Nitrous oxide emissions from long-term fertilized black soils in Harbin, China

At soil water content of 70% water holding capacity, different long-term fertilized black soils were incubated to investigate nitrous oxide (N ₂O) emission. Maximal N₂O emission was observed at the beginning of 24-h and 48-h incubation after the rewetting of dry soil. The treatment of combined normal fertilizer N, P with manure emitted the highest N₂O-N, was up to 737 μg kg^-1. Long-term application of fertilizer nitrogen combined with manure could efficiently increase N ₂O emission, and cumulative N₂O-N emissions of double fertilizer N plus double manure, normal fertilizer N plus manure and normal fertilizer N were 268, 162 and 148 μg kg^-1, respectively. Increasing application amount of manure could increase N₂O emission, and cumulative N₂O-N emissions of double manure and normal manure treatments were 131 and 116 μg kg^-1, respectively. Cumulative N₂O-N emission of double fertilizer N was 232 μg kg^-1, N₂O emission increased with the increase of nitrogen application. However, N₂O emission decreased with the increase of phosphorus application, and cumulative N₂O-N emissions of double fertilizer P and normal fertilizer P were 132 and 201μg kg^-1, respectively. Combined normal fertilizer NPK with manure emitted lower N₂O, and this treated soil could supply the necessary elements of crop and soil biota and balance soil fertility.