Fertiliser inputs to crops usually create the largest increase in yield and quality of any of the crop input decisions but they are also the largest (\>50%) contributor to greenhouse gas (GHG) emissions associated with crop production. However, the crop production industry is very poor at matching the hundreds of fertiliser products available with the crop's nutrient requirements which leads to loss of yield and profit, increases in GHG emissions and other pollution such as ammonia emissions and nitrate leaching. Matching fertiliser product with crop requirement is very challenging because of the wide variation in crop requirement for the 12 essential nutrients and the wide range of fertiliser products available that contain different nutrients at different ratios. New start-up company 'Compass Agronomy' will lead the development of the first tool that identifies the optimum fertiliser product choice for both maximising gross margin and minimising GHG emissions and other pollutants. Ability to optimise both economic and carbon metrics is a particularly innovative and unique feature of the tool. The 'Fertiliser Optimiser tool' will rank fertiliser products for different output metrics: gross margin, GHG emissions, ammonia emissions, risk of nitrate leaching and phosphate run-off. The tool will enable a wide range of businesses to recover from the impact of COVID-19 by enabling: i) farm businesses to reduce unnecessary fertiliser costs and achieve greater crop yield and quality, ii) fertiliser distributors and manufacturers to have the trusted evidence to sell technically superior fertiliser products that increase the yield and quality of crops, iii) farm advisors to improve and expand the advice they can offer to not only include more accurate fertiliser recommendations to maximise gross margin, but also to optimise product choice to minimise GHGs and other pollutants. The tool will be accessible on-line, so these recommendations can be made without farmers and advisors having to physically meet. By identifying fertiliser products, which provide both the greatest gross margin and lowest environmental impact, the tool will ensure the recovery from COVID-19 will be cleaner than before and help transition crop production towards carbon net zero. In addition to helping farmers to reduce the carbon foot print of their crops, the tool will help the UK reach its target of reducing ammonia emissions, and help farmers reduce the risk of nitrate leaching and phosphorus run-off which cause eutrophication of water courses and cost millions of pounds to remove from water supplies.