Studies were established in five corn-soybean fields in east central Michigan to evaluate the potential benefits of lime and gypsum on soil quality factors and crop production at a large scale. Soil quality measurements included soil bulk density, aggregate stability, infiltration rate and calcium:magnesium ratio. Lime was applied in two fields at 0, 2, 4 or 8 tons per acre. Gypsum was applied in three fields at 0, 700, 1400 or 2800 pounds per acre. Lime application improved soil pH, soil calcium and Ca:Mg ratio, but had little effect on bulk density, infiltration. Aggregate stability was improved in 2 of 3 sampling years. In 3 of the 6 site-years, lime application improved corn or soybean yield. Gypsum application resulted in no to modest increase in Ca:Mg ratio, no effect on soil pH, soil bulk density or infiltration rate, and no effect on corn or soybean yield in 8 site-years. Lime application showed potential for long-term economic benefit. Gypsum application resulted in a negative economic effect due to the cost of the material and spreading without any yield increase.
Interest in the use of calcium from lime or gypsum to improve soil quality has increased in recent years. Use of gypsum has been shown to be highly effective in improving soil aggregation and permeability in high sodium soils in western parts of the United States. Those conditions do not exist in soils of the Great Lakes region. However, there is some concern that a narrow calcium : magnesium ratio may also contribute to reduced soil aggregate stability and soil permeability. Numerous studies in region have documented that maximum crop years can be produced over a wide range of calcium : magnesium ratios. Despite these findings calcium is being promoted to improve soil quality, especially soil aggregation and permeability. This project was initiated to evaluate the effects of lime and gypsum soil quality factors and yield when applied to farm fields in east-central Michigan.
Demonstrate the effects of calcium amendments on soil quality and corn/ soybean yields.
Establish a database for advising farmers regarding the benefits of using calcium soil amendments.
Facilitate measurement of soil quality factors in farmer-initiated field experiments with calcium amendments.
Establish a total of six farmer cooperator fields with calcium treatments for intensive study of effects on soil quality properties and corn yield.
Provide advice and yield analysis for other farmer-managed lime/gypsum demonstration sites in Mid-Michigan.
Enhanced awareness of the effects of calcium, lime and gypsum in soil quality.
Enhanced awareness of soil and watershed quality issues.
Field studies were established on five farms. A randomized complete block design was used in each study field. Four rates of either limestone or gypsum were applied in 45 foot wide strips across the selected fields. The sets of four rates were replicated 6 to 10 times. Calcitic limestone was applied at 0, 2, 4 and 8 tons per acre. The two fields receiving the lime were established in 2000. Gypsum was applied at 0 700, 1400 and 2800 lbs per acre. One of gypsum treated fields was established in 2002 and two were established in 2004 (Table 1). All fields were chisel plowed in the fall of each year. Soil samples, 0 – 8 inches, were collected periodically to document changes occurring in the chemical and physical properties of the soil. Three inch diameter soil cores were collected from the 1 to 4 inch depth for determination of bulk density. Six inch squares of soil were collected to a depth of 4 inches for determination of aggregate stability. The soil was gently broken into pieces and air dried prior to sieving into aggregate sizes of < 2, 2 - 4, 4 – 6.3, 6.3 – 9.5 and > 9.5 mm. The aggregates were wet sieved with gentle up-down action to determine stability. Water infiltration measurements were made using a double ring setup. The soil was saturated before measuring the rates of infiltration. Yield data was collected with yield monitors when combining a swath in the middle of each strip.
Soil pH, Calcium, Magnesium and Ca/Mg Ratio:
Application of 2, 4 or 8 tons calcitic lime per acre on the Armstrong Farm (Celina loam) changed the soil pH from 6.34 to 6.79, 7.01 and 7.49 from 2000 to 2006. These values are just slightly lower than in 2005. The exchangeable calcium level changed from 852 to 1016, 1124 and 1353 ppm, respectively, with the three lime rates. The exchangeable magnesium level was not affected, but the Ca:Mg ratio did increase from 3.88 to 4.34, 5.31 and 6.29 during this time period with the three rates of lime. From 2005 to 2006 the magnesium values decreased more than the calcium values so that the Ca:Mg ratio continued to increase. In the Hammond field the changes in pH (6.54 to 7.22) and Ca:Mg ratio (4.67 to 5.62) with 8 tons lime applied were very similar to the changes that occurred in the Armstrong field.
