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Response of Soils and Crops to Gypsum Application in Ohio

ANR-0153
Agriculture and Natural Resources
Date: 
07/26/2024
Manbir Rakkar, Soil Fertility Specialist/Assistant Professor; Food, Agricultural, and Environmental Sciences; The Ohio State University
Greg LaBarge, Field Specialist/Professor; Food, Agricultural, and Environmental Sciences; Ohio State University Extension

Gypsum is a source of calcium (Ca) and sulfur (S) for crop nutrition. Calcium is also used for soil balancing of base cations and as a soil amendment to improve soil tilth and health (Chen and Dick, 2011). However, the application rates and frequencies sufficient to obtain soil and crop benefits from gypsum are often unknown. This article discusses the response of soils and crops in Ohio based on recent published studies.

Two large white piles of gypsum on grass in front of tilled cropland.Gypsum as a source of sulfur (S) for crop nutrition: Sulfur fertilizer recommendations are becoming more common due to increased crop removal as a result of increased yields and reduced atmospheric S inputs. But does the S in gypsum application result in yield increases in Ohio? The results are mixed regarding the crop responses to gypsum inputs.

Gypsum contains S in sulphate form, which is readily available to crops. Fleuridor et al. (2020) reported no improvements in crop yields from gypsum additions in the majority of organic system cases. The study was conducted at 14 locations with a total of 25 experiment sites over two years (2017–2018). The response of grain corn, silage corn, forage, and oats were tested using a 1 ton/ac gypsum application. Gypsum was applied within one week of crop emergence in row crop fields and in early spring for forages. The gypsum application added about 350 lb of S per acre. The farms also received organic fertilizers, such as manure, chicken litter, and fish products, to meet other crop nutrient demands. Out of the 25 experiments, the yield for second-cut forage increased in one of the experiments (Table 1). The authors mentioned that a yield increase from additional S is less likely where manure is commonly applied.

Another study published by Fleuridor et al. (2023) also reported an infrequent response to S application. The study summarized 96 Ohio S response trials conducted between 2013–2021, including 62 trials where gypsum was the S source. The rate of gypsum applied among experiments in the study ranged from 4.5 to 720 lb of S per acre. Across 62 trials, a yield increase was observed in four trials—two in corn, two in soybean, and none in wheat—with one corn site showing a decline in yield (Table 1). The positive response sites received S at an application rate of 20–180 lb of S per acre.

Chaganti et al. (2019) evaluated the response of corn based on the rate and frequency of gypsum application in a four-year experiment at two sites. The application rate of gypsum included 0, 0.5, and 1 ton per acre. Application frequencies were annual (0.5 ton/ac), biannual (1 ton/ac), and every four years (2 ton/ac). The response of gypsum application was tested on continuous corn over four years. The experiment also consisted of different nitrogen (N) rates (0, 75, 150, and 225 lb of N per acre) to evaluate the interaction of gypsum and N. The study observed a yield increase at one of the two sites in one of the four years, but there was no interaction between N and gypsum application (Table 1). Gypsum applied on a biannual or annual basis was, however, found to be more beneficial than applying gypsum once at a 2 ton per acre rate. The one-time application of 2 tons per acre of gypsum lowered corn yield in one of the four years at both locations.

A general finding across all studies summarized here is that biomass S in leaf and grain increased due to gypsum application. Thus, gypsum application may improve the feed value of forage and grain.

Table 1 (click to download PDF). Summary of crop yield response to gypsum application in Ohio from 2013 to 2021.
Table showing how crop yields change due to gypsum application from 2013 to 2021 in Ohio.

As less tillage is becoming more prevalent across Ohio cropland, organic matter is likely to build up slowly over the time. Sulfur is a component of soil organic matter, and as this organic matter is mineralized, sulfate is released, acting as a slow-release fertilizer that feeds sulfur to the crop plants. Conversely, tillage speeds up the mineralization process and the sulfate released is prone to leach before it can be utilized by the crop. Thus, as more conservation tillage is being adopted in Ohio, there may be less need for sulfur fertilizer inputs due to improved organic matter levels.

Gypsum as a source of calcium (Ca) for soil balancing: The quantity of one nutrient in soil can have a synergistic or antagonistic effect on plant uptake of other nutrients. For example, calcium (Ca) and magnesium (Mg) ions have been reported to have an antagonistic effect. Studies have also shown that the presence of excess potassium (K) can negatively affect the uptake of calcium and magnesium ions by plants. To attain an ideal ratio of base cations, a concept of soil balancing or basic cation saturation ratio came into existence in late 1800s. Work done in New Jersey and Missouri in the 1930s and 1940s proposed an ideal ratio of exchangeable Ca, Mg, and K as 13:2:1 to optimize plant growth. This ratio has since been modified to a wider range of percentages on the soil exchange sites: 60–75% Ca, 10–20% Mg, and 2–5% of K.

