Title : Sub-surface heating of farmland to promote early harvest and increase productivity in northern Sweden
Abstract:
During the last decades, farmers in the North of Sweden have been struggling with declining profits of their produce forcing many family farms into liquidation or closing. As a result, the farmed land area in the North has been shrinking continuously with about 1% each year since the turn of the new millennium and the self-sufficiency for food in the region has dropped from 50% in 2000 to 25% in 2023. One major disadvantage northern farmers face in comparison to their colleagues in the south is the late seed and planting date due to the frozen ground in the beginning of the growing season, and the consequential lower ground temperature over the early part of the summer. The cool ground slows root development, which is vital for the growth rate of the rest of the plant. As a result of this delayed start, crop production per hectare will be lower in the North. But there are also advantages to growing food in the North. For example, the farmland is of very good quality and relatively cheap, and there is generally no lack of irrigation water. The cold winters kill off many of the common pests, which minimizes the need for pesticides. Most importantly however, the region receives more sunlight hours with optimum photosynthesis than most locations in Sweden, which increases the nutrition value and flavour of the crop, especially noticeable in fruits and berries. The aim of this research project is to provide the existing farmers in the North with methods for increasing their profits by adding in some high value crop on the farm. In this field study, waste heat from the farm in the form of warm air is supplied to underground drainage pipes that are buried horizontally at 10-20 cm depth in the planted field. The warm air thaws the frozen ground around the plant roots and supplies heating from below so that planting can be advanced from end of May to middle of April, when the sunlight hours already exceed 16 hours per day. During the initial tests 2025-2026, field-cultivated strawberries are being planted to investigate how the onset of flowering and maturation, and volume and quality of the berries in a heated field compares to a reference field. The ground heating and thawing will commence in March 2025. Future research plans include diversifying the pre-heated research field with crops such as asparagus, artichoke, and grapes for white wine production, which have a higher sell price than conventional produce from the North.
