KGS Home Geology Home

Kansas Geological Survey, Bulletin 204, pt. 1, originally published in 1972

Progress Report: Utilization of Fly Ash in the Reclamation of Coal Mine Spoil Banks in Southeastern Kansas

by William Kovacic and Ronald G. Hardy

Originally published in 1972 as part of Kansas Geological Survey Bulletin 204, pt. 1, p. 29-31. This is, in general, the original text as published. The information has not been updated. An Acrobat PDF version of the complete bulletin (15 MB) is also available.


This research project utilizes bituminous coal fly ash for neutralizing acid soil and/or water on leveled spoil banks. The study program included laboratory testing to determine the proper ratio of fly ash to soil and establishment of experimental test plots in Crawford County, Kansas. Factors such as temperature and rainfall were recorded and soils were tested for other chemicals that could also affect plant growth. In general it was concluded that fescue grew better on soil treated with fly ash rather than with lime, as long as rainfall was adequate.


This paper is a progress report on a segment of continuing research involving mined-land reclamation in Cherokee and Crawford counties in southeastern Kansas. This segment concerns the utilization of coal fly ash for corrective measures in connection with agricultural uses of leveled spoil banks, i.e., neutralizing acid soil and/or water. Considerable work along this line has already been undertaken by staff of the U.S. Department of the Interior, Bureau of Mines, Energy Research Center, Morgantown, West Virginia. There are, of course, differences between West Virginia and Kansas reclamation; one of the most significant is that much of the strip-mining in West Virginia is contour mining, or stripping along the sides of hills. In Kansas, mining is done on an areal basis. Also, acid conditions in West Virginia are more frequent and severe than in Kansas, with the net result that stream pollution is more prevalent in West Virginia than in Kansas.

This study program proceeded along the following general lines. First, in the laboratory, by adding varying amounts of fly ash to the soil, a proper fly ash-tosoil ratio was estimated on the basis of change in pH. Second, suitably sized test plots were laid out to compare the necessary amounts and effects of fly ash versus pulverized limestone on the growth rate of several different types of plantings.

Temperature and rainfall measurements were taken at the plot site and observations were carried on to note growth rates and quality of plant growth. It was found that extremely variable weather affected plant growth. Planting took place in April, 1971, followed by a month of extremely dry weather and then a month of very wet weather.

Determination of Fly Ash Requirement

Fly ash utilized in this study was unmodified, drycollected ash obtained from the Montrose station of the Kansas City Power and Light Company at Clinton, Missouri. The chemical analysis of the fly ash (figures rounded) was as follows: SiO2, 41.3%; Fe2O3, 32.1%; Al2O3, 16.7%; TiO2, 0.8%; CaO, 4.3%; MgO, 0.6%; SO3, 1.0%; K2O, 2.1%; P2O5, 0.3%; Na2O, 0.5%; undetermined, 0.2%. The fly ash pH was 9.8.

Representative samples of soil from the plots were treated in the lab with the fly ash. The fly ash was added in 5-gm increments to seven 100-gm samples of soil to produce soil-to-fly ash ratios of 100-5, 100-10, 100-15, 100-20, 100-25, 100-30, 100-35. Six days after the experiment began, the pH was recorded. The peracre rate of treatment to produce the various pH levels as determined in the lab and the amount required to treat the 25 x 25-foot plots was then computed (Table 1).

Table 1--Soil-fly ash ratios, pH values, and application rates.

Soil-fly ash ratio
pH after 6 days Application rate
per acre
per 25 x 25'
test plot
100-35 8.8 285 8178
100-30 8.5 245 7031
100-25 8.2 204 5854
100-20 7.7 163 4677
100-15 7.3 129 3702
100-10 7.2 82 2353
100-5 6.6 41 1177

Determination of Lime Requirement

The lime requirement was found by taking nine samples from the plot. These were tested to determine pH and buffer pH for each sample. The requirement for effective calcium carbonate (E.C.C.) was then determined. The nine values were averaged to determine the E.C.c. requirement per acre. This figure was reduced to the amount required for a 25 x 25-foot plot, 350 pounds (24,222 pounds E.C.C. per acre). At a lime composition of 65 percent E.C.C., 500 pounds of lime were required for the plot.

Test Plots

The experimental tests plots for fly ash research are located in the northeast corner of a farm owned by Mario Nardelli, Sr., in sec. 15, T 28 S, R 25 E, Crawford County, Kansas (Fig. 1). The area was strip-mined for coal in the 1930's and was partially leveled in 1967 to allow a large power shovel from the Clemens Coal Company to move across the land to a new location. The general appearance of the area was extremely barren. A sterile pit of water borders the west edge of the area. The pH of the water in the pit was 3.1.

Figure 1--Layout of experimental test plots, NW NW sec. 15, T 28 S, R 25 E, Crawford County, Kansas (not to scale).

Layout of experimental test plots

Three 25 x 25-foot plots were laid out in the area that had been leveled. The south plot was used for fly ash treatment with fescue as the crop. The middle plot was used for lime treatment with fescue as the crop. The north plot was used for both fly ash and lime treatment and crown vetch was the crop. The planting schedule is outlined in Table 2.

