Almost half of New Zealand’s greenhouse gas (GHG) emissions come from agriculture. Few maize growers have modelled their GHG losses and there is limited grower understanding of how to decrease GHG emissions from maize cropping systems.

A recently published paper1 co-authored by Pioneer® brand seeds and the Foundation for Arable Research (FAR) modelled annual GHG emissions for 12 maize silage production systems.

Maize Silage

Maize silage yields ranged from 15.0 to 26.8 tDM/ha (average 21.1 tDM/ha). N fertiliser application rate to the maize crop ranged from 131 to 310 kg/ha (average 220 kg/ha). Maize silage systems without livestock (n=3) had average biological GHG emissions of 1,850 gCO2e/ha. The range of emissions from non livestock silage systems was 1,697 to 2,096 kg CO2e/ha. Maize silage systems which included winter livestock produced average biological GHG emissions of between 1,512 to 6,135 kgCO2e/ha (average 3,543 kgCO2e/ha).

Discussion

In maize grain systems there were moderate to high correlations between annual biological GHG emissions and N-surplus (R2 =0.4876), and total fertiliser N applied (R2 = 0.7761). In contrast there were poor correlations between annual biological GHG emissions from maize silage systems and total fertiliser N applied (R2 = 0.097) and N-surplus (R2 = 0.068) in silage systems. This was likely due to the contribution of methane from winter grazing.

Summary

Some take home message for maize growers are:

1.  Know your number. Use one of the available tools to calculate the GHG loss for your farm.
2. Make sure your nitrogen application rate is appropriate. Set realistic paddock yield expectations for your maize crop and consider paddock history and soil available nitrogen levels before determining crop nitrogen inputs.
3. Consider the form, rate and timing of N application. Incorporate urea or apply it prior to rain where possible. Alternatively consider the cost: benefit of using urease-coated N products.
4. Account for livestock. If you want to reduce GHG losses from your farm, consider winter management options which do not include livestock.

1 Densley et al. 2022. Quantifying greenhouse gas losses from typical maize cropping systems and the impact of possible mitigation strategies using OverseerFM. In Press.

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