Flanary, W.E., Agronomy Specialist, University of Missouri Extension
Chapple, R.W., Retired Ag Engineer, University of Missouri Extension
Crawford, J.J.W., Natural Resource Engineer, Superintendent Graves Chapple Research Farm, University of Missouri Extension

ABSTRACT

Gypsum is promoted to increase water infiltration and increase crop yields on poorly drained soils in northwest Missouri. The objective of this experiment was to determine if the use of gypsum would increase water infiltration and crop yields.  Gypsum application rates of 300, 500 and 1,000 pounds were applied to a Salix silty clay loam located at the Graves Chapple Research Farm located at Corning, MO.  Water infiltration rates were measured 12 months after application. Crop yields were measured from 2004 to 2007. The application of gypsum did not increase water infiltration rates or crop yields. The research results were discussed during field days, annual reports and update meetings reaching more than 850 growers.  The use of gypsum in northwest Missouri does not lead to increased water infiltration and improved crop yields.

Introduction

Gypsum is used to correct sodic soils in Oklahoma and Kansas (Lamond, 1992; Zing, 2009). Gypsum is marketed in northwest Missouri to increase water infiltration rates without any regard of soil sodium levels. 

Soil testing is the first step in identifying if an application of gypsum would improve water infiltration.  The soil test results are used to indicate if the soil is saline, sodic, saline-sodic or not affected by any salts.  Saline soils can be reclaimed by applying a quality water to leach the excessive salts from the soil. Sodic soils must have the excessive sodium replaced by another cation and then leached.  Sodic soils are treated with gypsum to provide a source of calcium to replaces the sodium.  Once gypsum is applied, then a quality water is added to move the sodium beyond the root zone.  Rates of gypsum are applied at rates of tons per acre rather than pounds per acre to improve sodic soils.

When sodium content is significant, the application of gypsum to the soil surface can increase water infiltration rates.  Keren (1983) and Morin (1996) found that application rates of 2 tons per acre increased water infiltration rates.  Research by Ben-Hur (1992) found if soils were not dispersed, then gypsum did not increase water infiltration rates.

Gypsum can also be used as a source of sulfur.  Soils that may be responsive to sulfur may respond to the sulfur contained in gypsum.

The objective of this study was to determine if the application of gypsum would increase water infiltration rates and crop yields. The results of this study would be provided to area growers so they could make informed decisions about the use of gypsum.

Materials and Methods

The study was conducted from 2004 to 2007 on a Salix silty clay loam soil located at the University of Missouri Graves Chapple Research Farm , Corning, Missouri.  The Salix silty clay loam soil is a poorly drained soil. Soil test data indicate the level of salts present in the soil are not great enough to impact crop growth.

Treatment application rates of 0, 300, 500, 1,000 pounds of gypsum were topdressed and left unincorporated.  The plots were no-till planted across all years and the plot area was in a corn and soybean cropping rotation. Plots measured 10 feet wide by 30 feet in length. The experiment was conducted in a randomized complete block design with five replications 

Infiltration rates were measured 12 months after the gypsum application using metal barrels driven into the soil.  Five gallons of water were poured into each barrel and the time for the water to disappear from the inside of the barrel was measured.  Five gallons of water poured into a barrel would approximate a 3-inch rain. One barrel was placed in each of the five replications.

The plots were maintained for four years to determine if any long-term benefit from the gypsum application could be gained.  Crop yields were measured each year to determine if there were treatments effects.

Infiltration and yield data was analyzed by Proc ANOVA using AGSTATS (Oregon State University, 2009). 

Results and Discussion

The application of different rates of gypsum did not increase water infiltration rates (Table 1) measured 12 months after application. 

 

Table 1. The effect of gypsum treatments on water infiltration 12 months after application.

Gypsum Treatments(lb/ac)	Time required for 3-inches of water to disappear from inside the barrel (minutes)
Check	17.25
300	12
500	14.75
1,000	22.5

LSD (0.05) = NS

 

No significant differences in corn and soybean yields were measured in individual years from 2004 to 2007 (Table 2).

 

Table 2. Effect of gypsum applications on crop yields.

	2004	2005	2006	2007
Gypsum application rates	Corn (bu/a)	Soybean (bu/a)	Corn (bu/a)	Soybean (bu/a)
0	162	57	171	57
300	168	59	165	58
500	164	53	173	57
1,000	164	56	170	56

LSD (0.05) = NS

 

The Salix silty clay soil does not have the characteristics that would benefit from the application of gypsum for water infiltration. If the site had large amounts of sodium, then the gypsum would allow the leaching of sodium from the soil particles. Also, if the site was sulfur deficient, then crops could use gypsum as a source of sulfur.

Education efforts of this study included the Graves Chapple Research field days, publication and distribution of annual reports, providing results duirng the Extension Ag Update meetings held in each of the fifteen counties in northwest Missouri.

Summary

The use of gypsum did not increase water infiltration or crop yields.  Soil test data indicated salt levels were low and would not impact crop yields. The University of Missouri Extension provided applied research and education to more than 850 growers.

References

Lamond, R.E., Whitney, D. A. 1992.  Managment of Saline and Sodic Soils , MF-1022, Kansas State University Agricultural Experiment Station and Cooperative Extension Service.

Keren, R., Shainberg, I., Frenkel, H. and Kalo, Y., 1983.  The effect of exchangeable sodium and gypsum on surface runoff from loess soil. Soil Science Society of America Journal 47:1001-1004.

Morin, J., Winkel, J. V., 1996. The effect of raindrop impact and sheet erosion on infiltration rate and crust formation. Soil Science Society of America Journal 60:1223-1227.

Zhang, H. 2009. Reclaiming Slick-Spots and Salty Soils, PSS-2226, Oklahoma Cooperative Extension Service.

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