ABSTRACTThis paper reviews the data and models used to simulate the field drying of grass in swaths. The main factors influencing the drying rate are solar radiation, vapor pressure, rain, the swath structure and the thin layer drying rate of the grass. Most models consider these factors to some extent. The simulation of swath drying is well developed, with some models considering the heat and mass transfer processes in the swath. But the modelling of swath structure and the effect of rain have received less attention. The models agree on the effect, on the drying rate, of all weather factors except wind speed. Some models predict that more wind is beneficial, others say the opposite. This problem has not been resolved experimentally.