Clevenger, W. B., Assistant Professor and Extension Educator, Ohio State University Extension
Islam, R.K., Research Scientist, Ohio State University

ABSTRACT

This study evaluated the effect of soil applied gypsum on crop yields (soybean, corn and wheat) and soil quality on poorly drained, clay soils. Conducted in northwestern Ohio, gypsum treatments included 1.0 and 2.0 tons per acre compared to a nontreated control.  The effect of gypsum on soil quality was determined by soil samples collected and analyzed in a laboratory for biological, physical and chemical properties.  Gypsum had a significant effect on select soil quality characteristics in this study.  During the years 2004-2009, gypsum did not have a significant effect on crop yields compared to the nontreated control plots.

Introduction

The use of gypsum on clay soils has become increasingly popular in northwestern Ohio.  Gypsum is hydrated calcium sulfate (CaSO4•2H2O), and is often marketed as a soil conditioner for improving soil tilth (Dontsova et al 2005). Benefits that may result from gypsum applications include a reduction in soil crusting at the surface, increased aggregation of clay soil particles, and increased water infiltration (Chen 2011).  A soil that has a favorable and stable soil structure also promotes rainfall infiltration and water storage for plants to use later (Magdoff & Van Es 2009).  Soil quality integrates the physical, chemical and biological components of soil and their interactions (USDA 1999).  Gypsum is also about 200 times more soluble than agricultural lime, or calcium carbonate, allowing it to move readily down the soil profile (Chen & Dick 2011).  Use of gypsum as a sulfur fertilizer to enhance crop production in sulfur deficient soils has been proved from many crops such as corn, soybeans, canola, and alfalfa (Chen & Dick 2011).

Materials and Methods

This research was conducted at the Defiance Agricultural Research Association (DARA) site in Defiance County, Ohio during crop years 2004-2009. The soils are a mixture of Roselms silty clay (very fine, illitic, mesic, Aeric, Eqiaquepts) and Paulding clay (very fine, illitic, nonacid, mesic, Typic Epiaquepts). The soils are deep, fine-textured and poorly drained which developed on lake plains from calcareous lacustrine sediments. On average, the soils contain 5 - 11% sand, 34 - 50% silt, 40 - 60% clay, and 17 - 50 meq 100 g-1 cation exchange capacity (USDA 2014). 

Treatment rates of gypsum were 0.0 ton (control), 1.0 ton and 2.0 ton per acre applied broadcast to the soil surface without incorporation.  Treatments were made March 2004 to plots that measured 30 feet wide by 530 feet long with each treatment replicated in a randomized complete block design.  Corn and soybeans were grown in rotation each year during 2004-2007.  All plots were planted to soybean and wheat during 2008 and 2009, respectively.  All plots received the same agronomic treatments such as seed, chemical and fertilizer annually for their respective crop.  Crop yields were measured for each plot annually to determine a treatment response. 

Soil quality was measured in November 2004 and November 2005 using soil sample analysis.  Composite soil samples from each plot were collected at 0-6 inch soil depth.  Analysis was completed at the Ohio State University Piketon Crop, Soil and Water Analysis Laboratory and measured bulk density (pb), total porosity (ft), macro and micro aggregate ratio (AR), soil microbial biomass (SMB), ratio of microbial biomass over total organic carbon (SMB:TOC), soil pH, electrical conductivity (Ec), total organic carbon (TOC), particulate organic carbon (POC), passive organic carbon (PC), and active organic carbon (AC).  SMB was determined by a rapid microwave extraction method (Islam and Weil 1998a). TOC content was measured on finely ground soil by using a rapid microwave digestion and colorimetric method (Islam and Weil 1998b). AC was determined based on 2 minute shaking of 5 g air-dried soil with 0.02M neutral KMnO₄ (Weil et al. 2003). PC was calculated by subtraction of AC from TOC. For AR, a sample of 2 mm sieved air-dried soil was passed through a 250 µm mesh by using a wet sieve shaker. Aggregates retained on 250 µm sieve were then collected as macroaggregates, air-dried at room temperature and weighted. Soil pH was measured in a 1:1 using a glass electrode. Ec was determined by a conductivity meter. Soil bulk density (pb) was determined by the core method. The mass of TOC, SMB, POC, AC, and PC was calculated by multiplying their concentration with sampling depth and concurrently measured pb. All the results were expressed on the basis of oven-dried (~105 degree C) weight of soil.

Soil quality data was analyzed by the ANOVA process of the SAS (SAS 2001).  Crop yield data was analyzed by the ANOVA of process (Mullen 2008).

Results

Results indicate that gypsum treatments had significant effect on select soil biological, physical and chemical properties.  The concentration of SMB, the SMB:TOC ratio, and the AR were found significantly influenced by gypsum treatment, especially at the 2 ton per acre treatment level.  No significant response on pb and ft was measured as a result of gypsum treatments.  Soil pH and Ec did not change significantly in response to gypsum treatments.  Although the AC concentrations increased significantly with gypsum treatments over control, the concentrations of TOC, POC and PC did not change.

 

Gypsum Treatment	AR	SMB	SMB:TOC
		mg kg-1	g 100g-1
Control	2.87	237.3	0.98
1.0 Ton per acre	3.19	258.2	0.99
2.0 Ton per acre	3.52	353.9	1.35
ANOVA P > F	0.011	0.054	0.048
AR = macro and microaggregate ratio, SMB = soil microbial biomass, SMB:TOC = ratio of soil microbial biomass over total organic carbon

Table 1. Effect of gypsum treatment on biological and physical properties.

