University Reseach

The benefits of gypsum use in agricultural production have been studied for many centuries. Recent research continues to substantiate earlier studies as well as find new benefits to gypsum use. In this section we will try to present some of this data in a concise format.

Benefits of gypsum include:

Improving soil structure
Amend sodium affected soils
Improve soil infiltration
Decreases the swelling of clays
Offsets affects of aluminum toxicity in low pH soils
Helps curb phosphorus runoff from soils
Improves quality of several fruit and vegetable crops
Is an excellent source of plant available calcium and sulfur
Increases iron uptake by reducing the detrimental effects of bicarbonates

Serves to decrease the bulk density of soils
Useful tool in decreasing the negative effects of high magnesium in soils
Increases the efficiency of nitrogen applications
Increases the availability of potassium already present in the soil
Offsets ill effects of irrigation with poor quality water
Can serve as a tool to enhance iron, manganese and zinc availability
Aid to stop soil erosion
Decreases incidence of some diseases
and more

Improve Infiltration

When gypsum provides any one of the above benefits higher yields can be realized. The National Soil Erosion Laboratory at Purdue University in West Lafayette, IN has performed many research projects (Dr. Darrell Norton, et.al.) showing the benefits of gypsum on increasing water infiltration and improving soil structure. As the data shows, gypsum greatly increased the infiltration in soils from Ohio, Indiana, Illinois and Iowa (from left to right).

This researcher also showed that much of the increase in infiltration was dued to less surface sealing as a result of the application of gypsum. Rain water has low amounts of electrolytes. Consequently the soil particles will tend to swell and this causes replulsion between clay particles. The addition of gypsum increases the bonds between soil particles and soil cohesiveness.

Other research has also shown that percolation rates of water increase with the use of gypsum as is shown in the data below.

Treatment	Standing after 24hrs., In.	ml/24 hrs.
check	50	86
Sulfur, 1 ton	23	86
CaSO4, 1 ton	18	190
Ca SO4, 5 tons	15	280

Amend Low pH Soils

Dr. Malcolm Sumner, et.al. at the University of Georgia has shown that gypsum is highly effective as an ameliorant for low pH soils that have high levels of exchangeable aluminum. His research revealed that even 16 years after the initial application of gypsum the yields of both corn and alfalfa were higher where the gypsum was applied.

Corn Expt. 1Bu/A	Corn Expt. 2Bu/A	Alfalfa T/A
Control	107	105 – 2.39
Gypsum	161	135 – 4.06

It is theorized that the gypsum reacts in these low pH soils to form ion pair AlSO4 which renders the aluminum non-toxic to plant roots. The calcium in the gypsum is also thought to create a better balance between aluminum and calcium in soil solution.

A benefit of finely ground gypsum is that it is 200 times more water soluble than lime and so calcium will move more easily downwards through the soil profile. In one study water soluble calcium was increased to a depth of 36 inches in a silt loam soil in just two years.

Increase Nitrogen Efficiency

Corn

The Ohio State University (Dick, Chen & Kost) has conducted a study in which they measured the response to adding gypsum to the fertilizer program to increase nitrogen efficiency in corn. As the results below indicate the 120# rate of nitrogen with 200# of gypsum produced a significantly higher yield than the 180# nitrogen rate by itself. This could be due to a nitrogen/sulfur interaction, a calcium/nitrogen interaction or simply a gypsum/nitrogen interaction. These soils were silt loam soils and had a pH near neutral.

This would support the idea of a more balanced fertility program to produce higher yields rather than just increasing nitrogen rates as some have suggested.

Corn Yield, Bu/A
N Rate	0#	60#	90#	120#	150#	180#
2003
No Gypsum	126	160	161	183	182	189
200# Gypsum	148	179	180	191	191	205
2004
No Gypsum	104	128	147	160	169	171
200# Gypsum	121	148	157	188	166	161
2005
No Gypsum	65	66	76	89	117	98
200# Gypsum	60	89	85	131	110	84
Avg. 3 years
No Gypsum	98	118	128	144	156	153
200# Gypsum	110	139	141	170	156	150

Alfalfa

Alfalfa is a crop that has a high demand for both calcium and sulfur. Research conducted at The Ohio State University by Dr. Warren Dick et.al. has shown that alfalfa responds very well to gypsum and that a one ton rate will give a response for at least three years. Dr. Dick has commented in a personal conversation that you see a response in alfalfa nearly every time noting that the response is consistent.

