Precision Agriculture, 2, 55᎐70, 2000
ᮊ 2000 Kluwer Academic Publishers. Manufactured in The Netherlands.
Economics of Variable Rate Lime in Indiana
National Institute for Agricultural Technology INTA , Manfredi, Cordoba, Argentina
Department of Agricultural Economics, Purdue Uni
ersity, West Lafayette, Indiana
Abstract. In Indiana, variable rate application VRA of lime is often considered a good place to start
site-specific management SSM . This is because soil pH is one of the most variable of manageable soil
characteristics in the state, the availability of essential nutrients is closely related to soil pH, and
because spreaders can be retrofitted relatively inexpensively to do VRA. The objective of this study is to
evaluate the profitability of VRA for lime as a stand-alone activity. The methodology involves a
spreadsheet model using corn and soybean pH response functions estimated with small plot data. The
overall results indicate increased annual returns to corn and soybean production with site-specific pH
management strategies. On average, SSM with agronomic recommendations provides an increased
annual return of $7.24 per hectare ha q1.78% . SSM with the economic decision rule provides an
average increase in annual return of $19.55 ha q4.82% . Information strategy, which uses site-specific
information to determine the economically optimal uniform rate of lime, provides an average increase
in annual return of $14.38 ha q3.54% .
Keywords: site-specific management, variable rate, lime, profitability, economic analysis
Soil acidity and liming
Soil acidity is commonly indicated by soil pH, a measure of hydronium ion activity
in a soil suspension. Acidity may be created by a removal of bases by harvested
crops, leaching, and an acid residual that is left in the soil from nitrogen fertilizers,
and it has long been recognized as one reason soils become unproductive. Liming
to correct soil acidity has been practiced for centuries, but during the last several
years, limestone use has tended to decrease while crop yield and nitrogen fertilizer
use have increased markedly Frank, 1994 .
Soil variability within farm fields has long been recognized by soil scientists as
well as farmers, and soil pH is one of the soil characteristics with the highest
spatial variability Cline, 1944 . Lime used to correct pH is an important cost for
Indiana farmers. The per unit cost is low relative to other fertilizers, but the
application rates are comparatively high. Lime application is measured in tons,
Ž. Ž. Ž. Ž.
instead of the kilograms kg used for nitrogen N , phosphorus P and potash K .
Uniform rates can leave underlimed areas or apply lime to portions of the field
where the soil pH is satisfactory. Unlike some other fertilizers, lime can produce a
negative effect on crop response if it is applied in excess. Most crops require some