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.