Unveiling the effects of construction measures and heat emissions from underground power cables on maize growth and yield

Abstract

The impact of underground energy transmission lines on agricultural crop productivity is primarily unknown. Under Germany's Renewable Energy Sources Act, the grid expansion will be conducted underground through arable land. Construction measures through trenching and resulting heat dissipation using 525 kV high voltage direct current (HVDC) might affect soil properties and crop growth. A 2-yr field study was conducted as an on-farm field trial on an Abruptic Luvisol with the dominant texture of Loam in Southwestern Germany from 2021 to 2022. The intricate dynamics between trench construction measures, backfilling methods, and heating pipes on silage maize (Zea mays l.) growth and yield were analyzed in five treatments: 1) heated trench (HT) with conventional backfilling (CONV), 2) HT with alternative backfilling (ALT), 3) unheated trench (UT) with CONV, and 4) UT with ALT and 5) Control. In the ALT subsoil backfilling, the soil was pressed with an excavator bucket and compacted to 90 % of the bulk density of the natural soil. In contrast, in the CONV subsoil backfilling, a trench roller was used to press to 95–100 % of the bulk density of the natural soil. Trenching and heating treatments impacted the surrounding soil and changed the initial soil conditions, leading to significant differences in soil properties like bulk density, soil water content, and temperature. Due to varied amounts of rainfall, 481 mm in 2021 and 209 mm in 2022, a seasonal effect on maize growth and yield was observed for the Control, resulting in a total above-ground biomass of 31.2 ha⁻¹ in 2021 and 9.8 t ha⁻¹ in 2022. The favorable growing conditions in 2021 led to no significant changes in maize growth or yield across the treatments. When subjected to water-limiting conditions and heat stress in 2022, notable differences in yield, particularly during the crucial grain-filling stage, were detected. Soil backfilling method and soil heating significantly affected total above-ground biomass at harvest, resulting in a 49 % increase for the HT-ALT treatment and a 13 % yield loss for the UT-CONV treatment compared to the Control. Overall, construction activities and heat emissions from heated pipes affected maize growth and yield in the first two years, and with the differentiation of construction methods, the ALT backfilling method showed promising results in minimizing potential disruptions in agricultural productivity.