The decomposition rate of crop residues in a soil is controlled by the C/N ratio of the material, the contact between the soil matrix and the residues, and environmental factors, including temperature, water content and nutrient availability (Varela et al. 2014). Residues with less C/N ratio offer a less N-constrained environment for microorganism growth and reproduction than those with high C/N relation, as it decomposes and mineralizes faster (Gul and Whalen 2013). Soil N 2 O is generated by microbial nitrification and denitrification processes. These processes are regulated by N availability (mainly NO 3 – ) and soil water content among other factors (Steenwerth and Belina 2008, Cosentino et al. 2013). Soil N availability depends on the decomposition rate of the stubble. Therefore, soil-residue contact and stubble quality (C/N ratio) affect the dynamics (timing and magnitude) of N 2 O emissions (Aulakh et al. 1991). Stubble N 2 O emission was studied in various crops (sugarcane, sorghum, cotton, rice and let- tuce (Huang et al. 2004, Muhammad et al. 2010). Soybean and corn are the most important summer crops in the Argentine cropping region, so it was considered of great importance to study the ef- fects of their residue decomposition on dynamic of N 2 O soil emissions. The aim of the present study was to evaluate the effect of the C/N ratio of soybean and corn stubble and the degree of contact between crop residues and the soil matrix on soil N 2 O emissions. Influence of stubble quality and degree of soil-stubble contact on N 2 O emission Vanina Rosa Noemí COSENTINO 1, *, Mariana G. MINERVINI 2 , Miguel A. TABOADA 1,2 1 Soils Institute, Natural Resources Research Center, Buenos Aires, Argentina 2 National Research Council Scientific and Technical, Caba, Argentina *Corresponding author: cosentino.vanina@inta.gob.ar ABSTRACT Cosentino V.R.N., Minervini M.G., Taboada M.A. (2017): Infuence of stubble quality and degree of soil-stubble contact on N 2 O emission. Plant Soil Environ., 63: 289–294. Te organic residue position and C/N ratio regulate decomposition rate and, therefore, nitrogen (N) release to the soil. Te N 2 O emission from soil is produced by nitrifcation and denitrifcation processes. Tese processes are af- fected by the mineral N concentration, water flled pore space (WFPS) and soil temperature. Te N 2 O emission from soils covered by corn and soybean residues has been little studied so far. Te aim of the present study was to evaluate the C/N ratio of corn and soybean residues and their contact degree with the soil on soil N 2 O emissions. A greenhouse experiment was conducted with a completely randomized design and N 2 O emission was determined using closed chambers. Te N 2 O emissions were afected by the residue position and not by its origin (soybean = corn). Treatments with residue on the surface had the highest N 2 O emissions at the beginning of the trial, while residue incorporation showed constant values of N 2 O emission during the experiment. Soil N 2 O emissions were explained by two controlling variables: the WFPS and the N-NO 3 – soil concentration. Te WFPS separated the emission values of N 2 O into two groups (threshold value near 77% WFPS). When the WFPS exceeded the threshold value, the emissions of N 2 O were partially explained by the concentration of N-NO 3 – soil. Keywords: greenhouse gas; soil matrix; crops 289 Plant Soil Environ. Vol. 63, 2017, No. 7: 289–294 doi: 10.17221/499/2016-PSE