|
TITLE: | Estimating the need for agricultural
liming material |
|
INVESTIGATORS: | J. R. Brown (PI) and John
Stecker |
|
OBJECTIVES: | Complete a position paper on the
status of liming material recommendations in Missouri. |
|
| Make suggestions for further research and
changes in Missouri liming practices based upon an extensive review
of research on soil acidity in Missouri soils. |
|
METHODS: | Publications starting in 1904 authored
by faculty and students were reviewed relative to liming acid
Missouri soils. Notes were taken to illustrate the development of
recommended liming practices in the state through 1969. |
|
| Following a compilation of research
results by T. R. Fisher in 1969 significant changes had been made in
both the quick soil tests used to identify soils needing lime and in
the recommendations. The bases of these changes were worked out and
summarized in one section of the new document. |
|
| Several projects were still underway when
Fisher compiled his 1969 summary and the publications from these
studies were reviewed and summarized for the current document.
Since 1970 several graduate students in the soil science program
have completed advanced degrees using some aspect of soil acidity as
a research topic. The resulting theses in some cases have not been
published. Each of the theses was reviewed and summaries are
included the manuscript. |
|
| The final activity, to be completed, is to
evaluate the current liming material recommendations and suggest
revisions based upon the material reviewed for the paper. The
result will be submitted to the Soil Fertility Work Group for review
and necessary action. |
|
FINDINGS: | The document is incomplete as yet.
There have been numerous laboratory and greenhouse studies show that
soils with active aluminum, which is found in soils below pHs 4.8,
do not reach the target level of acidity when lime recommendations
are followed. Such soils are dominantly in the Ozark region of the
state where Untisols or very acid Alfisols dominate the landscape.
Greenhouse work as well as 1 field study indicated that this may not
be a yield limiting problem but causes producer concerns about the
inadequacy of the liming program. The reason for the failure to
reach the target range is due to labile Al that is very slowly
neutralized with the liming material. The current quick test for
estimating liming needs does not measure this labile
aluminum. |
|
| Attempts were made to find a soil test
that would measure the labile aluminum. Two techniques demonstrate
possibilities. An extraction of Al with 0.33M LaCl2 and adding
liming material equivalent to twice that M KCl exchangeable aluminum
showed promise in greenhouse studies. Both of these techniques will
require field-testing. |
|
| The Missouri Soil Test Laboratory data
file was used to evaluate the relationships between soil pHs,
neutralizable acidity and percentage base saturation. These results
were evaluated against the data used to develop current
recommendations. There were few differences when the mid-range of
soil CEC (12-16 me/100g) was compared across the two data sets.
There was evidence that inclusion of the CEC into lime
recommendations might improve precision but such action may be
academic when one considers the imprecision of spreading quarry-run
limestone. The needs for greater precision in site-specific crop
management may provide incentive for use of finer grinds of
limestone and more frequent applications with better spreading
equipment and/or more accurate placement in the soil. Again, field
evaluation is needed. |
