Reflections and soil amendments

In the next couple months, harvest season will be wrapping up and the actual field production will be determined. This is the moment of truth for farmers and a reflection of the year. 

It is also a critical time to assess and reflect on field conditions and start making plans to address those conditions for next year. Field conditions vary greatly between fields and across the state, and many factors contribute to poor production. Each individual field should be assessed for reasons leading to poor production.

Not surprisingly, Wyoming’s soils can be a major contributor to poor production. To improve the soil’s properties (chemical, physical and biological) and processes, a soil amendment may be necessary. Common granular soil amendments utilized in agriculture are lime, manure, biochar and gypsum. Liquid soil amendments are also available and can be broadcast on the field or infused in fertilizers.

Soil amendments benefit production by various means, including raising pH, adding nutrients, increasing soil organic matter and improving soil water storage. The type of soil problem dictates which amendments should be utilized.

Soil amendments

As some probably know, certain soil amendments, such as lime, are not beneficial for Wyoming soils. Lime is used to increase soil pH, which is not what Wyoming soils typically need, and add calcium to the soil. Liming is typically performed on acidic soils and can take three to four years to see yields increase. 

Manure has been utilized for many years and remains a viable soil amendment. Manure can increase soil nutrients, water retention and soil organic carbon, as well as reduce compaction. Be aware, manure must be used appropriately and targeted for specific field conditions. 

Interestingly, overapplication of manure can cause detrimental effects, such as water repellency and ponding. A study by the University of Nebraska indicates applying manure to semiarid soil for 71 years increased water retention and decreased soil compatibility.

Unlike manure, biochar is a newcomer to soil amendments and is not fully researched in agriculture systems. This carbon-rich organic material has the potential to benefit soil properties. 

Studies by the University of Nebraska have shown biochar can retain nutrients and reduce volatilization of fertilizers. It is ideal for lighter soils or soils with a high sand component, which are low in cation exchange capacity, poor water holding capacity and weak aggregate stability or soils low in organic matter. Note, the use of biochar may be cost prohibitive.

Gypsum applications

Like lime and manure, gypsum can be both a fertilizer and a soil amendment. However, unlike lime, gypsum does not raise soil pH and has a higher solubility, which makes it ideal for alkaline soil types. Gypsum can be applied as a fertilizer to provide crop-available calcium and sulfur; soils deficient in these elements benefit from gypsum applications. 

Before applying gypsum, make sure to test soils to see if they are deficient in calcium. Wyoming calcareous soils are not deficient and will test high for free lime on a soil test. The sulfur can be beneficial as a fertilizer if there is a deficiency.

When used as a soil amendment, gypsum is ideal for addressing soil structure issues, including poor soil aggregation, slow water percolation and soil crusting. Gypsum is known as a strong flocculator, which means it forms stable soil aggregates, or binding together of soil particles, encouraging water infiltration and drainage which reduces soil crusting. 

Gypsum can positively impact dispersed soils, or soil particles not bonded together, such as sodic soils (high in sodium and low in salts) and sodic-saline soils (high in both sodium and salt). Applying gypsum to these soils adds large amounts of calcium, which displaces the sodium ions from clay particles. This encourages soil aggregation and allows the sodium to be flushed with salts from the soil; however, it is only effective if there is proper drainage in the subsoil. 

Gypsum is not beneficial for all soil conditions; in particular, look out for saline soils (low in sodium and high in salts). Applying gypsum to these soil conditions will compound the salt problem. 

No matter what soil amendment is being considered, doing homework ahead of time is essential. Learn as much about the product, test soils to understand the exact conditions needing to be addressed and work with an Extension agent or crop consultant to ensure the best chance of success. 

Remember, soil amendments only address specific conditions in the soil and are only beneficial when those conditions are present.

Jeremiah Vardiman is a University of Wyoming Extension educator. He can be reached at jvardima@uwyo.edu.