Environmental impacts assessment of maize, soybean, and wheat production in the Southwest of São Paulo state: alternative scenarios for the substitution of chemical fertilization

Mineral fertilizers are highly impactful in the agricultural sector, and animal manure can be an alternative to mitigate its impacts. The goal of this research was to estimate the potential environmental impacts on the production of soybean, maize, and wheat at the Lagoa do Sino Farm School from the Federal University of Sao Carlos, contemplating the 2016/2017 cropping season and testing the replacement of 100%, 50%, and 30% of chemical fertilization by composted cow manure. Life Cycle Assessment (LCA) was the methodology used. The functional unit was one ton of each crop produced on farm. Impacts were also assessed for one hectare of production for each agricultural product investigated and the system boundary was a cradle-to-farm gate. Impacts were assessed using the CML 2000 world+ method for abiotic depletion, global warming, acidification, and eutrophication. Chemical fertilization was the main hotspot for all crops produced. Soybean showed a potential impact of 1489 MJ, 125 kg CO2 eq., 0.6 kg SO2 eq., and 0.4 kg PO4 eq.; the production of maize 1497 MJ, 197 kg CO2 eq., 1 kg SO2 eq., and 0.8 kg PO4 eq.; and the production of wheat 5863 MJ, 632 kg CO2 eq., 3.3 kg SO2 eq., and 2.4 kg PO4 eq. The 30% substitution scenario was the most efficient observed since there is an increase in fuel consumption if distribution of larger amounts of manure are needed. Enriching the manure and investing in fossil fuel substitution will improve the environmental profile of the crops produced under intensive systems in the Southwest state of Sao Paulo, Brazil.