In the Hanchent field (silty clay loam)application of gypsum (2800 lbs/a) had little effect on the calcium and magnesium levels during the first 8 months after application. After 18 months the magnesium level declined resulting in an increase in the Ca:Mg ratio from 3.43 to 3.81.
Six months after application of 2800 lbs gypsum per acre to the “Mine” field in the spring of 2004, the calcium level increased and the magnesium level decreased. Therefore, the Ca:Mg ratio was increased (Table 6). However, in the fall of 2005 (18 months after application) the calcium and magnesium levels were statistically similar.
Soil bulk density in the top four inches of the soil was not appreciatively affected by the application of lime or gypsum. A significant change took place in only one of the five study fields (Table 2). In the Hammond field the average bulk density was lower, 1.33 g/cm3, where 8 tons lime per acre was applied than where no lime was applied, 1.38 g/cm3. In the Armstrong field the soil bulk density six years after lime application averaged 1.39, 1.38, 1.40 and 1.41 g/cm3 respectively with 0, 2, 4 and 8 tons lime per acre applied. Application of 2800 lbs gypsum per acre in the Hanchett field did not change the soil bulk density during 18 months, 1.36 compared to 1.35 g/cm3 without gypsum. Three years after application of 2100 lbs gypsum per acre the average bulk density was 1.43 in the Taylor field compared to 1.44 without gypsum, and in the Mine field the comparative values were 1.28 and 1.26 g/cm3.
Aggregate stability is the ability of the soil to retain its arrangement of the solid and void space when exposed to different stresses arising from processes such as tillage, traffic, wetting or drying. Aggregate stability was measured on samples collected from the Armstrong field where lime was applied in 2000, and from the Hanchet field where gypsum was applied in 2004. In 2005 aggregate stability was measure directly on air dry aggregates or on aggregates that had been pre-conditioned by humidification. Wet sieving of pre-moistened aggregates more closely simulates field conditions. Direct wet sieving of air-dry aggregates (slaking method) is a harsher test of their stability. When aggregates were pre-moistened, the aggregate stability appeared similar in both the untreated soil and in soil receiving 8 tons lime per acre. Stability of various size aggregates, measured with the slaking method, indicated better stability for aggregates in areas treated with 8 tons lime/A compared with aggregates not receiving lime. The relative mean weight diameters were near 0.2 and 0.3, respectively, across the aggregate sizes 2 to 4 mm, 4 to 6.3 mm, 6.3 to 9.5 mm and > 9.5 mm. In subsequent stability measurements the slaking approach was used. Mean weight diameter was calculated as follows:
MWD = sum (xiwi)
Where xi is the mean diameter of the aggregate size ranges retained on each sieve and wi is the weight fraction or percentage, based on the total oven dry weight of the original aggregates which were recovered in that size range. Units for MWD are mm. Five years after lime application in the Armstrong field MWD was 23% larger where 8 tons lime per acre was applied. However, in 2006 the MWD was 14% smaller where the lime was applied.
Gypsum application in the Hanchett field did not improve the MWD. With 2800 pounds gypsum per acre the average MWD was 2.98 mm compared with 3.45 mm without gypsum being applied.
