Pathways towards Net Zero emissions in grain cropping farms

Markets and society increasingly demand food production systems that better balance production, profits, and environmental outcomes. Alternative pathways towards achieving NetZero emissions in grain cropping farms can be expected to have benefits and trade-offs across the multiple dimensions of sustainable agriculture, e.g., profits, environment, society and risks. To (i) incorporate capabilities in a whole-farm model to simulate cradle-to-farm gate boundary greenhouse gas emissions, (ii) use a whole-farm model to estimate trade-offs between pathways towards NetZero on three case study farms of Queensland Australia under historical and expected future climate scenarios, and (iii) analyse the influence of site conditions across the main grain growing regions of Queensland Australia on GHG emissions, gross margin (GM), risks, and the need for offsets. Using expert consultations and literature analysis we parameterised the whole farm modelling framework APSFarm NextGen and quantified NetZero pathways for grain farms. The model was used to simulate six farm management strategies, including (i) opportunistic, (ii) rigid, (iii) conventional high input strategy, (iv) conservation, (v) agroecology, and (vi) a NetZero approach that used afforestation as an offset. Historical climate (1970–2019), and 2021–2070 climate projections were used together with three Shared Socioeconomic Pathways (SSP): SSP126, SSP245, and SSP585. We assessed site conditions i.e., soil and climate, on gross margin, downside risks, and GHG emissions. The mitigation strategies tested here reduced GHG emission intensities but wouldn't achieve Net Zero emissions. Across three case study sites, between 4 % and 14 % of the farm area would need to be afforested to achieve NetZero. NetZero strategies showed, on average, 10.5 % lower GM than the baseline strategies (opportunistic and rigid strategy). This economic impact is equivalent to 2.98 Australian Carbon Credit Units, based on Q1 2024 prices. Under future climate scenarios, achieving NetZero farms will require larger afforestation areas. Environmental factors influenced the outputs: GHG emissions were positively correlated with mean air temperatures, annual precipitation, and soil bulk density. As expected, GM was positively correlated with an aridity index i.e., higher GM in wetter environments. Downside risk, i.e., the probability of achieving a negative return, was negatively correlated with aridity index, i.e., lower risks in wetter environments. Achieving NetZero in Australia's grain farms is likely to require offsetting emissions and factoring in lower profits. Model outputs could be used to inform expected trade-offs between economic and environmental outcomes in agriculture's pathways towards NetZero. The APSFarm NextGen model can be easily adapted to be applied to other grain production systems, countries, and regions. • Mitigation strategies reduce GHG emission intensity but can't achieve NetZero. • Afforestation offsets would be an option to achieve NetZero farm. • In future climates, achieving NetZero will require larger offset areas. • Whole-farm models are useful to estimate trade-offs between pathways to NetZero.