SIMULATION OF THE GROWTH RESPONSE OF DRYLAND AND IRRIGATED CORN*

This paper studies the complex relationship between plant growth and the variables affecting that growth. The author has developed several growth models, with soil moisture being a primary explanatory variable in the models. The relationship of plant growth to moisture is demonstrated by the sensitivity of a corn plant to moisture at different periods in its growth. Ce papier fail une études des relations complexes entre la croissance des plantes et les variables qui influent cette croissance. ?auteur a construit plusieurs modèles de croissance en se servant de ?humidité du sol comme variable primaire explicalif La connexité entre la croissance des plantes el ?humidilé est démonstée en utilisant une plante de blé d;inde ei en montrant comment sensible à?humidité est cette plante à differentes étapes de sa maturation.     

Agricultural Supply Response: A Survey

This paper surveys the literature on agricultural supply response to prices in developing countries. Empirical estimates of elasticities depend both on the methodology adopted and on country-specific factors relating to technology, economic structure and macro constraints. The paper seeks to establish some general conclusions on supply responsiveness within these limitations. Supply response to output prices at the aggregate and at the crop levels is considered first. Crop-specific acreage elasticities range between zero and 0.8 in the short run while long-run elasticities tend to be higher — between 0.3 and 1.2. Yield elasticities are smaller and less stable than acreage elasticities. Clearly, inter-crop pricing can be relied upon to effect shifts in the commodity composition of agricultural output. Evidence also suggests that supply elasticities vary systematically with such factors as price and yield risks, multiple-cropping, the importance of the crop, farm incomes, farm size, tenancy and literacy. The most controversial and important aspect of supply response is the effect on aggregate agricultural output of agriculture's terms of trade. Conventional time-series estimates range from 0.1 to 0.3. A major cross-country study reports an aggregate elasticity as high as 1.66. It is argued that cross-country estimates are apt to exaggerate aggregate responsiveness while time-series studies underestimate it somewhat. For LDCs, a tentative range of 0.4 to 0.5 seems plausible. Hence, the distributive effects of the terms of trade are likely to be more significant than the allocative effects. Asian evidence shows that only a third of the inter-country differences in fertilizer use can be attributed to fertilizer price policies. Provided new technologies and infrastructure are in place, fertilizer subsidies can help in technology diffusion and in overcoming credit constraints. The choice between price supports and input subsidies will depend on a variety of country- or situation-specific factors. Nevertheless, a significant general factor favoring price supports is that they can more easily be coupled with price stabilization goals than input subsidies. Though sparse, the available evidence on the response of marketed surplus suggests that price policy is not a reliable instrument for regulating inter-sectoral trade.     

Why Farmers Quit: A County-Level Analysis

We identify the effects of alternative explanatory variables on the propensity of U.S. farmers to cease farming, with a particular emphasis on understanding the roles of off-farm employment and federal farm program payments. Conventional ordinary least squares analysis using all counties suggests that off-farm employment has no statistical effect on the (net) number of farmers quitting between 1987 and 1997, ceteris paribus . A more refined analysis, which separates counties losing farmers from those that gained farmers, reveals subtle and less clear-cut effects of off-farm employment (and federal program payments) on farm exits.     

The Rural Environment Protection Scheme of the Republic of Ireland

Agricultural modernisation has had an impact on the Irish environment but official policy to address this developed only slowly. The reform of the EU CAP provided the incentive for the formulation of the Rural Environment Protection Scheme (REPS). This is a wide-ranging scheme to promote environmentally friendly farming through application of 11 measures and six supplementary measures. Significant characteristics of the REPS include its: universal availability, voluntary nature, comprehensiveness, payment limitation, tailoring to individual farms and inclusion of training. There has been a high level of adoption, with participation being greatest in the small-farm west with its cattle and sheep enterprises.     

The Economics of Erosion and Sediment Control in Southwestern Ontario

This paper compares the costs of off-farm damage from sediment displaced through erosion from southern Ontario cropland with the costs of erosion control to farmers using available conservation tillage techniques. The SOILEC model is used to simulate the long-run on-farm profitability of alternative tillage systems. The Guelph model for evaluating the effects of Agricultural Management systems on Erosion and Sedimentation (GAMES) is used to estimate changes in sediment delivery rates under different production systems. The results of the analysis indicate that the off-farm gains from the use of conservation tillage generally exceed the on-farm costs of erosion control for southwestern Ontario growing conditions. Le présent document compare les coûts des dommages causés à l'extérieur des régions agricoles par le déplacement des sédiments sous l'effet de l'érosion des terres agricoles du sud de l'Ontario aux coûts des techiques de conservation du sol devant être utilisées par les agriculteurs pour lutter contre l'érosion. Le modèle SOILEC est utilisé pour simuler la rentabilitéà long terme, pour les agriculteurs, d'autres techniques de travail du sol. Le modèle Guelph pour évaluer les effets des systèmes de gestion agricole sur l'érosion et la sédimentation (GAMES) a également été utilisé pour estimer la variation du taux d'écoulement des sédiments en fonction de différents systèmes de production. Les résultats de l'analyse indiquent que les gains à l'extérieur de la ferme résultant de l'application de techniques de conservation sont en général supérieurs aux coûts des mesures de lutte contre l'érosion devant être utilisées à la ferme, dans les conditions de culture s'appliquant au sudouest de l'Ontario.     

CONGESTION MODELS WITH CONSISTENT CONJECTURES

This paper demonstrates that, in situations in which a cumulative externality exists, the basic nature and extent of resource misallocation may be substantially less than we imagine. This conclusion stems from deriving consistent conjectures in a unified framework in which congestion is present. Experiments support the conclusion that, when numbers of agents are small, when there is little heterogeneity among them, and when they have the opportunity to observe each other during repeated experiment, the market allocation may be efficient.