Soil organic carbon stocks in sugar beet rotations differing in residue management and associated rotational crop species

Abstract

AbstractBackgroundCrop rotations with sugar beet (SB) vary in accompanying crops, affecting the organic matter input into the soil and thus the soil organic carbon (SOC) stocks. Furthermore, the impact of aboveground SB residues themselves on SOC stocks is unclear.AimsThe aims of this study were to analyze the effects of three SB rotations and different amounts of SB residues on SOC stock development.MethodsIn a field experiment started in 2006, three different SB crop rotations [(1) SB–winter wheat (WW)–WW, (2) SB–WW–silage maize (SM), and (3) SB–WW–winter oilseed rape (WOR)–WW–WW–grain pea (GP)] were sampled for SOC stocks in 0–10, 10–20 and 20–30 cm soil depth in spring of 2018 and 2019. Further plots with an SB–WW–WW rotation received either no or the doubled amount of aboveground SB residues and were sampled as described above.ResultsAfter four rotations, doubled SB residues led to significantly higher SOC stocks in 0–10 cm depth compared to the removal of SB residues. However, the effect was relatively low with 12% of the added residue‐C being recovered in the soil. Comparing different SB crop rotations, SOC stocks in 0–20 cm depth were significantly higher in the SB–WW–WW compared to the SB–WW–SM rotation, while the SB–WW–WOR–WW–WW–WW–GP rotation was intermediate. Differences in SOC stocks were likely due to the different amounts and possibly quality of crop residue C input.ConclusionIn total, the accompanying crops rather than the share of SB seem to be decisive for SOC development in SB rotations.