Table 2--Treatment of test plots.

Treatment Application rate
per 25 x 25'
test plot
per acre
South Plot (fly ash)
Fly ash from KCP&L 3800 lbs 132.0 tons
Fertilizer (6-24-24) 46 oz 200.4 lbs
Seed-Kentucky 31 Tall Fescue 7 oz 30.48 lbs
Middle Plot (lime)
Lime-65% E.C.C. 500 lbs 17.4 tons
Fertilizer (6-24-24) 46 oz 200.4 lbs
Seed-Kentucky 31 Tall Fescue 7 oz 30.48 lbs
North Plot (fly ash and lime)
Strip A, (2 1/2 x 25-foot test plot)
Fly ash 600 lbs 209.1 tons
Crown vetch transplants not determined not determined
Strip B, (2 1/2 x 25-foot test plot)
Neutralizing agent none none
Crown vetch transplants not determined not determined
Strip C, (2 1/2 x 25-foot test plot)
Lime 50 lbs 17.4 tons
Crown vetch transplants not determined not determined
Fertilizer (6-24-24) 46 oz 200.4 lbs

Effect on Soil pH: Fly Ash Versus Lime

Soil samples were taken and pH values were determined before any treatment was made. Nine samples were taken from each plot, each sample consisting of four probes taken approximately 6 inches deep. The effect of the addition of fly ash and lime on soil pH is given in Table 3. The average pH for the fly ash plot was raised from 3.5 to 4.5 and the average pH for the lime plot was raised from 3.6 to 4.4.

Table 3--Change in soil pH of test plots with application of fly ash and lime.

South Plot
(fly ash)
Middle Plot
North Plot
(fly ash and lime)
Before After Before After Before After
1 3.9 4.2 3.6 4.8 3.8 4.8
2 3.4 3.7 3.7 4.4 3.5 4.5*
3 3.5 4.6 3.9 4.0 3.6 4.7
4 3.4 4.2 3.4 4.9 3.8 5.3
5 3.4 4.2 3.4 4.8 3.9 4.5†
6 3.4 6.1 3.7 3.8 3.7 4.5
7 3.5 4.8 3.6 3.8 4.2 5.7
8 3.4 4.3 3.7 4.0 3.8 6.3‡
9 3.9 4.3 3.4 3.9 4.1 4.1
* Lime strip.
† No treatment strip.
‡ Fly ash strip.

Temperature and Rainfall

The weekly temperature range at the plot site was recorded, as indicated by a maximum-minimum thermometer. The minimum temperature, 37°F, was recorded during the first week of experimentation, April 12-1S, 1971. The maximum temperature, 102°F, was recorded the week of August 23-29.

A record of rainfall during the plant-growing period was kept from April 15 to August 30, 1971. Total rainfall was: April, 2.S in.; May, 4.7 in.; June, 4.7 in.; July, 9.5 in.; August, 0.7 in. By comparison, the ten-year (1961-1970) average rainfall for these months was: April, 4.7 in.; May, 6.4 in.; June, 5.9 in.; July, 3.4 in.; August, 3.1 in.

Trace Element Analysis

A qualitative analysis of trace element content of the acid soil of the test plots was made. The fly ash test plot was compared to the lime test plot for trace element content. They were the same, with the following exception: traces of chromium, cobalt, nickel, and zinc were found in the fly ash plot. [Note: Testing was conducted in the Geochemistry laboratory of the Kansas Geological Survey. A detailed analysis is available.]


Because of adverse weather immediately after planting, crop growth was not as vigorous as it could have been; however, all treated plots supported plant growth. There was no growth on the non-treated crown vetch plot.

As long as rainfall was adequate, fescue growth was better on soil treated with fly ash. During prolonged dry periods, fescue on the fly ash-treated plot appeared to be the most adversely affected and began to turn brown. However, it was evident from the appearance of the plots that moisture retention was greater in the soil-fly ash mix than in lime-soil mixes. When rainfall increased after the dry period, fescue planted on fly ash-treated soil again took on a normal green color. Samples of fescue from the fly ashtreated plot are being analyzed for mineral content.

Whether or not fly ash can be utilized in southeastern Kansas will depend largely upon the cost of its application compared to the cost of lime application. A cost analysis of fly ash versus lime application is planned in order to make this comparison.

The results of this segment of the continuing research on mined-land reclamation in southeastern Kansas definitely indicate that application of fly ash to acid spoil-bank soils can alter the soil pH to the extent that production of grasses and legumes is possible on otherwise useless soils.


The assistance from the Kansas Power and Light Company (KP&L) and the Kansas City Power and Light Company (KCP&L) in supplying fly ash for the test plots is greatly appreciated. Mr. Lee Brunton of KP&L and Mr. Pat Tansey of KCP&L were especially helpful.

Kansas Geological Survey, Reclamation of Coal Mine Spoil Banks in Southeastern Kansas
Placed on web March 24, 2016; originally published in March 1972.
Comments to
The URL for this page is