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

Abstract

Summary 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 NH 4 NO 3 was dissolved in irrigation water and split into six applications ( F ertigation treatment). In the non‐fertigated soil ( ANS treatment), granular NH 4 NO 3 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 ( N 2 O ) and methane ( CH 4 ), measurements were made at six different distances from the irrigation distributor point (dripper). An additional field experiment with 15 N ‐labelled N fertilizer was carried out in parallel, with the aim of evaluating the contribution of nitrification and denitrification to the total N 2 O flux. Two different sources of 15 N were applied: 15 NH 4 NO 3 (20 at% excess 15 N ) ( 15 NH 4 + treatment, TR1 ) and NH 4 15 NO 3 (20 at% excess 15 N ) ( 15 NO 3 − treatment, TR2 ). Results indicated that both treatments ( ANS and F ertigation) had small emission fluxes of N 2 O (< 0.1% of N applied). However, F ertigation produced larger emissions (175.3 g N 2 O‐N ha −1 ) than ANS (90.1 g N 2 O N ha −1 ), with the pattern of N 2 O emission being strongly influenced by nitrification in both systems. Denitrification also contributed to emissions of 15 N 2 O but mainly on the day after fertilizer application in the F ertigation treatment. Methane fluxes were also affected by N fertilizer, with a decrease in the sink effect for CH 4 when NH 4 + was present in the soil.