The boiling properties are an important quality issue of the potato. In order to obtain adequate boiling properties the growth of the potato needs to be controlled and interrupted at the right time. However, it is difficult to determine when to stop the growth. Specific gravity can easily be measured and can sometimes be used as a tool for estimating the boiling properties.
This report discusses different aspects of the specific gravity of the potato and how it can be used as a tool to determine the appropriate time for vine killing. The study includes a literature study and a practical field trial. The field trial has been conducted on five different farms situated in the southern parts of Sweden and includes three different varieties. Two sites were selected at each field along with the farmers, one site with low field capacity representing the dry site and one with higher field capacity, representing the wet site. The aim of this study was to get a better understanding of how the specific gravity can vary within the field, but also to evaluate the potato hydrometer as a tool for finding the right time to stop the growth of the potato crop.
Water is the most important factor influencing the growth of most plants. Both water and nutrient supply will affect the boiling properties and specific gravity of potatoes. Potato is a crop that requires a good access to water and nutrient. Nitrogen is the nutrient that has the greatest impact on the specific gravity, quality and yield of potato crop. The specific gravity is closely liked to the maturation of the potato plant.
The results from this study show that there can be great differences in boiling properties within a field. However, sometimes fields that vary in quality and yield can have a uniform development of the specific gravity. It seems like different varieties has different tendencies to develop a uniform specific gravity. King-Edward is a variety which tends to have relatively uneven specific gravity within the field, while the specific gravity in Bintje and Fakse seems less influenced on external factors such as une...