Recent research at Iowa State University has also revealed that alfalfa is quite responsive to calcium sulfate. Interestingly enough the response was observed on both low yielding alfalfa and high yielding alfalfa sites. The average response was over 1 ton/acre just like that observed in Ohio.

*Tons/Acre
Treatment	West Union	Wadena	Waukon	Waucoma	Nashua
Untreated	0.78	1.32	1.39	1.85	6.75
Gypsum	1.07	2.92	3.58	3.24	7.14

GYPSUM WAS APPLIED IN APRIL AT NASHUA AND MAY AT OTHER LOCATIONS. STUDY WAS DONE IN 2006.

*Tons/Acre - Northeast Iowa Study 2005-2006
Treatment	2005-Cuts 2 & 3	2006-Cut 1
Untreated	1.18	1.1
Gypsum	2.49	2.14

ALFALFA IN UNTREATED WAS SHOWING YELLOWING TYPICALLY OF SULFUR DEFICIENCY. PLANT SULFER LEVELS WERE .14% IN UNTREATED AND .41% IN GYPSUM.

University of Minnesota has also compared responses of alfalfa to lime and gypsum. They reported a response to both materials. Again the response to gypsum in alfalfa was over 1 ton/acre as is shown below.

Treatment	Yield, T/A
Untreated	7.66
Lime (2 T/A)	8.27
Gypsum	8.84

Other Forages

Other forages have also been proven to be responsive to the use of gypsum as well. Research in Northern California by University of California researchers have shown yield increases in Subclover-grass pastures over three years from an initial application of 1500# of gypsum.

Hay Yield of Subclover-grass*

*Average annual yield over three years.
Treatment	Site #1	Site #2
None	1.16 T/A	1.09 T/A
1500# Gypsum	1.65 T/A	1.73 T/A

A study by Univ. of New Jersey also has shown that Timothy and Rye grass also have proven to be responsive in a soil where 2 ton/A of gypsum was applied to improve drainage and soil structure.

*Average annual yield over three years.
Treatment	Timothy	Rye
None	1.84 T/A	1.58 T/A
Gypsum	3.05 T/A	2.01 T/A

A study at Penn State also has shown a significant increase in root growth by both tall fescue and bermuda grass when gypsum was applied to a clay soil. As you can see in the picture below the gypsum treated soil had a larger amount of root mass at each depth than the control.

As you would expect, this also correlated to increased plant growth as well as is indicated by the increased clipping weight that is shown.

Improve Nutrient Uptake

The use of gypsum has shown to increase nutrient uptake and consequently increase yield. The University of Nebraska studied iron chlorosis and found that when they placed gypsum in the row or banded gypsum that they were able to significantly affect iron chlorosis and also increase yield in soybeans (see table below). Although not completely understood, it is theorized that either the calcium is fixing the bicarbonates in these soils or the sulfate sulfur is reducing the uptake of the bicarbonates or a combination thereof.

**Band is 3 inches deep and 1.5 inches to side of row.
Treatment	Rate,Method	Yield, Bu/A
1982
Check	0, In Band by Row	25
Gypsum	450#, In Band by Row	44
1983
Check	0, In Row at Planting	19
Gypsum	75#, In Row at Planting	30

Research in a laboratory study at USDA/ARS in Colorado (Olsen & Watanabe) showed that the use of gypsum in six different soils increased the uptake of iron, manganese and zinc in the plant significantly and increased the growth of grain sorghum by as much as 10 fold. The mechanism by which CaSO4 increases iron, manganese and zinc concentrations is unknown. They theorized an interaction with molybdenum or possibly ion-pairs being formed between sulfate sulfur and these elements.

Vegtables

Research has also shown that vegetable crops are very responsive to the use of gypsum both in yield and quality.

Cantalope

The study from the University of Georgia shows that cantaloupe benefited from the use of gypsum.

Treatment	Yield, T/A	Skin Ca%
Control	2.99	1.07
Gypsum (.56 T/A)	4.54	1.24

Tomato

A Mississippi study revealed that tomato yield and quality is also greatly improved with the use of calcium sulfate.

Most of this can be attributed to better calcium nutrition observed by the higher skin calcium levels.

Treatment	Yield, T/A	Skin Ca%
Control	26.5	0.21
Gypsum (2 T/A)	37.5	.34

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