This study utilizes a dynamic programming decision model, considering an intertemporal nitrogen carryover function, combined with both linear stochastic and deterministic plateau response functions to evaluate optimal nitrogen fertilizer decision rules and net present values (NPVs) in Texas High Plains cotton production. Nitrogen recommendations and NPVs are influenced by response function choice and nitrogen-to-cotton price ratios. Results indicate the stochastic plateau function better describes the data; the optimum nitrogen recommendation is to apply approximately 40 lb. of nitrogen for each bale of cotton production when considering nitrogen carryover information.

The question of the optimal nutrient application in agricultural production continues to gather attention because of its relevance in increasing the profitability of crop production and protecting the environment. Economically optimal nutrient application decision rules are commonly derived by fitting crop yield functions to nutrients. The choice of the appropriate yield functional form thus is critical for estimating unbiased and more precise nutrient recommendations. This review explores recent developments in yield response functions to the nutrient application. We first introduce the concept of the economic theory of production and yield response functions. We then explain, with mathematical equations, some commonly used functional forms: quadratic response, Mitscherlich-Baule, deterministic, and stochastic plateau functions. We also summarize the strengths and weaknesses of each functional form and its implications for nutrient management strategies from an economic perspective. In recent studies, researchers have suggested that stochastic plateau functional forms, both linear and quadratic, could explain yield response to the nutrient application in a better way. Finally, we recommend fitting stochastic plateau functions in conjunction with carryover information in a dynamic optimization setting may yield more accurate optimal nutrient levels. Future research should continue to investigate whether these functional forms perform better in different crop and soil environments.

A nutritional transition is occurring in Sri Lanka, which steers people away from nutrient-rich diets, contributing to diet-related disease and poor economic performance. This study examines demographic impacts on consumption of major food commodities and estimates price and expenditure elasticities for major food groups and nutrients. Data from the Sri Lankan Department of Census and Statistics Household Income and Expenditure survey are used to estimate price and expenditure elasticities for food commodities and nutrients using the Quadratic Almost Ideal Demand System (QUAIDS). The zero-expenditure problem is circumvented by employing a Tobit model. Results demonstrate the impact of price and income changes on dietary intake of households, and income and nutrition policy recommendations are presented.

E-commerce has emerged as a viable option for connecting agribusinesses and consumers within the food marketing system. The purpose of this review is to assess the current status and impact of e-commerce in the food marketing system. The review comprises issues related to adoption and use of computers and the internet by agribusinesses and the economic impact of e-commerce for these businesses. The review also covers aspects related to the importance of consumers' e-commerce food purchases, the factors affecting its usage and some new developments in the use of e-commerce to market food products using social media and mobile marketing. Regarding the adoption and use of e-commerce by agribusinesses, we find heterogeneous rates of adoption, use and impact across sectors and countries. For example, in the USA even though 67% of farms had access to the internet in 2013, only 14% reported conducting marketing activities over the internet. On the other hand, US Census data show that in 2012 the e-commerce value of food product manufacturing shipments accounted for more than 50% of their total value. Data from the USA and UK, two of the most advanced e-commerce markets in the world, indicate that food internet sales account for less than 4% of total sales. We conclude that while e-commerce has influenced the food marketing system, its impact does not appear to have been as dramatic and swift as had been expected. More research is needed in order to better understand the ways in which e-commerce affects agribusinesses and consumers. The review also identifies a paucity of e-commerce related statistical data.

No abstract