Impact of construction measures and heat emissions from the operation of underground power cables on spelt (Triticum spelta L.) growth and yield

Abstract

Germany decided to promote the energy supply toward low or zero-carbon sources by the middle of the century. Therefore, massive infrastructural investments in grid expansion are needed. These grid expansions will be conducted with 525 kV High-Voltage Direct Current (HVDC) cables, buried at a depth of 1.5 m, passing mainly through arable land. The expected main effects of these cables on soils and crops are caused by construction measures (soil excavation and backfilling of soil material) and soil warming caused by heat dissipation using HVDC. To date, the impact of subsoil warming on crop growth and yield has not been studied in detail. This study investigates the effects of construction measures and subsoil warming on a field scale level for a 2-yr data set (2022 and 2023) in South Germany. The intricate dynamics between construction measures and subsoil heating on spelt (Triticum spelta L.) growth and yield were analyzed in three treatments: 1) Heated Trench (HT), 2) Unheated Trench (UT), and 3) Control. Construction measures were conducted by excavating the soil with a triple lift method (separated into three layers: A-, B-, and C-layer), storing them separately in ground heaps, and backfilling according to their natural layering. The triple lift method resulted in a 12.1 % decrease in bulk density (BD) for UT and 8.9 % for HT in the subsoil compared to the Control. The changes in soil properties affected spelt growth and yield, resulting in a yield increase of 14 % for the UT treatment. Additional subsoil warming in the HT treatment increased the topsoil temperature by 1.2 °C and spelt yield by 24 %. The triple lift method showed promising results, minimizing the impacts on soil compaction and maintaining the spelt growth and yield level.