Soil loss due to crop harvesting in highly mechanized agriculture: A case study of sugar beet harvest in northern Germany

Soil loss due to crop harvesting (SLCH) is a globally occurring and underestimated process that promotes soil degradation. Despite its negative effects on soil functionality and fertility SLCH has received comparatively little scientific attention to date. In Europe, sugar beets hold particular significance due to high production rates, while research in commercial mechanized farming of sugar beets is lacking. The aim of this study is to measure SLCH for sugar beets including nutrient and SOC losses using typical state of the art harvesters and compare that values to estimated SLCH provided by sugar beet factories. In addition, we tried to identify crop and soil variables that influence SLCH. Therefore, sugar beets and soil samples were collected for 14 sampling sites over a three-year period in Northern Germany to measure SLCH dependent on different crop characteristics, soil properties and weather conditions. The results indicate that SLCH is 0.064 kg per kg harvested sugar beet (SLCHspec) on the average, which corresponds to a loss of 5.7 Mg ha-1 harvest-1 (SLCHcrop). These numbers are higher than former comparable studies but also of about 83.3% higher than SLCH estimated by sugar beet factories. Additionally, amounts of SLCH considerably varied between years and fields, but also within fields. The most influential variables on SLCH are soil water content (SWC) and clay content, and we also observed that soil properties impact SLCH differently in relation to SWC. Moreover, we estimated that SLCH of sugar beets can lead to significant SOC and nutrient losses, latter resulting in direct costs for farmers of 18-34.4 <euro> ha-1 harvest-1. The results confirm the importance of considering SLCH for soil degradation analyses and estimations and the need for models which spatially assess SLCH from field to global scales. This is important to explore soil conservation measures and strategies to reduce ongoing soil degradation especially in highly mechanized agriculture.