An operational forecast model for soil temperature in plastic-covered asparagus production systems.
In Germany, asparagus is usually grown in soil ridges covered by different kinds of plastic. The major objective is the stretching of the harvest season, with a combined use of early cultivars and warming plastic cover types and the use late-sprouting cultivars together with cooling plastics. Secondary objectives are a good quality of spears and short-term control of asparagus yield. Meanwhile, several cover types are used, which consist of one to three layers of plastic. Depending on the current objectives of the grower, he has to choose one cover type. Currently, this decision is based largely on soil temperature, which is measured on farm or provided by central monitoring services over the internet. But cover management would be sounder if the grower knew future soil temperatures in advance below the most important covers. Therefore, we developed a physical model that is able to predict soil temperature below black and white plastics, and mini‐tunnels covering black plastics. New solutions were derived for an approximated 2D soil heat transfer, the radiation exchange between the covers and convective heat exchange between the mini‐tunnel and the lower plastic. A 5-year validation period showed even better performance than a previously developed more complex model, which was based on 2DSOIL. The proposed model only requires hourly weather data, optical properties of each plastic layer and basic soil properties such as contents of sand, clay and humus. The developed simulation model is currently operational for six sites located in three German Federal States, Brandenburg, Rhineland‐Palatinate and Bavaria.
Graefe, J. 2017. An operational forecast model for soil temperature in plastic-covered asparagus production systems. Acta Horticulturae 1154, 121-128.