Lack of increased availability of root-derived C may explain the low N2O emission from low N-urine patches

Abstract

and CO 2 emissions from the monoliths as well as δ 13 C signal of evolved CO 2 were done on day -4, -1, 0, 1, 2, 4, 5, 6 and 7 after application of urine corresponding to 3.1 and 5.5 g N m -2 in the first and second experiment, respectively. The δ 13 C signal was also determined for soil organic matter, dissolved organic C and CO 2 evolved by microbial respiration. In addition, denitrifying enzyme activity (DEA) and nitrifying enzyme activity (NEA) were measured on day -1, 2 and 7 after the first urine application event. Urine did not affect DEA, whereas NEA was enhanced 2 days after urine application. In the first experiment, urine had no significant effect on the N 2 O flux, which was generally low (-8 to 14 μg N 2 O-N m -2 h -1 ). After the second application event, the N 2 O emission increased significantly to 87 μg N 2 O-N m -2 h -1 and the N 2 O emission factor for the added urine-N was 0.18 %. However, the associated 13 C signal of soil respiration was unaffected by urine. Consequently, the increased N 2 O emission from the simulated low N-urine patches was not caused by enhanced denitrification stimulated by labile compounds released from scorched plant roots.

Importance of point sources on regional nitrous oxide fluxes in semi-arid steppe of Inner Mongolia, China

“…In contrast to several studies, which showed that N 2 O emissions from urine and dung/faeces patches are mostly significantly increased (Lovell and Jarvis 1996;Mosier et al 1998;Yamulki et al 1998;Petersen et al 2004;Clough et al 2004;van Groeningen et al 2005;Ma et al 2006;Carter et al 2006), we failed to demonstrate a significant stimulating effect of urine and faeces additions on N 2 O emissions for steppe soils in Inner Mongolia. In the case of faeces dropped at steppe sites we hypothesise that the lack of a stimulating effect on N 2 O emissions was due to the quick drying of faeces after its exposure to the ''dry'' climatic conditions in the field.…”

Effect of the application of cattle urine with or without the nitrification inhibitor DCD, and dung on greenhouse gas emissions from a UK grassland soil

“…This would suggest that nitrification could have had a predominant role as a source of emissions in our experiments. Similar results were shown by (Bol et al, 2004, Carter et al, 2006) in a Danish pasture. Carter et al (2006) also attributed N 2 O emissions from nitrification after application of low N urine (0.7 g N l −1 ) to a sandy soil.…”

“…Similar results were shown by (Bol et al, 2004, Carter et al, 2006) in a Danish pasture. Carter et al (2006) also attributed N 2 O emissions from nitrification after application of low N urine (0.7 g N l −1 ) to a sandy soil. They claimed that, under high N urine, nitrification will be inhibited for few days, possibly due to root scorching.…”

Effects of bovine urine, plants and temperature on N2O and CO2 emissions from a sub-tropical soil

“…Without plant-derived readily available C, soil N 2 O emissions have been reported to be low under urine patches (Carter et al 2006 Significance refers to the comparison between temperature/plant/urine treatments. ***p<0.001; **p<0.01; *p<0.05; ns (not significant) Table 4 Leaf and root dry weight biomass (g pot −1 ) and nitrogen updake (mg pot −1 ) at the end of the experiment (672 h following the urine treatment).…”