N2O emissions from arable systems are an important contributor to greenhouse gas emissions in the UK. Previous work has concentrated on emissions following application of fertilisers; however, recent studies have suggested that emissions during autumn/winter may be more important than thought previously, hence total emissions may have been underestimated. This work will aim to quantify N2O emissions from arable soils following incorporation of barley, sugar beet and pea residues on light soils, and barley and oilseed rape residues on heavy soils. Emissions following shallow incorporation and incorporation by ploughing will be compared, as will emissions from residues incorporated in August, October and February.
Effects of environmental and other variables (e.g. metalisable carbon, temperature, moisture, nitrate) on N2O emissions will also be evaluated, and the hypothesis that the interaction between timing/method of residue incorporation and soil moisture affects the balance between nitrate leached and N lost as N2O will be tested. Measurements will be performed at 2 sites with different soil/crop situations in each of 2 years, and will take place on each day for 6 days following residue incorporation and on 32 additional occasions during the study, thus ensuring that measurements are made under a range of environmental conditions. A number of statistical considerations have been incorporated to ensure that results represent accurate estimates of N2O emissions from crop residues in the UK.
These include: multiple measurements from each plot; time-series analysis of treatment effects and determination of the threshold measurable N2O level; distinguishing between sampling, operator and analysis errors and those due to treatment effects; and influence of temperature variations throughout the day on emission levels. The following determinations will then be performed: N2O emission; N incorporation in residues; SMN and moisture content; soluble C, mineralization rate; rainfall and soil temperature at 10 cm; and N leached.