Conrad P. Lyford

A Test for Choice between Hyperbolic and Sigmoidal Models of Crop Yield Response to Weed Density

The form of a crop yield-weed density response function influences control thresholds and risk management strategies. A choice of model test is introduced for evaluating whether yield response to weed density is sigmoidal or hyperbolic. A null hypothesis of hyperbolic yield response is evaluated in a Monte Carlo simulation of sigmoidal yield functions. The analysis considers two probability distributions of weed density and varying degrees of functional curvature, data variability, and sample size. The results suggest that, given empirical levels of functional curvature and data variability, sample sizes larger than the norm in weed science are required to reject the null hypothesis of hyperbolic response.

The market valuation of the FGIS grain quality characteristics

The issue addressed in this paper is whether the grain quality factors used by the Federal Grain Inspection Service in determining the quality grades of wheat exported by the United States including test weight, dockage, moisture content, percentage of foreign material, percentage of shrunken and broken kernels, and protein content are characteristics that influence the price of wheat for export. Using shiplot data on the transactions price for hard red winter wheat, hard red spring wheat and soft white wheat and the associated quality characteristics covering the period January 1990 to October 1991 and exported to 63 countires, the results suggest that only the test weight and the protein content are characteristics consistently valued by the market.

The Effect of Quality on Corn Export Price Determination

This article examines export price formation for U.S. corn exports, adopting the hedonic approach of treating a commodity as a bundle of identifiable quality attributes for which separate implicit prices can be estimated. The study makes use of a rich data set which includes transaction-level price and quality data for U.S. corn exports for a period of two years. Significant implicit valuations for key quality factors between corn importers for feed use and corn importers for food and industrial uses are found, suggesting that the different end-uses substantially affect how users contract for corn imports.

The market valuation of soybean quality characteristics

Abstract The price and quality characteristics of 213 shiploads of US soybeans exported between January 1990 and October 1991 are examined using hedonic analysis. The results of the analysis confirm that the price of soybeans exported is determined in part by the protein and oil content of the soybeans. The analysis further reveals the effects of country‐specific domestic and import strategies on component pricing of soybeans. For example, in Japan and The Netherlands, the two largest import destinations for US exported soybeans, the value of both soybean oil and soybean meal have positive effects on the price of soybeans. For the Republic of Korea, however, the soybean meal content does not affect the price of soybeans imported from the US. Measures of the processable content of soybeans such as damaged kernels and the percentage of foreign material, as expected, have statistically significant negative effects on the export price of soybeans, although not in all markets. Finally, the US grades and standa...