I was 900 producers from which we obtained over 630 useable responses. The sample size for Phase II was 310 producers randomly selected from the subset of producers who were part of the Phase I efforts. The data collection for Phase II was conducted in the winter and spring of 1998, followed by data entry, edit checks, and compilation of summary statistics. The first phase of the farm-level model component of the project was conducted using data collected for Montana dryland grain farms. An econometric production model was estimated and used to construct a prototype simulation model which represents farmers' land use and management decisions on a spatially explicit basis.
Spatial variation is introduced into the model in two ways.
First, differences in yields and cost of production are captured by the spatial dummy variables in the econometric model. Second, the climate-induced changes in yields are input into the simulation model to shift the mean productivity of the crops. We developed a protocol for linking this model to yield data generated by the Century model, and for linking the economic model's outputs to Century. The results of the simulation model show that there is considerable spatial variation in the yields, costs and returns by crop and the type of rotation and tillage system used. These differences in rotation and tillage in turn impact sequestration of carbon in the soil.