Nitrous oxide and methane emissions from a surface drip-irrigated system combined with fertilizer management.

摘要

Drip-fertigated systems have variable distributions of water and nutrients in the soil, which influence soil microbial activity. Because there is a lack of data on greenhouse gas (GHG) fluxes for these systems, a field experiment comparing drip irrigation systems (fertigated and non-fertigated) was carried out in a melon crop. For the fertigated treatment, nitrogen (N) as NH₄NO₃ was dissolved in irrigation water and split into six applications (Fertigation treatment). In the non-fertigated soil (ANS treatment), granular NH₄NO₃ was incorporated homogeneously into the upper part of soil surface at planting. A control treatment without N fertilizer was also included. In order to evaluate the pattern of nitrous oxide (N₂O) and methane (CH₄), measurements were made at six different distances from the irrigation distributor point (dripper). An additional field experiment with 15N-labelled N fertilizer was carried out in parallel, with the aim of evaluating the contribution of nitrification and denitrification to the total N₂O flux. Two different sources of 15N were applied: 15NH₄NO₃ (20 at% excess 15N) (15NH₄+ treatment, TR1) and NH₄15NO₃ (20 at% excess15N) (15NO₃- treatment, TR2). Results indicated that both treatments (ANS and Fertigation) had small emission fluxes of N₂O (<0.1% of N applied). However, Fertigation produced larger emissions (175.3 g N₂O-N ha-1) than ANS (90.1 g N₂O N ha-1), with the pattern of N₂O emission being strongly influenced by nitrification in both systems. Denitrification also contributed to emissions of 15N₂O but mainly on the day after fertilizer application in the Fertigation treatment. Methane fluxes were also affected by N fertilizer, with a decrease in the sink effect for CH₄ when NH₄+ was present in the soil.