Nutrient Management Research Database

Agricultural soil is a major source of nitrous oxide (N₂O), nitric oxide (NO) and ammonia (NH₃). Little information is available on emissions of these gases from soils amended with organic fertilizers at different soil water contents. N₂O, NO and NH₃ emissions were measured in large-scale incubations of a fresh sandy loam soil and amended with four organic fertilizers, [poultry litter (PL), composted plant residues (CP), sewage sludge pellets (SP) and cattle farm yard manure (CM)], urea fertilizer (UA) or a zero-N control (ZR) for 38 days. Fertilizers were added to soil at 40, 60 or 80% water-filled pore space (WFPS). The results showed that urea and organic fertilizer were important sources of N₂O and NO. Total N₂O and NO emissions from UA ranged from 0.04 to 0.62%, and 0.23 to 1.55% of applied N, respectively. Total N₂O and NO emissions from organic fertilizer treatments ranged from 0.01 to 1.65%, and <0.01 to 0.55% of applied N, respectively. The lower N₂O and NO emissions from CP and CM suggested that applying N is these forms could be a useful mitigation option. Comparison of the NO-N/N₂O-N ratio suggested that nitrification was more dominant in UA whereas denitrification was more dominant in the organic fertilizer treatments. Most N was lost from PL and UA as NH₃, and this was not influenced significantly by WFPS. Emissions of NH₃ from UA and PL ranged from 62.4 to 69.6%, and 3.17 to 6.11% of applied N, respectively.

This laboratory experiment investigated how a variety of organic fertilizers influenced nitrous oxide emissions when soil mositure content varied.

Soil was amended with either poultry litter, composted plant residues, sewage sludge pellets, cattle farm yard manure, or urea fertilizer at water contents of 40, 60, or 80% of WFPS.

Nitrous oxide and soil nitrogen levels were measured regularly over the 38 day experiment.

N₂O emissions increased as soil moisture increased for all fertilizers tested.

At 40% of water filled pore space, emissions did not differ between fertilizer types.

At 60% of water filled pore space, N₂O emissions were highest for the poultry litter and sewage sludge pellets as emissions were elevated in these treatments for 15 after fertilizer applications. At 80% of water filled pore space, elevated N₂O emissions were observed for 25 days following application of sewage sludge pellets, poultry litter, and urea applications. Emissions were in the order of sewage pellets > poultry litter > urea.

Emissions were lower from composted plant residues and cattle farm yard manure.