Quality of Organic Resource Influence on Soil Nitrous Oxide (N2o) Emission Under Maize (Zea Mays L.) Based Cropping System

Abstract

Integrated Soil Fertility Management (ISFM) has been recommended to address challenges of low soil fertility, by incorporating locally available organic resources (ORs) together with inorganic nitrogen (N) fertilizers. Despite ISFM success in field trials, there is limited information on ORs contribution to atmospheric greenhouse gas concentrations through nitrous oxide (N2O) emission. A short-term field study was conducted at two sites with different soil types; silt loam (Aludeka) and silty-clay soil (Sidada), to determine the effects of selected ORs (Calliandra carothyrsus (CL), farmyard manure (FYM) and maize stover (MS)) and their combination with inorganic N fertilizer on soil N2O emissions, available soil nitrogen and maize yields. The study also evaluated the relationship between N2O emissions and soil organic carbon (SOC), total nitrogen (TN), soil temperature, moisture content, soil nitrate (NO3-) and ammonium (NH4+). Static manual chambers were set up in the field to collect gas samples to quantify soil N2O emission. Relative to the control (0.19±0.1 Kg N2O-N ha-1), cumulative N2O emissions were significantly (P= 0.01) higher by 6, 9 and 13 fold under MS +N (1.05±0.8 Kg N2O-N ha-1), FYM +N (1.74±0.8 Kg N2O-N ha-1) and CL +N (2.54±1.2 Kg N2O-N ha-1), respectively at the Aludeka. At Sidada, cumulative N2O emissions were similar across all the treatments (P = 0.149). Approximately 240% and 411% of increase in cumulative N2O emissions across treatments at Sidada and Aludeka, respectively, was related to inorganic N fertilizer application. At Aludeka, cumulative N2O emissions exhibited significant positive relationship with SOC (r = 760, P = 0.029), TN (r = 0.820, P = 0.013), NO3-(r = 0.905, P = 0.002) and NH4+ (r = 0.738, P = 0.036), and negatively correlated with soil C:N ratio (r = -0.710, P = 0.049), soil pH (r = -0.739, P=0.036). At Sidada only NO3- (r = 0.711, P =0.048) exhibited a significant positive correlation with cumulative N2O emissions. In terms of grain yield at Aludeka, there was a significant (P < 0.001) effect of treatments on maize grain yield, with no observed significant effect at Sidada (P>0.05). FYM +N treatment recorded the highest mean maize grain yield at both Aludeka (10.63 t ha−1) and Sidada (9.23 t ha−1). In Aludeka site, treatments with ORs in combination with inorganic N fertilizers increased maize grain yield in comparison with those without. The study suggests that influence of OR on N2O emissions in maize based-cropping system vary depending on the type of soil and increases when OR are applied in combination with inorganic N fertilizers. A more understanding of the prevailing environmental soil conditions especially on soil texture is necessary for finding the best treatment combination in terms of yield and N2O emission reduction under the ISFM approach.