Carbon dioxide, methane and nitrous oxide emissions from furrows and hills in a cotton-wheat-fallow rotation, Narrabri, Australia

This study investigates the emissions of greenhouse gases, carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O), from different soil positions (hill, skip furrow, irrigation furrow) in a cotton-wheat-fallow rotation system under irrigation in Narrabri, Australia. The research spans a two-year period and aims to understand the spatial variability of emissions and their relation to soil and atmospheric conditions. Nitrous oxide emissions during the cotton season averaged 2.07 ± 0.13 kg N 2 O-N ha −1 , representing 0.86 % of applied inorganic N fertiliser nitrogen, with emissions occurring in hills and furrows due to nitrogen transport. Methane was consistently absorbed by the soil and contributed a small amount to the overall greenhouse gas budget. Carbon dioxide emissions were higher from furrows, while hills functioned as carbon sinks during cropping seasons. The rotation exhibited a net soil carbon loss of approximately 4.1 ± 0.5 t C ha −1 , indicating a need for management strategies to increase carbon inputs during fallow periods. Further, greenhouse gas measurements are required from all different soil positions (hill, skip furrow, irrigation furrow) as well as biophysical parameters. This is not only due to differences between each measurement location but also between the chamber and field measurement locations. Longer term measurements are required to improve the accuracy of emissions and carbon balance estimates. • Nitrous oxide emissions during the cotton season represented 0.86 % of the applied fertiliser-N (240 kg N ha -1 ). • Nitrous oxide emissions between the hill and irrigation furrow were different to the skip furrow during the cotton season. • Agronomic management should focus on improved NUE and increased plant biomass production.