 

Gypsum Treatment	TOC	POC	PC	AC
	g kg-1	g kg-1	g kg-1	mg kg-1
Control	24.3	7.2	23.6	688.0
1.0 Ton per acre	26.1	8.3	25.2	918.7
2.0 Ton per acre	26.3	8.7	25.4	910.6
ANOVA P > F	0.562	0.272	0.481	0.044
TOC = total organic carbon, POC = particulate organic carbon, PC = passive organic carbon, AC = active organic carbon

Table 2. Effect of gypsum treatment on organic carbon factors.

 

Crop yields were not found to be statistically significant (P level 0.05) in any single crop year or crops grown on the gypsum treated plots compared to the control.  Crop yields were collected in years following the soil quality analysis to determine if the significant difference found with select soil quality characteristics from the gypsum applications had a delayed effect on crop yields.

 

Gypsum Treatment	2004	2005	2006	2007	2008	5-year average
Control	39.2	39.3	37.7	39.2	26.1	36.3
1.0 Ton per acre	39.9	39.8	37.8	38.2	25.5	36.2
2.0 Ton per acre	39.6	39.1	37.0	38.4	24.6	35.7
LSD (0.05) = NS

Table 3. Effect of gypsum treatment on soybean yields in bushels per acre.

 

Gypsum Treatment	2004	2005	2006	2007	4-year average
Control	157.2	51.4	36.4	76.4	80.4
1.0 Ton per acre	148.0	55.7	39.1	79.8	80.7
2.0 Ton per acre	148.9	49.3	34.6	67.8	75.2
LSD (0.05) = NS

Table 4. Effect of gypsum treatment on corn yields in bushels per acre.

 

Gypsum Treatment	2009
Control	74.2
1.0 Ton per acre	73.2
2.0 Ton per acre	74.8
LSD (0.05) = NS

Table 5. Effect of gypsum treatment on wheat yields in bushels per acre.

 

Discussion

Gypsum as a soil amendment in this study did not show a significant yield effect during 2004-2009 across the crops of corn, soybean and wheat.   Gypsum as a soil amendment in this study had a significant influence on some soil quality measurements.  The short-term effects of gypsum on SMB, POC and AC contents indicate a biological response to the soil that can contribute to improved soil quality.  SMB includes the smallest living organisms such as bacteria, fungus, protozoa, algae, actinomycetes, nematodes, and nonliving organisms that act as bio-catalyst for organic matter decomposition and mineralization, soil fertility, and humus formation and soil aggregation. POC and AC pools suggest that a small but labile fraction of TOC may respond consistently as early indicators to the effects of the gypsum applications. POC and AC are portions of total soil organic carbon that are relatively easily metabolized or utilized by microorganisms. A significant effect on AR suggests an early indicator of soil quality enhancement from the gypsum treatments and is a positive indicator of soil quality related to improved soil structure relative to soil aggregates.  Soil aggregates are the primary soil particles (sand, silt and clay) held together in a single mass or cluster.  Macroaggregates are soil clusters greater than 250 µm while microaggregates are less than 250 µm.  A favorable shift toward a greater macroaggregate portion compared to the microaggregate portion can positively influence water infiltration and soil structure in clay soils. The impact of gypsum on soil biological, physical and chemical properties should be considered when gypsum is used as a soil amendment.

Literature Cited

Chen, L., Dick, W.A. 2011. Gypsum as an Agricultural Amendment - General Use Guidelines.  Bulletin 945.  Retrieved from http://fabe.osu.edu/sites/fabe/files/imce/files/Soybean/Gypsum%20Bulletin.pdf  The Ohio State University, Columbus, OH.

Dontsova, K., Lee, Y.B., Slater, B.K., Bigham, J.M. 2005. Gypsum for Agricultural Use in Ohio - Sources and Quality of Available Products.  Factsheet ANR 20-05. Retrieved from http://ohioline.osu.edu/anr-fact/0020.html. The Ohio State University, Columbus, OH.

Hoorman, J., Aziz, I., Reeder, R., Sundermeier, A., Islam, R. 2011. Soil Terminology and Definitions. Factsheet SAG-19-11 or AEX 514-11. Retreived from http://ohioline.osu.edu/sag-fact/pdf/0019.pdf.  The Ohio State University, Columbus, OH.

Islam, K.R. and R.R. Weil .1998a. A rapid microwave digestion procedure for spectroscopic measurement of soil organic C. Commun. Soil Sci. Plant Anal. 29:2269-2284.

Islam, K.R. Islam and R.R. Weil .1998b. Microwave irradiation of soil for the routine measurement of microbial biomass C. Biol. Fert. Soils. 27: 408-416.

Magdoff, F., Van Es, H.  2009.  Building Soils for Better Crops. 3^rd Ed.  Sustainable Agriculture Publications, Waldorf, MD.

Mullen, R. 2008.  Ohio State University Extension Excel-Based ANOVA Generator for Analyzing Research Results.  http://agcrops.osu.edu/specialists/fertility/other-information/ANOVAS.xls  Columbus, OH.

SAS Institute.  2001. SAS Statistics Users’ Guide R. 8.2 SAS Institute. Cary, NC.

U.S.D.A.  1999. United State Department of Agriculture Soil Quality Test Kit Guide. Washington D.C.

USDA-Natural Resources Conservation Services. 2014. Web Soil Survey of Defiance County, Ohio and Official Soil Series Descriptions. http://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm

Weil, R.R., K.R. Islam, M.A. Stine, J.B. Gruver and S.E. Sampson- Liebig. 2003. Estimating active C for soil quality assessment: A simplified method for laboratory and field use. Amer. J. Altern. Agricult. 18:3-17.

 

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