Simulation of Soil Heating in Ridges partly covered with Plastic Mulch, Part II: Model Calibration and Validation

This work presents the calibration and validation procedure of a simulation model to predict the temperature dynamics for soil ridges partly covered by a plastic mulch. To this end, soil temperatures were measured hourly over 3 months at two sites for six different plastic-mulch treatments. For calibration, only three parameters had to be estimated from data taken over one month at one site. Overall, simulated data fitted with the whole data set on soil temperatures, with root mean square errors of 1·5 and 1·9 K for both sites, respectively; thus confirming the validity of this approach. Test simulations established that for opaque plastics, detailed analysis of directional radiative properties is not necessary, and for transparent plastics, rather simpler approaches, such as the Schlick equation, are sufficient. Small-scale advection effects along single ridges were evident, and hourly deviations contributing to this effect reached up to 3 K. Only a few inputs have to be provided to apply the model: the soil humus content and texture, the shape of the ridge, and the transmissivities and reflectivities of the used plastic mulches. The presented model can be applied for optimisations regarding (1) the timing of ridging and covering, (2) the dimensions and orientations of ridges, and (3) the radiative properties of plastic mulches.