Impact of nitrogen fertilization on soil respiration and net ecosystem production in maize

Agriculture in the semi-arid is often challenged by overuse of nitrogen (N), inadequate soil water and heavy carbon emissions thereby threatening sustainability. Field experiments were conducted to investigate the effect of nitrogen fertilization levels (N0 – 0, N100 – 100, N200 – 200, N300 – 300 kg N/ha) on soil water dynamics, soil respiration (Rs), net ecosystem production (NEP), and biomass yields. Zero nitrogen soils decreased Rs by 23% and 16% compared to N300 and N200 soils, respectively. However, biomass yield was greatest under N300 compared with N0, which therefore translated into increased net primary production by 89% and NEP by 101% compared to N0. To a lesser extent, N200 increased net primary production by 69% and net ecosystem production by 79% compared to N0. Grain yields were greatest under N300 compared with N100 and N0, which therefore translated into increased carbon emission efficiency (CEE) by 53, 39 and 3% under N300 compared to N0, N100 and N200 treatments, respectively. There appears potential for 200 kg N/ha to be used to improve yield and increase CEE.