Improved NFT-NSS Chamber Systems for Rapid, Real-Time Nitrous Oxide Emissions from Livestock Manure and Soil.

A pilot-scale non-flow-through, non-steady-state (NFT-NSS) chamber system was designed for conducting greenhouse gas emission research on simulated open-lot beef feedyard manure surfaces. The system consisted of six, 1 m2 square chambers.  Nitrous oxide (N2O) concentrations were measured within the static chambers every second using a recirculating real-time analyzer (precision 0.1 ppbv).  Flux was calculated by monitoring the increase in N2O headspace concentration over time.  Installation of a small internal fan within the chamber lid decreased short-term N2O variation, allowing for quantification of N2O flux as low as 0.01 and as high as 400 mg/(m2-hr) in only a 30 to 60 sec measurement period.  N2O flux from beef manure was positively correlated with simulated rainfall (5 TRT, 0 to 51 mm, R2=0.99).  Each mm of rainfall resulted in 321 mg/m2 increase in total N2O emitted over the 45 d period.  Two distinct N2O peaks were observed after water addition.  At the highest rainfall (51 mm), the first peak occurred 2 h after water addition (peak height 400 mg/(m2-hr), duration 10 h) and the second peak occurred 15 d after water addition (peak height 55 mg/(m2-hr), duration 40 d).  The second peak accounted for 69 to 91% of the total mass of N2O emitted.  N2O flux followed a diurnal pattern, and was positively correlated with air and manure temperature.  A portable, real-time chamber system was also designed for field studies, where flux was quantified in 2 to 3 min from feedyards and natural soils.  These systems are an improvement over traditional GC-based flux chambers which require 30 to 60 min for individual flux measurements.