Abstract:
Maize is cultivated in Sri Lanka with an average yield of 3.52 tonne/ha which is adequate for
40% of the local demand. Cultivation yield improvement is essential to reduce future maize
imports where chemical fertilizer application is a key factor at recommended rates, i.e., Urea:
350 kg/ha, Triple Super Phosphate: 100 kg/ha, and Muriate of Potash: 50 kg/ha. Chemical
fertilizer application is associated with many environmental impacts due to direct/indirect
emissions. A published study has not yet been reported in Sri Lanka with a proper evaluation of
environmental emissions/associated impacts from fertilizer application for maize. Therefore,
this study focused to evaluate the environmental emissions/associated impacts from fertilizer
application for maize cultivation in Sri Lanka. The evaluation of emissions/impact potentials
follows the life cycle approach which considered three main phases in the chemical fertilizer
application process, such as chemical fertilizer production, fertilizer transportation, and
fertilizer application. Emission calculations in fertilizer production and transportation phases
were performed by obtaining emission factors from the Ecoinvent 3.0 database and necessary
considerations. Airborne emissions (CO2, N2O, and NH3), groundwater leaching (heavy metals
and nitrates), and soil deposition (heavy metals and phosphorous) due to the fertilizer
application phase were calculated by using the standard Agri-footprint 4.0 methodology. Five
impact potentials: climate change, human toxicity, terrestrial ecotoxicity, freshwater ecotoxicity,
and marine ecotoxicity were evaluated and compared. Impact potentials were evaluated by
using the ReCiPe world (H) V1.12 impact assessment method in the SimaPro Life Cycle
Assessment software. Emission results showed that fertilizer production and transportation
phases released lower pollutant levels, compared to the application phase. Impact results
revealed that 92% of the climate change impact is contributed by the fertilizer application
phase. Soil deposition from fertilizer application devotes the highest influences (above 98%) in
human eco-toxicity and terrestrial eco-toxicity impacts. Freshwater eco-toxicity and marine eco toxicity impact results were 0.26 kg 1,4-dichlorobenzene eq and 0.22 kg 1,4-dichlorobenzene
eq, respectively where groundwater leaching of heavy metals from fertilizer application
contribute more than 80%. The findings from this study quantify the current levels of
environmental impacts that support future decision making for environmentally-benign
fertilizer application for maize cultivation in Sri Lanka.
