Table 1.
Yields and inputs for conventional and conservation wheat and popcorn crop rotations in 2017–2019 and 2018–2020.
WW = Winter Wheat; PC = Popcorn. The year indicates the harvest year. Unless indicated otherwise, inputs of cover crops were attributed to conservation popcorn. For conservation agriculture yields and inputs were based on field data, for conventional agriculture they were based on expert judgement.
Table 2.
Scenarios of conventional and conservation popcorn and wheat crop rotations.
Table 3.
Main direct emissions for conventional and conservation wheat and popcorn crop rotations in 2017–2019 and 2018–2020.
WW = Winter Wheat; PC = Popcorn. The year indicates the harvest year. Unless indicated otherwise, direct emissions of cover crops were attributed to conservation popcorn.
Table 4.
Carbon (C) balance per crop and its components for wheat and popcorn estimated by the AMG model: Organic C input from cash-crop residues (Ccrop), mineralisation of soil C (Cmin), organic C input from cover crops (Ccover), organic C input from compost (Ccomp), and humified C sequestered Cseq) for the conventional and conservation rotations.
Values are expressed as t C/ha/year at a depth of 0–30 cm. Values in brackets for Cseq of the conventional crops correspond to the effects of a 10% increase or decrease of their yields.
Fig 1.
Contribution of soil organic carbon, direct emissions, seed, compost, mineral fertilisers, pesticides, field operations (including irrigation), and transport of inputs to the climate change impact for the two-year popcorn and wheat crop rotation in 2017–2019 and 2018–2020, for conventional and conservation rotations.
Dots indicate net impact, which is equal to C sequestration minus greenhouse gas emissions. The inputs and direct emissions of the cover crops were attributed to the popcorn crops.
Fig 2.
Contribution of direct emissions, seed, compost, mineral fertilisers, pesticides, irrigation, other field operations, and transport of inputs to the climate change impact for individual crops.
Values are means for 2017–2018 and 2018–2019 for wheat, for 2019 and 2020 for popcorn, and for 2018–2019 and 2019–2020 for cover crops.
Table 5.
Impacts of conventional and conservation crop rotations (2017–2019 and 2019–2020) for the land management (ha.year) functional unit.
Difference expresses impacts of the conservation rotation relative to those of the conventional rotation. Values in brackets for Difference correspond to the effects of a 10% increase or decrease of the conventional crop yields.
Fig 3.
Soil organic carbon stock (0–30 cm) over 100 years according to three scenarios of popcorn and wheat crop rotations as estimated by the SIMEOS-AMG simulation tool.
See Table 2 for a description of the scenarios.
Fig 4.
Contribution of direct emissions, seed, compost, other field operations, irrigation, mineral fertilisers, pesticides and transport of inputs to the climate change impact of conservation agriculture popcorn as a function of the percentage of impact allocated to compost: 7.2% (this study), 3.6% (50% decrease), 10.8% (50% increase), and 100% (original life cycle inventory from AGRIBALYSE; Avadi (2020)).
Fig 5.
Net climate change impact over 50 years considering greenhouse gas emissions and soil organic carbon sequestration according to three scenarios of popcorn and wheat crop rotations.
See Table 2 for a description of the scenarios.