FALL SEMESTER - October 14

October 14

Thinking about today's class on Manures and the Nitrogen Cycle, i made the connection to an interesting paper I read a few year ago by Eagle et al. Here's an extract of theta hundred and so paper.

N₂O mitigation potential of agricultural land management through irrigation (Eagle et al. 2008)

The use of irrigation in agricultural fields is known to increases the potential of N₂O emissions by means of reducing aeration in the soil and increasing microbial activity. Studies comparing irrigated versus non-irrigated fields show an increased N₂O flux of 0.05 t CO₂e ha-1 yr-1 on irrigated versus non-irrigated turf grass (Bremer 2006), and an average difference of approximately 0.7 t CO2 e ha-1  yr-1  between 28 dry land and 13 irrigated land experiments (Liebig et al. 2005).

There is a significant number of “best management irrigation practices” available to mitigate N₂O emissions in agricultural fields. Studies show that by reducing the total amount of water applied and optimizing water distribution to root zones, irrigation efficiency gains can provide water savings as well as GHG benefits. Total N₂O emissions after a reduction in irrigation intensity have been measured to decrease by between 0.1 t CO2e ha-1 yr-1 and 0.9 t CO2 e ha-1 yr-1 (Rochette et al. 2008, Scheer et al. 2008, both studies taken from in Eagle et al. 2012). Scheer et al. (2008) determined that reducing irrigation intensity (irrigating cotton when soil moisture was at 65% instead of 75% of field capacity) reduced N2 O emissions by almost 50% (0.94 t CO2 e ha-1 yr-1), and similar effects were observed on winter wheat fi elds, although the total impact was lower because of lower baseline emissions (Eagle et al. 2012).

Studies by Kallenbach et al. (2010) and Amos et al. (2005) also documented significantly lower N₂O fluxes with drip and buried tape (versus surface) irrigation, although annual mitigation effects could not be determined because of relatively short-term flux measurements (Eagle et al. 2012).

Taken from: 

Eagle, A., L. Olander, L.R. Henry, K. Haugen-Kozyra, N. Millar, and G.P. Robertson. 2012. Greenhouse Gas

Mitigation Potential of Agricultural Land Management in the United States: A Synthesis of the Literature. Report NI

R 10-04, Third Edition. Durham, NC: Nicholas Institute for Environmental Policy Solutions, Duke University