Why Use Aglime?

Aglime and Crop Production
Application of Aglime Helps Correct Nutrient Problems Caused by Soil Acidity
Aglime, properly used, contributes to higher crop production. It lowers the acidity (raises the pH) of the soil and minimizes the adverse effects of high concentrations of soluble aluminum, iron and manganese on crop growth, effects that are associated with acid soil conditions. Soluble aluminum aggravates soil acidity by causing the release of free hydrogen from soil clay and organic matter particle surfaces during hydrolysis.

Iron and aluminum, in the soluble state, both react with phosphorus to form insoluble aluminum and iron phosphates, a process that can seriously reduce the availability of this necessary plant nutrient to the crop. Reduced crop growth and yield and lowered fertilizer efficiency are the usual results. High soluble manganese levels, which are associated with acid soils, promote "luxury consumption" of elemental manganese and toxicity in manganese- sensitive crops such as cotton, potatoes and soybeans. Maintenance of the proper soil pH with the application of aglime will correct or prevent these low-pH related problems.

Maintenance of soil pH at agronomically acceptable levels with the regular application of aglime assures that soil calcium or magnesium depleted by leaching, erosion and/or crop removal will be returned to the soil. Regular application also promotes better overall availability of those nutrients essential for healthy crop growth, improves the ability of growing crops to utilize them, and increases the efficiency of high cost fertilizers. The availability of the various plant nutrients is affected somewhat differently by changes in soil pH (see Figure 3-1). Primary nutrients will increase in availability with an increase in pH to approximately 6.0-7.0, while the micronutrients, with the exception of molybdenum, decrease in availability. Agronomists generally agree that a soil pH of approximately 6.5-6.9 is optimum, as it provides "the best of all worlds" from the nutrient availability standpoint.

Soil pH Management Critical in Conservation Tillage Farming
All conservation tillage systems are designed to reduce the number and frequency of tillage operations performed when preparing a field for planting. A characteristic common to these farming methods, therefore, is that the soil is typically worked or disturbed to a shallower depth, usually to no more than two to four inches, as compared with conventional tillage where the soil may be completely inverted to a depth of eight to ten inches or more.

As a result, continuous use of conservation tillage encourages the accumulation of fertilizer, herbicide, and crop residues in the surface layers of soil, which help to create strongly acid conditions in the soil zone where the crop will be planted. As a case in point, it has been demonstrated in field trials in Pennsylvania and Kentucky respectively (see Tables 3-1 and 3-2) that application of nitrogen under no-till conditions can cause reductions of up to two full pH units in surface soil pH, depending upon the nitrogen used and the rate of application. Similar trials in Maryland have demonstrated that under no-till conditions the application of 160 tbs. of actual nitrogen per acre applied to corn can cause reductions of up to 1.5 pH units at the soil surface within a matter of a few weeks.

Soil acidity increases of this magnitude contribute to a number of factors that can limit crop yields and cause significant income losses to the farmer, such as:
reduced availability of many essential nutrients required by crops for growth to harvestable maturity.
increased solubility of certain micronutrients and aluminum to soil levels toxic to crops.
reduced activity of beneficial soil microorganisms and increased activity of disease-producing ones that thrive under acid soil conditions.
significant yield losses due to heavy weed infestations at harvest time, the result of poor triazine herbicide performance under acid soil conditions.

These problems are associated with soil acidity generally. They are accentuated in soils farmed using conservation tillage practices. A well planned and executed liming program is the most effective means available to the farmer for eliminating these problems. Farmers should be aware that aglime moves very little in the soil without mechanical mixing. The tendency of aglime applied under conservation tillage conditions is to remain at or near the soil surface. Therefore, it is important that desired pH levels are achieved by liming the top six to ten inches of subsoil before putting a field on a conservation tillage program.

Table 3-1

Soil pH of surface inch produced by various nitrogen materials after five years. N applied at 180 lbs. N/Acre/Year -Pennsylvania.
N Source and Soil pH

Control	UREA	28% N Soln	Am. Nitrate	Am. Sulfate
6.7	5.9	5.8	5.5	4.7

Table 3-2

Effect of Five Years Continuous Corn on Soil pH

Starting pH	No N	75 Lbs N/Acre/Yr	150 Lbs N/Acre/Yr
5.3	5.2	4.8	4.6

Benefits of a Good Liming Program Go Beyond Its Effects on Soil Fertility
Proper pH maintenance also has other beneficial effects. The effectiveness of certain herbicides, especially the triazines-i.e.: atrazine, metribuzin (Sencor, Lexone) and cyanazine (Bladex), is enhanced when the soil pH is maintained above 6.0-6.2.

Because beneficial soil organisms tend to be more active in a neutral (7.0) or near-neutral soil (see Table 3-3), the process of organic matter decomposition, a factor in soil aggregate formation, with its associated improvement in soil aeration and drainage, is accelerated. The root nodule bacteria responsible for nitrogen fixation in legumes also function best under these conditions.

