Soil compaction and fertilization effects on nitrous oxide and methane fluxes in potato fields

This study was conducted to determine the effect of soil compaction and N fertilization on the fluxes of N2O and CH4 in a soil (fine-silty Dystric Eutrochrept) planted with potato (Solanum tuberosum L,), Fluxes of N2O and CH4 were measured weekly for 1 yr on two differently fertilized (50 and 150 kg N ha(-1)) fields, For the potato cropping period (May-September) these fluxes were quantified separately for the ridges (soil bulk density rho(b) = 1.05 Mg m(-3)) covering two-thirds of the total field area, and for the uncompacted (rho(b) = 1.26 Mg m(-3)) and the tractor-traffic-compacted (rho(b) = 1.56 Mg m(-3)) interrow soils, each of which made up one-sixth of the field area. The annual N2O-N emissions for the low and the high rates of N fertilization were 8 and 16 kg ha(-1), respectively. The major part (68%) of the total N2O release from the fields during the cropping period was emitted from the compacted tractor tramlines; emissions from the ridges made up only 23%, The annual CH4-C uptake was 140 and 118 g ha(-1) for the low and high levels of fertilization, respectively. The ridge soil and the uncompacted interrow had mean CH4-C oxidation rates of 3.8 and 0.8 mu g m(-2) h(-1), respectively; however, the tractor-compacted soil released CH4 at 2.1 mu g CH4-C m(-2) h(-1). The results indicate that soil compaction was probably the main reason for increased N2O emission and reduced CH4 uptake of potato-cropped fields.