Nitrous oxide emissions from irrigated cotton fields – variations in time and space

Abstract

Key findings •• Nitrous oxide (N2O) emission into a closed chamber was found to be linear over our standard closure time of 60 minutes in three of the four chambers tested. •• Beginning N2O sampling at 9:00–9:30 am appeared to underestimate the daily average N2O flux, although there was no significant time effect in the higher emitting treatment. The sampling time was changed for the following season to start at 10:00–10:30 am. •• The average flux from the four manual chamber locations used in the main experiments (irrigated furrow, non-irrigated furrow, fertilised side of plant bed, non-fertilised side of plant bed) were found to give a good approximation of the N2O flux averaged across 12 chambers covering all possible locations in a two metre cross section of the cotton field. •• These tests validated the assumptions made in devising the sampling strategy used in subsequent experiments.