Table 3-3

Relationship of Soil pH to Soil Microbial Activity

pH	Reaction	Microbial Activity
<5.0	Strongly Acid	Low-primarily fungi
5.0-6.0	Moderately Acid	Low
6.0-6.6	Slightly Acid	Moderate
6.6-7.4	Neutral High
7.4-8.0	Slightly Alkaline	Moderate
8.0-9.0	Moderately Alkaline	Low
>9.0	Strongly Alkaline	Very low-primarily bacteria

Agronomic Benefits Readily Translate into Increased Dollar Returns to the Farmer
The cost effectiveness and return the farmer can realize on his expenditure for aglime as a result of these agronomic effects become apparent upon examination of yield data produced during research trials at various U.S. locations.

For example, in a University of Wisconsin trial involving alfalfa, increasing the soil pH by applying aglime raised both the tonnage yield and protein content of the forage and significantly increased the cash value of the crop in the process.

Similarly, soybeans, another legume, will show dramatic response to liming when the need exists. For example, in a Kansas field trial (see Table 3-4), the application of aglime increased soybean yields by 12.6 bushels per acre where no fertilizer was applied, and by 11. 1 bushels per acre in plots to which fertilizer was applied according to soil test recommendations. For a commercial soybean producer in this situation, one aglime application would start paying for itself in the first crop year following application. In addition to these Wisconsin and Kansas results:

Similar response to aglime has been observed in recent years in other states in various commercial and experimental fields planted to continuous corn. In a series of continuous corn plots established at Washington Court House, OH, use of aglime significantly increased the incidence of grain yields in excess of 140 bushels per acre under conditions of both low and high fertility (see Table 3-5).

In a recent survey conducted by the Potash and Phosphate Institute, of 549 producers in 33 states who achieved grain yields of 200 bushels or more per acre, soil test results showed that all but two, or over 99 percent of the fields reported in the survey, had pH levels of 6.0 or higher.

Table 3-4

Soybean Response to Liming

Treatment	Yield Bus/A	Increase Due To Liming-Bus/A
No Lime, P, or K	15.7
Lime Applied, No P or K	28.3	12.6
No Lime + 0-150-150	35.1
Lime Applied + 0-150-150	46.2	11.1

Aglime at the rate of approximately one ton per acre increased yields of seed cotton an average of 502 lbs. per acre at 10 widely scattered southeastern U.S. locations. Unlimed soil pH for the 10 locations averaged 5.1 and ranged from 5.0 to 5.4 (see Table 3-6).

Aglime is recognized as very important to soybean production in the southern states. According to Dr. John B. Henderson, Auburn University, AL, "Despite progress in the application of lime during the past few years, low soil pH remains one of the most limiting factors in soybean production in Alabama. A large percentage of soybean production problems diagnosed during the growing season is directly or indirectly related to low soil pH." In soybean field studies in the state, yield increases averaging 11 bushels per acre were obtained where aglime was applied on low pH soils. In the adjoining state of Mississippi, yield increases averaging 10 bushels of soy beans per acre were obtained in field experiments where lime was applied to acid soil. Soil test data from the southern states accentuates the problem: in a survey of 11,000 soil samples taken from Alabama soybean fields from July 1, 1979 to June 30, 1980, 37 percent of them showed a need for lime, and in a survey of 113 sampled soybean fields in Georgia, two-thirds of them were below the optimum pH range of 6.0-6.5.

Table 3-5

Corn Response to Lime at High and Low Soil Fertility Levels

Soil pH of acid Plots-5.0-5.5
Limed plots receive annual applications of aglime at rates necessary to adjust and maintain soil pH at 6.5. Each plot divided into 16 equal-size sub-plots for statistical data collection. (Agrico Chemical Company, Washington Court House, Ohio, 1980.)

Plot	Soil Test Situation	Avg. Corn Yield Bu/A	No. Out of 16 Plots Exceeding 140 Bu/A
1	acid, low P-K	101	1(6%)
2	limed, low P-K	127	5 (31%)
3	acid, high P-K	145	11(69%)
4	limed, high P-K	152	16(100%)

Table 3-6

Yield-Lbs Seed Cotton/Acre

pH of Unlimed Soil	Unlimed	Limed	Yield Increase
5.1	1,430	1,932	502

The preceding data speaks for itself. Similar examples attesting to the agronomic and economic value of aglime to production agriculture are plentiful. Regular application of aglime based on soil test recommendations makes good agronomic and economic sense for the profit-minded farmer.

Specialists in commercial tree production agree that the best approach to pH management in these types of operations is to control subsoil pH at the time of planting. The soil pH in these situations should then be monitored annually by soil analysis and aglime applied in conjunction with a good legume cover crop program to raise the soil pH to 6.0 - 6.5.

Liming pays in many ways- in extra bushels and tons of crops, in healthier, more profitable livestock, in the worth of properly limed land, and from the satisfaction that comes from doing a better job of farming.

FOR MORE INFORMATION ON AGLIME AND ITS BENEFITS, CONTACT THE NATIONAL STONE ASSOCIATION AT THE ADDRESS LISTED BELOW.

--Chapter 3 of the Aglime Fact Book- Courtesy of the National Stone Association.

The information on Aglime is Courtesy of the National Stone Association. © 1986. Used by permission.

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