Water infiltration measurements were taken only in the control and high rate of lime or gypsum strips. Infiltration rates were quite variable among the three clustered measurement sites within each treatment strip location. The CV values ranged from 50 to 62%. Hence, differences were hard to evaluate and no reliable differences occurred. In the Armstrong field the average infiltration rate in each strip ranged from less than 0.5 inch water per hour to near 4 inches per hour. When compared across 6 replications the overall average infiltration rate was 2.30 inches per hour for the untreated strips and 2.28 for the strips receiving 8 tons lime per acre. In the Mine field the range of values was similar to those observed in the Armstrong field. Across four replications of closely paired strips the infiltration rate in the untreated strips was 1.83 inches per hour compared with 2.84 inches per hour in the strips receiving 2800 lbs gypsum per acre. This appears to be positive improvement resulting from gypsum application. However, statistically there is only 60:40 chance that the difference is due to the application of gypsum rather than natural variability. In the Taylor field the infiltration rate was 2.16 inches per hour in the untreated strips compared to 1.58 inches per hour in the strips receiving 2800 lbs gypsum per acre.
Application of calcitic lime resulted in an increase in soybean yield in two of the four site-years and an increase in corn yield in one of the two site-years. The soybean yield with 8 tons per acre was significantly greater than with no lime applied in 2004 at the Armstrong (6.9 bu/a) and Hammond (3.1 bu/a) sites. Where 2 and 4 tons/a were applied the yields were intermediate and not different from either the control or 8 tons/a treatment. In 2005, corn yield was increased in the Armstrong field with all three rates of lime.
Corn and soybean grain yields in the Hanchent (HAN), Mine (MIN) and Taylor (TAY) fields during the years of this study were similar across all gypsum rates within each field. Lime application appears to have more potential for yield benefit than does application of gypsum.
A “Soil Quality Field Day” was held in July, 2006 in the Mine field of the Jacobs farm. A trench was dug across the control strip and the strip receiving 2800 lbs gypsum per acre to examine the soil structure, resistance to a penetrometer and infiltration rate. In the demonstration areas differences in these soil properties were not distinguishable. Those attending received a update on the results of the study sites along with information on how lime and gypsum may benefit the quality and productivity of soils. Additional information was presented on improving soil quality with manures, crop rotations and cover crops by two MSU researchers. The farmers attending farm 10,000 acres. As the result of the findings in these field studies interest among farmers in applying gypsum has decreased. At the beginning of the project most farmers in the Genesee, Livingston, and Shiawassee counties area of Michigan were interested in gypsum application. Now few farmers are interested, but interest in lime application is still strong.
The two primary mechanisms for positive economic impact are through yield enhancement and cost reduction. For Michigan soils, lime application has better potential for economic benefit than gypsum application. Lime application provide a positive yield effect in about 50 percent of the site-years. Lime spread costs 20 to 25 dollars per ton. A 3 bu/a soybean yield increase adds $28.50 dollars per acre at $9.50 per bushel. An 8 bu/a corn yield increase at $3.75 adds $30 per acre in income. Lime is normally thought of as a long-term investment, but where yields are increased as occurred in the Armstrong the cost of 2 ton lime per acre can be recovered in 2 to 3 years. In these studies gypsum application had no effect on corn or soybean yield.
Gypsum application had only a modest effect on the calcium to magnesium ratio and no effect on crop yield. The economic benefit from this project is in not applying gypsum for those Michigan farmers that are considering the practice or are having it recommended to them. The cost of mined gypsum is 30 to 35 dollars per ton spread. The cost of by-product gypsum is much less, 10 to 15 dollars per ton spread. Unless there is a proven need for calcium or sulfur based on a soil test, application of gypsum will have a negative economic impact. Even at 1000 lbs/a application of gypsum will result in a loss of 5 to 17 dollars per acre.
Consultants in the area of this study indicate farmers’ interest in applying gypsum has decreased in favor of lime application. In this regard the farmers are accepting of the results of this study and the results are having an impact.
Educational & Outreach Activities
Four educational meetings and one field day were held. No publications have been published to date. A Research Report and an Extension bulletin are expected in 2008.
Areas needing additional study
There is still a need for controlled field studies on the effects of lime and gypsum application on infiltration. When done on a field scale the variability overshadows any possible treatment effects.