Improving nitrogen retention of cattle slurry with oxidized biochar: An incubation study with three different soils

Abstract

The application of livestock slurry in soils can lead to nitrogen (N) losses through ammonia (NH3) emission or nitrate (NO3−) leaching. Oxidized biochar has great potential to mitigate N losses due to its strong adsorption capacity; however, the effects of oxidized biochar in different soils treated with slurry are currently unclear. Here, we investigated the effect of untreated and oxidized biochar (applied at a rate of 50 kg C m−3 slurry) on reducing N losses in a laboratory experiment with three different soils (loamy sand, sandy loam, loam) amended with cattle slurry at an application rate of 73 kg N ha−1. Oxidized biochar reduced NH3 emissions by 64–75% in all soils, whereas untreated biochar reduced NH3 emissions by 61% only in the loamy sand. Oxidized biochar significantly reduced the NO3− content in the soil solution of the loamy sand in the early phase of the incubation and led to a significantly higher NO3− concentration in the same soil compared with the slurry‐only treatment at the end of the experiment, indicating a significant increase in NO3− retention in this organic C–poor soil. We conclude that oxidized biochar can reduce N losses, both in the form of NH3 emission and NO3− leaching, from cattle slurry applied to soil, particularly in soil with soil organic carbon content <1% and pH <5 (i.e., oxidized biochar can serve as a means for improving the quality of marginal and acidic soils).