Stimulus of nitrogen fertilizers and soil characteristics on maize yield and nitrous oxide emission from Ferric Luvisol in the Guinea Savanna agro-ecological zone of Ghana

Abstract

Farmers in Ghana rely on different forms of fertilizers to increase crop yields. The quantity of applied mineral N fertilizer is lost through nitrification and denitrification in the form of the powerful greenhouse gas nitrous oxide (N2O) has not been determined in the field until now. This study was conducted on a Ferric Luvisol in the Tolon District in Northern Ghana to determine the influence of nitrogen fertilizers, soil moisture and soil temperature on N2O emissions and grain yield. Three different nitrogenous fertilizers, i.e. ammonia sulfate (AS), urea (U) and NPK 60–40–40, were applied at either 60 or 120 kg N ha−1 yr−1 to maize, termed AS 60, AS 120, U 60, U 120 and NPK 60–40–40 thereafter. A control was left without N application. The results showed that N fertilizer type and quantities applied affected N2O emissions significantly. Plots of NPK 60–40–40, AS 60 and U 60 emitted 1.22, 1.45 and 1.79 kg N2ON ha−1, respectively, throughout the sampling period and were not considerably higher than N2O emissions from the control plots, which amounted to 0.32 kg N2ON ha−1. In contrast, the N2O emissions of U 120 and AS 120 were significantly higher than the controls, with values of 4.29 and 3.49 kg N2ON ha−1, respectively. When N2O flux was related to grain yield, 1.24 and 1.04 g N2O kg−1 grain was emitted from AS 120 and U 120, respectively. Plots treated with NPK 60–40–40, AS 60 and U 60 produced 0.39, 0.47 and 0.55 g N2O kg−1 grain, respectively, whereas plots without fertilization emitted 0.53 g N2O kg−1 grain. Average N-induced N2O emission factors ranged between 0.10% and 0.22%, with an overall emission factor of 0.15%. Keywords: Emission factor, N2O, Yield-based emission, Fertilizer