A logistic growth equation with time and location varying parameters was used to model corn response to applied nitrogen. A nonlinear dummy-variable regression model provided a parsimonious representation of site and time effects on parameter values. The model was used to test for the equality of the mean marginal product of nitrogen fertilizer between locations on the coastal plain of North Carolina. Monte Carlo simulation and bootstrap simulation were used to construct finite sample covariance estimates. Results support rejection of the hypothesis that mean marginal products are equal when nitrogen is applied at 168 kg/ac. A comparison of bootstrapped errors and asymptotic errors suggests that results based on asymptotic theory are fairly reliable in this case.

The purpose of this study was to examine the impact of situation and outlook information from World Agricultural Supply and Demand Estimates (WASDE) in corn and soybean futures markets over the period 1985 to 2006. Results indicate that WASDE reports containing National Agricultural Statistics Service (NASS) crop production estimates and other domestic and international situation and outlook information have the largest impact; causing return variance on report sessions to be 7.38 times greater than normal return variance in corn futures and 6.87 times greater than normal return variance in soybean futures. WASDE reports limited to international situation information and domestic and international outlook information have a smaller impact. The results show that the impact of WASDE reports has increased over time.

This paper describes the programming required for online homework, evaluates its use, and presents methods for student identification and for processing student input. Online homework applications were evaluated in a real class setting. Generally, online homework is cost effective for large classes that have numerous assignments and repeated usage. Online homework appears to increase learning through increased student study-time allocations. Students felt that online homework made course website interaction more productive. They also indicated that online homework increased their perception of the value of lectures and that its use in other courses would be welcome. All findings were highly statistically significant.