Can fertigation reduce nitrous oxide emissions from wheat and canola fields?

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• Increasing nitrogen fertilization and irrigation practices in agriculture are linked to elevated nitrous oxide (N₂O) emissions.
• Conventional nitrogen application involves a single application at crop seeding, which may not be optimal for mitigating greenhouse gas emissions.
• Nitrous oxide (N₂O) is a potent greenhouse gas with significant agricultural sources.

Purpose of the Study:

• To investigate the impact of splitting nitrogen (N) fertilization into seeding and in-crop fertigation on N₂O emission factors (EF) in irrigated wheat and canola.
• To compare the N₂O EF of conventional one-pass N fertilization with a split N application strategy.
• To evaluate the influence of different N rates and environmental conditions on N₂O emissions under varied N management.

Main Methods:

• Field experiment conducted over two growing seasons in Southern Alberta, Canada, with irrigated wheat (Triticum aestivum) and canola (Brassica napus).
• Comparison of one-pass N fertilization at seeding versus splitting total N into seeding and in-crop fertigation.
• Measurement of growing-season N₂O emission factors (EF) across multiple nitrogen application rates (60, 90, and 120 kg N ha^-1).

Main Results:

• Implementing N fertigation reduced average growing-season N₂O EF from 0.23 ± 0.03% (conventional) to 0.16 ± 0.04% (fertigation).
• Significant reductions in N₂O EF were observed with fertigation at low and intermediate N rates (60 and 90 kg N ha^-1), particularly in the second year with higher rainfall.
• The mitigating effect of fertigation diminished at the highest N rate (120 kg N ha^-1), and canola generally exhibited lower N₂O EF_yield ratios than wheat.

Conclusions:

• Splitting nitrogen fertilization with in-crop fertigation is an effective strategy for mitigating nitrous oxide (N₂O) emissions in irrigated wheat and canola systems.
• The benefits of fertigation in reducing N₂O emissions are more pronounced at lower to intermediate nitrogen rates and can be influenced by rainfall patterns.
• Optimizing N management through fertigation, especially with reduced N rates, offers a proactive approach to lower agricultural greenhouse gas emissions.