Greenhouse gas emissions in response to tillage, nitrogen fertilization, and manure application in the tropics

Cultivation of maize (Zea mays L.) can emit significant greenhouse gases (GHGs) due to root respiration, soil organic matter decomposition, and fertilizer losses in a tropical environment. Our objective was to examine the effect of tillage (conventional tillage [CT], minimum tillage [MT], and no-tillage [NT]), N fertilization rate (0, 90, and 120 kg N ha⁻¹), and manure application rate (0, 5, and 10 Mg ha⁻¹) on CO₂, N₂O, and CH₄ emissions under maize in two growing seasons (July-October 2018 and May-August 2019) in southwest Nigeria. We measured CO₂, N₂O, and CH₄ fluxes using the static chamber method and soil temperature and water content weekly, global warming potential (GWP), maize yield, and greenhouse gas intensity (GHGI). The CO₂ and N₂O fluxes peaked immediately following planting, fertilization, and intense precipitation, with most fluxes concentrated at 2–6 wk after planting. The CH₄ flux showed little change throughout the duration of the study. Cumulative CO₂ and N₂O fluxes were greater for CT and MT than NT, but cumulative CH₄ flux was greater for MT than CT and NT. Higher N fertilization rate increased N₂O and CH₄ fluxes. The GWP was greater for CT than MT and NT and greater for 90 than 0 kg N ha⁻¹. Maize yield was greater for MT than CT and NT and increased with higher N fertilization rate. The GHGI was lower for MT than CT and lower for 120 than 0 and 90 kg N ha⁻¹. Because of overall lower maize yield, MT with reduced N ferilization rate in split applications may be needed to reduce GHG emissions while sustaining yield in the sandy soils of southwest Nigeria.