Soil N₂O emission and its agronomic efficiency under different tillage

Cultivated land soil is regarded as an important source of N₂O emission that is affected by farming practices. To determine effects of tillage and crop residues management on soil N₂O emission and it’s agronomic efficiency on the North China Plain, a field experiment was carried out, which contained 4 treatments with 3 replications. The 4 treatments were conventional tillage with crop residues incorporation to soil (CT+) and without crop residues incorporation to soil (CT), no-tillage with crop residues mulching (NT+) and without crop residues mulching (NT). During the field experimentation soil N₂O emissions at soil/atmosphere interface were sampled and analyzed by using static chamber-Gas Chromatography (GC) method in continuous 3 wheat growth seasons; meanwhile, the primary related factors with N₂O emission were also investigated and analyzed. The results showed that the dynamic changes of soil N₂O emission during wheat growth were similar but the cumulative N₂O emissions were significantly different under 4 treatments and, the interactive effect between tillage and crop residues management was significant. The cumulative N₂O emission per unit area under CT+ and NT+ were higher than those under CT and NT by 26.2% and 74.6%, respectively, and CT treatment emitted 42.4% more N₂O than NT treatment. The soil N₂O emission was greatly influenced by soil temperature and soil moisture. The correlation analysis indicated that there was a significant positive correlation between soil N₂O emission and both soil temperature at 5 cm depth soil and water filled pore space (WFPS), while there was a significantly negative relation between soil N₂O emission and dissolved organic nitrogen (DON). When assessing soil N₂O emission in relation to crop productivity expressed as above-ground N uptake (i.e. yield-scaled and nitrogen input-scaled N₂O emission), the soil N₂O emissions per kilogram grain yield were 0.180.73 g N₂O-N and per kilogram nitrogen input were 5.118.0 g N₂O-N. Although grain yield and nitrogen productivity were not significantly different among treatments, the N₂O emissions in relation to crop productivity were still significantly different among treatments, similar to the N₂O emission per unit area that were also greater under CT+ and NT+ than under CT and NT. In conclusion, no-till practice is help to reduce N₂O emissions from arable land soil in the North China Plain.