Effect of split application of fertilizer nitrogen on N2O emissions from potatoes.
Burton, D.L., Zebarth, B.J., Gillam, K.M., and MacLeod, J.A. (2008). "Effect of split application of fertilizer nitrogen on N2O emissions from potatoes.", Canadian Journal of Soil Science, 88(2), pp. 229-239. doi : 10.4141/CJSS06007
The timing of fertilizer nitrogen (N) application influences the availability of NO3- as a substrate for denitrification. This study examined the effect of split application of fertilizer N on N2O emissions and denitrification rate in potato (Solanum tuberosum L.) production over 2 yr. Three treatments were used: 0 or 200 kg N ha-1 at planting, and 120 kg N ha-1 at planting plus 80 kg N ha-1 at final hilling. Fertilizer N application increased cumulative N2O emissions. Split fertilizer N application decreased cumulative N2O emissions in 2003, but not in 2002, compared with all fertilizer N applied at planting. A greater proportion of N2O emissions occurred between planting and hilling in 2003 (67%) compared with 2002 (17%). In 2003, the higher emissions during this period resulted from the coincidence of high soil NO3-availability and increased rainfall resulting in reduced aeration. Split N application was effective in reducing N2O emissions by minimizing the supply of NO3- when demand for terminal electron acceptors was high. N2O emissions were higher in the potato hill relative to the furrow; however, denitrification rate was higher in the furrow. Nitrate intensity (NI) expresses the exposure of the soil microbial population to NO3- and was calculated as the summation of daily soil nitrate concentration over the monitoring period. Cumulative N2O emissions were positively related to NI across year, N fertility treatment and row location. Denitrification was not related to NI, reflecting the primary role of NO3- in influencing the N2O:N2 ratio of denitrification rather than the magnitude of the overall process. Split N application was an effective strategy for reducing N2O emissions in years where there was significant rainfall during the period between planting and hilling.