Effect of lime, dicyandiamide and soil water content on ammonia and nitrous oxide emissions following application of liquid hog manure to a marshland soil.

摘要

The loss of nitrogen (N) from field-applied animal manure through ammonia (NH3) volatilisation and nitrous oxide (N2O) emission is of major environmental concern. Both lime and dicyandiamide (DCD) have been suggested as amendments that can mitigate N2O emissions, but simultaneously increase the risk of NH3 volatilisation. This study evaluated the impact of lime and DCD on NH3 and N2O emissions following application of liquid hog manure. Hydrated lime (Ca(OH)2) was added to an acidic soil to achieve three pH levels (4.7, 6.3 and 7.4). Soil samples (100 g) were then placed in 500 ml screw-top Mason-jars and de-ionised water was added to bring the samples to 50, 70 and 90% water-filled pore space (WFPS). Slurry was applied at a rate equivalent to 116,000 l ha-1, while DCD was applied at 30% of the NH4-N rate applied. Jars were sealed and incubated at 21 degrees C for 21 d. Ammonia volatilisation was quantified using boric acid traps, while N2O gas concentration was analysed using gas chromatography. Dicyandiamide had no effect (P&0.05) on either NH3 or N2O emissions. Both NH3 and N2O emissions increased (P&0.05) as WFPS increased, with emissions ranging from 0.9 to 1.4 kg NH3-N ha-1 and 123 to 353 g N2O-N ha-1, respectively. Liming decreased (P&0.01) N2O emissions from 547 to 46 g N2O-N ha-1, but increased (p&0.01) NH3 volatilisation from 0.36 to 1.92 kg NH3-N ha-1. Results suggest that liming to a pH&=6.3 can reduce N2O emissions, however, this reduction will be accompanied by a substantial loss of NH3..