- Soil erosion research in the fields of agronomy, soils science
and mechanics, agricultural engineering, hydrology, climatology, and
other scientific disciplines has economic dimensions. In general,
measurable and, at times, significant economic effects are
associated with the effects of erosion in the other disciplines.
Interactions between climate, soils, hydrology, and tillage
practices are incorporated into a stochastic simulation model that
considers twenty six combinations of five tillage systems, three
initial soil depths, two soil associations, two slope classes, and
two annual precipitation levels over one hundred years. The model
endogeneously determines stochastic annual soil loss. Yield is a
function of varying soil depth and technological advance. The model
maximizes the wheat producer's objective, 100-year discounted quasi-rents
from wheat production. Cumulative or total rent distributions
that derive from alternative tillage systems in the different
ecological circumstances are compared under stochastic dominance. In low rainfall, shallow soil areas, annual tillage systems were
preferred to fallow ones, while conservation tillage dominated plow
tillage. In high rainfall areas, for either shallow or deep soil,
conservation tillage dominated plow tillage, while plow tillage
Manipulation of the tillage-associated rent distributions
permitted the estimation of value-of-marginal product or willingness
to pay curves (ordinary, profit-maximizing, input demand curves)
that express the depth of soil as a function of its economic worth.
Properties of these curves are discussed.
Comparison of expected total returns and marginal returns to
topsoil increments under alternative tillage systems in defined
ecological circumstances paralleled the stochastic dominance
results. Rankings of tillage systems by expected total returns
differed between ecological areas and differed from rankings by
Regardless of tillage system or ecological circumstances, the
economic worth of each added soil increment diminished.
The experiment showed that differential rates of soil loss
associated with different tillage systems influence the decision to
continue using or to initially invest in alternative tillages, and
also influence the economically rational wheat producer's
willingness to incur costs associated with soil conservation.
Total and marginal rents associated with single tillages were
found to vary greatly across ecological circumstances. The ability and the willingness to invest in soil conservation were somewhat
divorced. This result has significance for soil conservation