Greenhouse Gas Emissions from Ferric Luvisols under Nitrogen Fertilization in Northern Ghana

Abstract

Carbon dioxide and nitrous oxide are two important greenhouse gas that contribute to global warming. Farmers in Northern Ghana rely on mineral fertilizers mainly sulphate of ammonia, urea and NPK compound fertilizers to boost crop production due to low soil fertility. A study was conducted on Ferric Luvisols in Akukayilli in the Tolon District of the Northern Region of Ghana to assess the influence of physic-chemical properties and environmental factors (soil temperature and soil moisture characteristics) on CO2, N2O, NO NO2 emissions. A randomized complete block design with three replications was used. Two nitrogenous fertilizer sources, sulphate of ammonia and urea at two rates of 60 and 120 kg N ha-1 y-1 and NPK (60-40-40) were used. Maize was the test crop, using the variety omankwa. The fate of excess N fertilizer in the soils were determined by 15N procedures. Application of NPK 60-40-40, sulphate of ammonia 60 and urea 60 kg ha-1 y-1 produced substantial maize yield with minimum production of CO2 and N2O. A nitrous oxide emission factor (EF) of 0.15 % has been established for the Northern savanna zone of Ghana. A large substrate availability (120 kg N ha-1 y-1) was found to contribute to the high emission of greenhouse gases, however, the levels of the greenhouse gases observed in this study are below the threshold that will lead to global warming. Observed δ15N values of N2O proved that the application of the compound fertilizer NPK fixed higher nitrogen in the soil than sulphate of ammonia and urea. Water filled pore spaces directly correlated with increase in emission of N gases. It is recommended that the emission factor be assessed for soils of other agro-climatic zone.