Glenn Fox

Abstract The economic feasibility of three different fertilizer management strategies (constant rate, three‐rate and multiple‐rate technology) in the application of nitrogen fertilizer to corn are compared under different probability distributions for field fertility. A constant rate was more profitable than either variable‐rate technology system for homogeneous fields with low fertility. The application area at which the relative profitability between systems changed was largely determined by the characteristics of the fertility distribution rather than by assumptions regarding costs. Variable‐rate technology improves groundwater quality in low‐fertility fields by reducing total fertilizer applied and in high‐fertility fields by increasing corn yield.

Abstract The indirect action of damage control inputs means the marginal productivity of these inputs depends on their effectiveness in controlling the level and size of production loss caused by the damage agent. Increasing returns to damage control inputs can occur even when control and damage functions are concave. The result implies more attention needs to be paid to the functional form selection for damage and control functions in empirical work on pest control and other types of damage control inputs. In addition, the possibility of increasing returns may undermine the general use of taxes to reduce pesticide use.

Abstract That the level of public investment in U.S. agricultural research is too low is widely accepted. This paper argues that there are two important limitations to the evidence assembled in support of the underinvestment hypothesis: ( a ) many authors have compared the social rate of return to public investments with the private rate of return to private investments; ( b ) costs of public expenditures on agricultural research have been underestimated by a failure to account for the marginal excess burden of the tax collection system. Taking these two factors into account, evidence in support of the underinvestment hypothesis is weakened considerably.

Weed control decision rules were derived for the application of postemergence herbicides to control pigweed species in soybean. Field experiments were conducted at two locations in 1992 and 1993 to evaluate soybean-pigweed interference. A damage function was determined that related yield loss to time of pigweed emergence, density, and soybean weed-free yield. A control function described pigweed species response to variable doses of imazethapyr and thifensulfuron. The integration of these two functions formed the basis of an economic model used to derive two weed control decision rules, the biologist's “threshold weed density” and the economist's “optimal dose.” Time of weed emergence had a more significant role than weed density in the economic model. Later-emerging pigweed caused less yield loss and therefore, decision rules lead to overuse of herbicides if emergence time is not considered. The selected herbicide dose influenced the outcome of the control function. Depending on the desired level of weed control, a herbicide could be chosen to either eradicate the escaped weed species (label or biologically-effective doses) or reduce the growth of the weed species and thereby offset interference (optimal dose). The development of a biologically-effective dose by weed species matrix was recommended. Decision rules should not be utilized as an exclusive weed management strategy but rather as a component of an integrated weed management program.