Abstract:
Nitrous oxide emissions are usually increased following incorporation of crop residues or inorganic N fertilizer into soil, but the effect of combining these inputs at different proportions on N dynamics and NO emissions has 2 yettobeadequatelyexamined.Theinteractiveeffectofcombiningcropresiduesbarley(Hordereumvulgare)and clover (Trifolium pretense) and inorganic N fertilizer (NHNO) on NO emission and mineral N dynamics under 4 3 2 controlledlaboratoryconditionsisreported.EmissionsofNOweresignificantlyhigherfromsoilsamendedwith 2 the low C:N ratio clover residues compared to the high C:N ratio barley residue treatments and was further increased, following combined application of crop residues and inorganic N fertilizer. Furthermore, the magnitude of emission was influenced by the proportions at which the residue-N and the fertilizer-N were -2combinedwiththe75:25fertiliser: clover treatment emitting the highest(P<0.05) amountof65mgNO-Nm 30 2-1 d. Incorporation of sole clover residues resulted in net N mineralization and addition of sole barley residues led to a net N immobilization. However, combined application of either residue with inorganic N fertilizer resulted in net N mineralization’s results from the study demonstrated that whilst there is the potential for NO emissionto 2 be controlled through varying ratios of residue: fertilizer input, the magnitude and direction of interactions between these N sources vary between different species as a result of their different qualities. This relationship should be verified under field conditions
