the calcium available.

Most common sources of calcium for agricultural crops include calcium carbonate (limestone) and calcium sulfate (gypsum). Both are good sources of calcium as long as they have small particle size and applied in the correct soil conditions. Limestone is most effective as a calcium source in low pH soils where it will be reactive. It is not a good calcium source in high pH soils since it won’t be soluble. Gypsum is a soluble form of calcium at all soil pH levels.

Why Gypsum Works in Your Soil: Part 1 Reduces Surface Sealing

September 30, 2015

There are many reasons why we see responses from gypsum in agricultural soils. This blog is the first of six discussing the benefits of gypsum.

Gypsum gives responses in most soils by supplying a good source of electrolytes which rain water can react with. Without electrolytes present, rain water will cause greater soil dispersion and surface sealing. The benefit of having gypsum soluble, but not too soluble, is that it will not leach quickly through the soil profile and will stay near the soil surface where it can reduce surface sealing.

With heavy rains in many areas this year surface sealing could be a greater concern since the electrolytes in the soil will be depeted. Gypsum applications will alleviate these soil problems.

The solubility of gypsum is about 2.05 g/L in water (77 degrees Fahrenheit). This is about 200 times the solubility of most liming materials. Fineness of grind or particle size will also greatly affect dissolution rates and solubility of both lime and gypsum. In soil, it has been determined that gypsum passing a 100 mesh screen will solubilize at a rate of about 35# per one inch of rainfall.

In the picture to the left you can see the white gypsum that is still visible in the soil from the previous year’s application. Also notice the granular soil structure. Earthworms were easily observed in this soil and their “huts” of leaves and crop residue were prevalent. Typically, we have observed that a ton of PRO CAL 40 applied per acre will last about three years given the rainfall we receive during the growing season. This gypsum near the surface continuing to solubilize reduces surface crusting over those three to four years. When you spread the cost of a gypsum application over four years, the cost per acre is less than $10 in most of our marketing area. That is very economical considering that many customers have shown 10 bushel or more responses in corn and five plus bushels in soybeans all while improving their soil both short term and long term. “My soil just keeps improving each year after an application of PRO CAL 40”, said one of our customers recently. We have experienced the same on our farm.

Don’t forget the Micro-organisms!

May 26, 2015

At first glance, soil appears to be quite lifeless, however, when you look at it under a microscope you find that it is anything but. In a single teaspoon of soil it is estimated that there are billions of microbes. Microbe populations include fungi, bacteria, protozoa, actinomycetes and nematodes. The area around the plant roots become a hotbed of microbial activity and adding carbon to the soil surrounding roots greatly increases the number of microorganisms. Much of this added carbon comes from root exudates. These are a gel-like substance that is produced by plant roots. In some plants as much as 1/3 to ½ of the carbon produced during photosynthesis is exuded through the roots.

Many factors can affect this microbial activity including moisture, pH, soil texture and soil structure. Improved soil structure increases root growth and results in greater extraction of water and nutrients. Greater soil aggregation results in better porosity which means potentially more water holding capacity or greater soil aeration. Gypsum improves soil structure and soil aggregation, thus can greatly enhance microbial activity. Some studies have shown that by improving soil structure, less soluble phosphorus is required for plant growth. This could be related to improved root growth plus increased microbial activity around the roots increasing nutrient uptake.

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March 14, 2015

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