SPACE-TIME UPSCALING OF PLOT-BASED RESEARCH INFORMATION - FROST TILLAGE

Most agronomic-environmental research information is based on plot-sca le studies conducted for a limited time period, typically two to five years. Generalization is required for larger spatial domains, typicall y a farm, watershed, or region, and more representative climate period s, at least thirty years. Frost tillage research was conducted at the plot scale at one primary and two ancillary sites. Results indicated t hat this tillage method is viable and the processes leading to frost-t illable soil conditions are minimally affected by variation of soil pr operties. The estimation of seasonal probabilities for frost-tillage c onditions was determined to be an assessment need for the adoption of the practice. A soil freezing model using basic climate information on minimum and maximum air temperature and snow depth from a dense netwo rk was developed and calibrated for sod and bare soil surfaces based o n measured soil temperature data from 8 weather station-years. It was independently validated based on data from frost depth tubes. Observed and predicted frost-tillable days for cropped fields were compared an d showed good agreement when averaged for bare and sod surface conditi ons. Soil freezing was simulated for 275 observation sites in the Nort heastern USA based on 40-year climate data. Frost tillable days were d etermined and mapped as the annual number of days in which it can be p erformed at various recurrence periods. Upscaling methodology used in this study is discussed, especially as it relates to the identificatio n of relevant processes and their stochastic nature.