Nutrient Management Research Database

Emissions of N₂O were measured following combined applications of inorganic N fertiliser and crop residues to a silt loam soil in S.E. England, UK. Effects of cultivation technique and residue application on N₂O emissions were examined over 2 years. N₂O emissions were increased in the presence of residues and were further increased where NH₄NO₃ fertiliser (200 kg N ha⁻¹) was applied. Large fluxes of N₂O were measured from the zero till treatments after residue and fertiliser application, with 2.5 kg N₂O-N ha⁻¹ measured over the first 23 days after application of fertiliser in combination with rye (Secale cereale) residues under zero tillage. CO₂ emissions were larger in the zero till than in the conventional till treatments. A significant tillage/residue interaction was found. Highest emissions were measured from the conventionally tilled bean (Vicia faba) (1.0 kg N₂O-N ha⁻¹ emitted over 65 days) and zero tilled rye (3.5 kg N₂O-N ha⁻¹ over 65 days) treatments. This was attributed to rapid release of N following incorporation of bean residues in the conventionally tilled treatments, and availability of readily degradable C from the rye in the presence of anaerobic conditions under the mulch in the zero tilled treatments. Measurement of ¹⁵N-N₂O emission following application of ¹⁵N-labelled fertiliser to microplots indicated that surface mulching of residues in zero till treatments resulted in a greater proportion of fertiliser N being lost as N₂O than with incorporation of residues. Combined applications of ¹⁵N fertiliser and bean residues resulted in higher or lower emissions, depending on cultivation technique, when compared with the sum of N₂O from single applications. Such interactions have important implications for mitigation of N₂O from agricultural soils.

This study investigated the effects of plant residue applications on nitrous oxide emissions under conventional tillage (CT) and no-till (ZT). The study was conducted over two years.

Year 1

Ammonium nitrate was applied at two rates (0 and 180 lbs N/ac) to both the CT and ZT plots. All treatments received 2.7 tons/ac of wheat straw. In the CT the straw was incorporated at a 10 inch depth and was left on the surface under the ZT treatment. The plots were planted with corn.

Year 2

The same plots were planted with either field bean or rye over the winter. Both were cut and either incorporated (for CT) or left on the soil surface (ZT). The plots were then planted with corn and fertilized as in year 1.

Soil temperature, nitrous oxide and carbon dioxide emissions, and soil nitrogen levels were all measured.

Year 1

Nitrous oxide emissions were higher in ZT than in CT for the 79 days following residue incorporation. The application of plant residues and fertilizer increased nitrous oxide emissions in the ZT plots. Fertilization increased emissions under CT.  Soil ammonium was elevated under CT as compared to NT.

Year 2

Fertilization increased emissions for both ZT and CT. The highest emissions were observed from fertilized rye under ZT. Fertilized rye ZT emissions were greater than fertilized bean ZT. In CT, emissions were higher from bean residue than rye residue, for fertilized and unfertilized plots alike.