Soil N 2 O emissions with different reduced tillage methods during the establishment of Miscanthus in temperate grassland.

An increase in renewable energy and the planting of perennial bioenergy crops is expected in order to meet global greenhouse gas (GHG) targets. Nitrous oxide (N2 O) is a potent greenhouse gas, and this paper addresses a knowledge gap concerning soil N2 O emissions over the possible "hot spot" of land use conversion from established pasture to the biofuel crop Miscanthus . The work aims to quantify the impacts of this land use change on N2 O fluxes using three different cultivation methods. Three replicates of four treatments were established: Miscanthus x giganteus (Mxg) planted without tillage; Mxg planted with light tillage; a novel seed-based Miscanthus hybrid planted with light tillage under bio-degradable mulch film; and a control of uncultivated established grass pasture with sheep grazing. Soil N2 O fluxes were recorded every 2 weeks using static chambers starting from preconversion in April 2016 and continuing until the end of October 2017. Monthly soil samples were also taken and analysed for nitrate and ammonium. There was no significant difference in N2 O emissions between the different cultivation methods. However, in comparison with the uncultivated pasture, N2 O emissions from the cultivated Miscanthus plots were 550%-819% higher in the first year (April to December 2016) and 469%-485% higher in the second year (January to October 2017). When added to an estimated carbon cost for production over a 10 year crop lifetime (including crop management, harvest, and transportation), the measured N2 O conversion cost of 4.13 Mg CO2 -eq./ha represents a 44% increase in emission compared to the base case. This paper clearly shows the need to incorporate N2 O fluxes during Miscanthus establishment into assessments of GHG balances and life cycle analysis and provides vital knowledge needed for this process. This work therefore also helps to support policy decisions regarding the costs and benefits of land use change to Miscanthus .