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Research Update - Liming Impacts on Soils in Western ND

By: Chris Augustin, Director/Soil Scientist Dickinson Research Extension Center
Posted: Apr 27 2023

Research funding remains a priority for the NDWC with nearly 40% of the annual budget dedicated to research and customer service related work.  The article below summarizes work that was partially funded by the NDWC. This research project evaluated the impacts of surface lime applications on soil in order to develop lime recommendations to remediate soil acidity.

Soils become acidic from the mineralization of ammonium-based fertilizers. No-till soils are particularly susceptible to acidification from the lack of mixing subsurface alkaline products and the tendency to apply ammonium-based fertilizers at or near the soil surface. As a result, the zone of acidification is at the depth of fertilizer placement. Soil acidity is a soil health issue that reduces fertilizer efficiency through nutrient tie-up and aluminum toxicity. Aluminum toxicity further hinders plant growth and nutrient uptake by stunting and malforming root development. 

Acid acres are corrected by applying a lime or another soil amendment that neutralizes the hydrogen ion. Lime is comprised of calcium-carbonate. Calcium does not neutralize soil acidity as calcium and hydrogen are positively charged soil cations and repel from each other. However, the carbonate in lime is negatively charged and produces water and carbon-dioxide when neutralizing hydrogen ions that cause soil acidity. 

Having said that, the first step in managing soil acidity is to soil test. Whole field or composite soil testing will not truly show the pH status of your field since there is a dilution effect from the mixing of different soil types. Zone sampling a field will better pinpoint the acid acres in a given field. 

Recent research compared the soil pH of various sampling depths (figure 1). The lowest pH was observed at the 0-3 inch depth and was similar to the 0-2 inch depth. Similar soil pH’s were observed at the 0-6, 0-2, and 2-4 inch depths. The 4-6 and 3-6 inch soil pH were the greatest.  All collaborating producers were long-term no-tillers. The majority of producers either applied nitrogen at the surface or a few inches into the soil. This data suggests that the 0-3 inch soil test will better identify soil acidity issues and better account for the environment of seedlings. The 0-6 inch soil test depth results are diluted due to deeper collected alkaline material.   

The Dickinson Research Extension Center team has been working hard to develop lime recommendations for North Dakota soils with North Dakota data. So far we have assessed lime impacts of eleven of twenty four sites.  While the sites are concentrated in the southwest quarter of the state, there are a few sites near the Minot area and further east.  We soil sample in the spring and apply lime as sugarbeet waste lime immediately after soil collection. In the fall we return and soil sample to determine the change of soil pH over the course of the growing season. All locations are no-till and the lime was not incorporated.  Keep in mind that in order to remediate acid soils, you will likely need tons of lime. Table 1 is a summary of the 11 evaluated acid sites. 

To use Table 1 you need to know your soil Buffer pH. This measures the soil’s ability to resist a pH change. The lower the buffer pH, the more lime is needed to increase pH. Once you have your buffer pH, then you need to determine your desired pH. From there, the intersection of the buffer pH and desired pH is your lime recommendation. For instance, 5.5 tons of calcium carbonate per acre is recommended if your soil buffer pH is 6.7 and desired pH is 6.0. Some recommendations in table 1 are red. That indicates the data doesn’t quite look right. This table will be adjusted once all the data has been analyzed.

Make sure to test the calcium carbonate equivalent (CCE) in whatever liming amendment you may use. The sugarbeet waste lime we have used has ranged from 55 to 85% CCE. Calcium carbonate equivalent should be tested regularly to ensure you are maximizing the cost of your lime inputs.  

When it comes to managing acid soils remember to: 

1. Precision soil sample to pinpoint acid acres. 
2. Soil sample at the 0-3 inch depth. 
3. Apply an acid neutralizing amendment. The carbonate portion of calcium-carbonate neutralizes acid causing hydrogen. 
4. Make sure you know the calcium carbonate equivalence of the liming amendment you are using.

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