Calcium Inputs for Soil Quality Improvement
Studies are in place in five fields to evaluate the potential benefits of lime and gypsum on soil quality factors and crop production. Application of 8 tons lime per acre and 2800 lbs gypsum per acre has not changed the soil bulk density. Calcium/ magnesium ratio has increased in relation to the amount of lime applied, but has not been changed by the application of 2800 lbs gypsum per acre. Soil aggregate stability analyses on 2005 samples are still in progress. Results from 2004 indicate a slight increase stability with lime application. Infiltration measurements were not able to be taken in the fall 2005 because of very dry soil conditions. Measurements are planned for spring 2006. No major differences in infiltration were seen in 2004. Four educational meetings on soil quality were held for farmers and consultants during the winter of 2005. Preliminary results of this project were presented.
Demonstrate the effects of calcium amendments on soil quality and corn/ soybean yields.
Establish a database for advising farm 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 soil and watershed quality issues.
Enhanced awareness of the effects of calcium in soil quality.
Calcium treatments are in place on five field sites to evaluate and demonstrate the effects of calcium additions on soil quality and crop production. Lime treatments were initially established on one additional field, but it was lost as a study site due to a change in the lease. Table 1 presents information about the lime (two fields) and gypsum (three fields) treatments. Each of the treatments was spread in strips across the fields. The strips were randomly assigned in a randomized complete block design. Each field has six or more replications of the treatments. All fields are chisel plowed in the fall of each year. Soil samples have been collected from plot areas in all fields to track changes in extractable calcium and magnesium values, and the calcium : magnesium ratio, and also soil pH, phosphorus and potassium. In fall 2005, soil cores were collected from three fields to evaluate soil bulk density. Separate samples were collected to evaluate strength of soil aggregates. Water infiltration measurements were taken in two fields in the fall of 2004, but were not able to be taken in fall 2005 because the soil was so dry. These measurements are planned for spring 2006. Crop yields have been determined by yield monitors on the farmers’ combines.
Application of the lime and gypsum has not changed the bulk density of the soils in the three fields where it was measured. Soil bulk density cores were collected only from the untreated and the high rate of lime or gypsum. If there is not a difference between the two extremes, it is unlikely there will be a rate effect. The bulk densities reported are the averages of 21, 39 and 45 paired samples in the ARM, Han and TAY fields, respectively. The other two fields were tilled after harvest before bulk density cores were able to be taken.
Lime application to the Armstrong field has resulted in a marked change in the soil pH, 6.5 with no lime to 7.6 with 8 tons/A. Even though the lime was spread in 2000, the effects were still evident in the fall 2005. Extractable phosphorus, potassium and magnesium values have not been affected. Exchangeable calcium has increased in relation to the lime rate. Hence, the calcium : magnesium ratio now ranges from 3.57 to 5.77, on an equivalents basis. If the calcium : magnesium ratio is important for soil quality and crop yield, it should be observed in this field.
Application of the various rates of gypsum in the Hanchent field has had no effect on soil pH, or any of the extractable nutrient levels. Soil was sampled to 8 inches deep. This is as expected, except exchangeable calcium level should have increased with the amount of gypsum applied. From fall 2004 to fall 2005 the calcium level surprisingly, actually decreased about 150 ppm. The calcium: magnesium ratio was unchanged by the addition of gypsum at both sampling times.
By the fall of 2005, the various rates of gypsum applied in the “Mine” field had not had any effect on exchangeable calcium level or the calcium : magnesium ratio. The 2800 lbs gypsum per acre supplies about 560 lbs calcium per acre. The reason for this lack of increase in extractable calcium is not evident at this time. The 2 tons lime per acre (1200 lbs calcium) in the Armstrong field showed an increase in extract calcium of about 170 ppm five years after application. Maybe the increase will still occur or the rate of gypsum is insufficient to cause significant change.
Soybean yield in the Armstrong (ARM) field in 2004 increased in relation to lime rate, 35.0 vs 41.9 bu/A with no lime vs 8 tons/A. In 2005, corn grain yield was higher where 2 tons lime per acre was applied (156 vs 148 bu/A), but was not affected by the higher lime rates. In 2003, corn grain yield in the Hammond (HAM) field showed a trend toward decreased yield with increasing lime rate, from 113 to 99 bu/A with no lime vs 8 tons/A. Perhaps the higher soil pH reduced the availability of some key micronutrients. Soybean yield the following two years was similar across the lime rates.
Soybean and corn grain yields in the Hanchent (HAN), Mine (MIN) and Taylor (TAY) fields during 2004 and 2005 were similar across all gypsum rates within each field.
During 2006 efforts for this project will focus on collecting key data on infiltration rates in all fields, on aggregate stability, soil bulk density, exchangeable calcium and magnesium levels and the calcium: magnesium ratios. Yield will be collected for all treatments in all fields. A field day will be held to show the field study areas and share information about soil quality and the findings of this project.
Impacts and Contributions/Outcomes
Effects of calcium additions on soil quality need time to be manifested so short term results in two of the fields may not be indicative of the eventual observations. Lime treatments have been in place for 5 years whereas the gypsum treatments have been in place for 3 years (one field) and for only 1½ years (two fields). To date, application of calcium as calcitic lime or gypsum has had limited effects on soil quality in the study fields. Lime application has resulted in a slight increase in soybean yield, but the yield increase has not been large enough to cover the cost of lime in less than 4 or 5 years. Effect of lime on corn yield has been mixed. Gypsum application has had no effect on soybean or corn yield, so benefit will need to be in terms of improved soil quality. At this point in this study, application of lime and gypsum to improve soil quality and crop yield appears to be a marginal practice. The impact of this project may be to show that investment in lime, except for pH adjustment, or gypsum for the soils in the study area of Michigan is not necessary.