The effects of plant litter characteristics on its decomposition in soil or at the soil surface is of primary importance for adequate management of nutrients and carbon (C) in agro-ecosystems.

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The nitrous oxide (N 2 O) emitted from soil was monitored to investigate the effect of sugarcane straw removal on the mechanisms that make mulch a Bhot spot^of N 2 O emissions under subtropical conditions. We conducted a field experiment with the firstratoon sugarcane with four amounts of straw (0, 4, 8, and 12 Mg ha −1) at the soil surface combined with 0 or 100 kg urea-N ha −1. The urea-N was applied 52 days after straw application. Over the course of 1 year, we measured the N 2 O and carbon dioxide (CO 2) emissions, mineral nitrogen (N), soil moisture and temperature, and remaining straw carbon (C) and N in the mulch. We observed two Bhot moments^for N 2 O emissions: the first one immediately after sugarcane straw application to soil and the second one after fertilizer-N application. High amounts of straw left on the soil led to an increase in the water-filled pore space (WFPS), and both WFPS and straw-C were strongly correlated with N 2 Ofluxes.CumulativeN 2 O increased from 510 (0 Mg + N) to 1055 (12 Mg + N) g N 2 ON ha −1 for the fertilized straw treatments. The N 2 O emission factors (EFs) of the sugarcane straw N and the fertilizer-N increased linearly with straw quantity, i.e., were not constant but were lower than the IPCC default values. Over 70% of the cumulative N 2 O emissions measured in straw + fertilizer-N treatments for 1 year were attributed to the presence of straw mulch, which emphasized the importance of the straw layer at the soil surface as a hot spot for N 2 O emissions.