Nutrient Management Research Database

Crop  residues  incorporated  in  soil  are  a  potentially  important  source  of  nitrous  oxide  (N2O),  though  poorly quantified. Here, we report on the N2O emission from 10 crop residues added to a sandy and a clay soil, both with2and without additional nitrate (NO3-). In the sandy soil, total N2O emission from wheat, maize, and barley residues32was not significantly different from the control. The total N2O emission from white cabbage, Brussels sprouts, mustard, sugar beet residues and broccoli ranged from 0.13 to 14.6 % of the amount of N added as residue and were higher with additional NO3- than without additional NO3-. In the clay soil, similar effects of crop residues33were found, but the magnitude of the N  O emission was much smaller than that in the sandy soil: less than 1% of the residue N evolved as N2O. The C-to-N ratio of the residue accounted for only 22-34% and the mineralizable N content  of  the  residue  for  18–74%  of  the  variance  in  N2O  emission.  We  suggest  that  the  current  IPCC methodology for estimating N2O emission from crop residues may be considerably improved by defining crop specific  emission  factors  instead  of  one  emission  factor  for  all  crop  residues.

This laboratory experiment investigated the role of incorporated crop residue carbon to nitrogen ratio on nitrous oxide emissions.

Residue from the following crops were incorporated into field moist soil (C:N ratio):

1. Wheat straw (72)
2. Barley straw (69)
3. Corn shoots (59)
4. White cabbage shoots (21)
5. Brussels sprouts shoots(14)
6. Broccoli shoots (14)
7. Yellow mustard shoots (9.8)
8. Sugar beat heads (32)

Each treatment was performed with and without supplemental nitrate amendment.

The effects of tillage and changing weather conditions were simulated in the lab.

Measurements of nitrous oxide emissions, carbon dioxide emissions, and biomass mineralization were all monitored for the duration of the 77 day experiment.

Emissions were highest in soils amended with Brussels sprouts, mustard, and broccoli that had high amounts of mineralizable N and narrow C:N ratios. 

Total N2O emissions from wheat, corn, and barley residues did not differ from the control that did not receive any residue inputs.

Cabbage, Brussels sprout, mustard, sugar beet, and broccoli residue incorporation were greater than the control. Emissions were generally higher from the sandy soil than from the clay soil.

Supplemental nitrate additions increased N2O emissions by around 100%.

N2O emissions rates were controlled by residue C to N ratio and availability of water soluble N.