Gypsum is often used as a source of calcium for soil balancing of the cations. But does soil balancing positively affect crop yields? Chagnati and Culman (2017) reviewed studies from 1933 to 2008 and found no significant benefits on crop yield in the majority of the cases. Most of the crops were able to grow well in a wide range of Ca:Mg ratios as long as there was no nutrient deficiency. The authors concluded that the practice of maintaining an ideal cation ratio to increase crop yields lacks substantial scientific evidence.

Gypsum as an amendment to improve soil tilth, soil health, and water quality: The use of gypsum to improve sodic soils is well documented. Sodic soils have excess sodium on exchange sites that causes soil dispersion and water infiltration issues. When gypsum is applied to sodic soils, the calcium ions of gypsum replace sodium on exchange sites, which improves soil aggregation, indicating that gypsum application is beneficial in sodic soils. Sodic soils are rarely found in Ohio.

But does gypsum benefit non-sodic soils? Long-term studies are needed in Ohio to monitor the effects of gypsum on soil health. In a two-year study, gypsum did not show changes in penetration resistance (a compaction indicator) and unsaturated hydraulic conductivity (a parameter of water movement in soil profile) (Fleuridor et al., 2021). The study also observed a decline in soil protein but no effect on permanganate oxidizable carbon and mineralizable carbon due to gypsum. However, Mg levels decreased due to their replacement by Ca ions from exchange sites. The presence of Ca ions on exchange sites instead of Mg is often favorable as it causes soil flocculation and improvement in the soil’s physical properties.

One potential benefit of gypsum application is improved water quality. King et al. (2016) observed a 41% reduction in dissolved reactive phosphorus (P) and a 40% reduction in total P loads in surface runoff after two gypsum applications of 1 ton/ac. The study also showed a 25% and a 15% reduction in dissolved reactive P and total P loads in tile discharge, respectively. Gypsum application increases the amount of calcium in soil and water, which could reduce the solubility of soil P and decrease P loading in runoff.

Summary

  • Gypsum is a good source of calcium and sulfur.
  • Positive yield responses to gypsum application are rare in Ohio.
  • An increase in sulfur concentration in soil and crop biomass is frequently observed with gypsum.
  • Limited research is available to support soil balancing benefits through gypsum application.
  • Short-term benefits of gypsum on soil health were not prevalent, but long-term benefits should be evaluated.
  • Gypsum application has benefits for improving water quality by decreasing the P loads in runoff.

References

Chaganti, V. N., Culman, S. W., Dick, W. A. & Kost, D. (2019). Effects of gypsum application rate and frequency on corn response to nitrogen. Agronomy Journal, 111(3): 1109–1117.
acsess.onlinelibrary.wiley.com/doi/10.2134/agronj2018.10.0683

Chaganti, V. N. & Culman, S. W. (2017). Historical perspective of soil balancing theory and identifying knowledge gaps: A review. Crop, Forage & Turfgrass Management, 3(1): 1–7.
acsess.onlinelibrary.wiley.com/doi/10.2134/cftm2016.10.0072

Chen, L. & Dick, W. A. (2011). Gypsum as an agricultural amendment: General use guidelines. Ohio State University Extension.
fabe.osu.edu/sites/fabe/files/imce/files/Soybean/Gypsum%20Bulletin.pdf

Fleuridor, L., Fulford, A., Lindsey, L. E., Lentz, E., Watters, H., Dorrance, A., Minyo, R., Richer, E., Chaganti, V., Kumaran, S., & Culman, S. W. (2023). Ohio grain crop response to sulfur fertilization. Agronomy Journal, 115(4), 2007–2016.
acsess.onlinelibrary.wiley.com/doi/10.1002/agj2.21328

Fleuridor, L., Herms, C., Culman, S., Dick, W. A., Paul, P. A., & Doohan, D. (2021). Short-term responses of soils and crops to gypsum application on organic farms. Agronomy Journal, 113(5), 4220–4230.
acsess.onlinelibrary.wiley.com/doi/10.1002/agj2.20669

King, K. W., Williams, M. R., Dick, W. A. & LaBarge, G. A. (2016), Decreasing phosphorus loss in tile-drained landscapes using flue gas desulfurization gypsum. Journal of Environmental Quality, 45(5): 1722–1730.
doi.org/10.2134/jeq2016.04.013

Originally posted Jul 26, 2024.
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