Effects of Sugarbeet Residues on Soil Redox Potential and Nitrous Oxide Emission

Abstract

AbstractThe influence of the incorporation of fresh sugarbeet (Beta vulgaris L.) plant residues (green weight, 36.5 t ha−1; N content, 113 kg ha−1) on microbial activity, soil redox potential, and N2O emissions was studied using soil microcosms with an automated registration of N2O and CO2 emissions. The experiment was conducted in well‐drained soil columns (water‐filled pore space 63%) and in soil columns with temporary water‐logging (water‐filled pore space continuously increased to 81‐89% for 5 to 7 d). The cumulative CO2 losses during 45 d were equal for the well‐drained and the temporarily water‐logged soils and amounted to ≈30% of the total residue C added. For the well drained soils, the total N2O‐N emission during 45 d was 35‐fold higher than for the control without added plant residues and amounted to 0.37% of the residue‐bound N. Water logging increased the N2O‐N losses to ≈1% of the N added with the sugarbeet residues. The period of increasing N2O release coincided with the starting net mineralization of the residue N and decreasing redox potentials in the vicinity of the plant material. The greater availability of NO−3 combined with enhanced metabolic activity led to the formation of anaerobic microenvironments within and around the plant residues, providing favorable conditions for denitrification. The results emphasize the importance of anoxic zones in the soil caused by respiratory O2 consumption for N2O production in well‐aerated soils and indicate that N2O emission from N‐rich plant residues could be in the same order of magnitude as reported for mineral N fertilizers.