Non-inversion tillage benefits soil N retention during bare soil period coinciding with wet spell

Abstract. Recent meta-analyses suggest risks of increased nitrate leaching with the implementation of reduced tillage practices. This study aimed to quantify effects of a subsidized and commonly implemented form of non-inversion tillage in Switzerland (NIT, i.e. chisel ploughing) in comparison to conventional tillage (CT, i.e. mouldboard ploughing) on nitrate leaching and its driving processes (i.e. water fluxes, soil temperature, plant uptake). A lysimeter experiment was conducted at the lysimeter facility Reckenholz/Zurich in Switzerland, mimicking tillage differences. Results after three years of treatment implementation show that during the following three years, cumulative nitrate leaching was 26 % higher under CT than under NIT (i.e. 63 ± 10 kg/ha N with CT vs. 46 ± 9 kg/ha N with NIT). The observed effect was driven by differences in nitrate concentrations in seepage water rather than seepage water amounts. The beneficial effect of NIT on nitrate leaching was most pronounced during and shortly after a bare soil period following sugar beet cultivation, which coincided with above-average spring precipitation. These findings suggest that reduced soil management may hold the potential to reduce nitrate leaching during winter and spring wet spells with poor plant cover, which are expected to become more frequent with progressing climate change.