The effect of renovation of long-term temperate grassland on N2O emissions and N leaching from contrasting soils

Abstract

Renovation of long-term grassland is associated with a peak in soil organic N mineralisation which, coupled with diminished plant N uptake can lead to large gaseous and leaching N losses. This study reports on the effect of ploughing and subsequent N fertilisation on the N2O emissions and DON/ NO3 -leaching, and evaluates the impact of ploughing technique on the magnitude and profile of N losses. This study was carried out on isolated grassland lysimeters of three Irish soils representing contrasting drainage properties (well-drained Clonakilty, moderately-drained Elton and poorly-drained Rathangan). Lysimeters were manually ploughed simulating conventional (CT) and minimum tillage (MT) as two treatments. Renovation of grassland increased N2O flux to a maximum of 0.9 kg N2O-N ha -1 from poorly-drained soil over four days after treatment. Although there was no difference between CT and MT in the post-ploughing period, the treatment influenced subsequent N2O after fertiliser applications. Fertilisation remained the major driver of N losses therefore reducing fertilisation rate post planting to account for N mineralised through grassland renovation could reduce the losses in medium to longer term. Leaching was a significant loss pathway, with the cumulative drainage volume and N leached highly influenced by soil type.Overall, the total N losses (N2O + N leached) were lowest from poorly and moderately draining soil and highest for the well draining soil, reflecting the dominance of leaching on total N losses and the paramount importance of soil properties.

Land use intensity, rather than plant species richness, affects the leaching risk of multiple nutrients from permanent grasslands

“…Intensive grassland management is also associated with recurring sward renewal by reseeding after breaking up the old sward. Despite the detection of significant environmental problems caused by losses of N in multiple pathways (Buchen et al., ; Kayser, Seidel, Müller, & Isselstein, ; Velthof et al., ; Whitmore, Bradbury, & Johnson, ), a broad and well‐replicated assessment of multiple soil nutrients in response to sward destruction is still lacking, limiting our knowledge on environmental effects of intensive grassland management on nutrient dynamics (Krol et al., ).…”

Effect of the application of cattle urine with or without the nitrification inhibitor DCD, and dung on greenhouse gas emissions from a UK grassland soil

“…The occurrence of multiple N 2 O peaks after urine application has been observed before (Barneze et al, 2015) and also from fertiliser application by (Krol et al, 2016). These later peaks could be the result of newly formed available N after the initial application of the treatments (and appearance of the initial peak) and also due to the priming of the microbial activity.…”

Grassland renovation has important consequences for C and N cycling and losses

“…Nutrient emissions occur as gaseous losses and leaching (MacDonald, Chantigny et al., ). Emissions of CO 2 are related to soil mineralization (Willems et al., ), and N 2 O mainly to enhanced N turnover and fertilization (Merbold et al., ) with the additional risk of indirect N 2 O emissions that are related to larger NO 3 leaching losses (Davies et al., ; Krol et al., ; MacDonald, Rochette et al., ). Only techniques with no or minimal destruction of the old sward seem to be positive where emissions are concerned.…”