Effects of limed manure digestate application in sandy soil on plant nitrogen availability and soil N2O emissions

Abstract

Anaerobically-digested manure is frequently applied to agricultural soil to enhance plant growth and reduce the need for chemical fertilizers. This practice also stimulates microbial nitrogen transformations and often results in N₂O emissions. A single mesophilic anaerobic digestion is insufficient for pathogen removal or inactivation and therefore, a post treatment is required for its stabilization and hygienization. Here, we examined the effects of limed manure-digestate as a nitrogen source for plant growth and on N₂O emission compared with compost. A plant growth experiment was conducted in a sandy soil and N₂O emissions were monitored throughout the experiment. Plants were irrigated with freshwater or liquid-N fertilizer. The combination of compost application and liquid-N fertilizer resulted in surface N₂O fluxes over 0.7 ​mg ​m⁻² d⁻¹, which were correlated with ammonium concentration in the soil. The presence of N₂O in the rhizosphere was only detected in compost-amended soil 2–10 days after plantation. A significantly-lower surface N₂O flux of 0.4 ​mg ​m⁻² d⁻¹ was recorded with application of limed-digestate, probably due to its effects on nitrogen-transforming microorganisms. Both compost and limed-digestate enhanced plant growth, with a more distinct effect in the freshwater treatment. Our observations demonstrate that limed-digestate can be an efficient substitute for compost as it effectively supports plant growth with substantially-lower N₂O emissions.