Nitrogen leakages and vegetable dry matter yield in a subtropical wetland soil amended with cattle manure and mineral nitrogen fertiliser

Abstract

The response of nitrous oxide emission and nitrate leaching to increased nitrogen (N) fertiliser and cattle manure applications to wetland vegetable cropping in subtropical Africa have significant impacts on the atmospheric and terrestrial environments. Two field experiments were carried out in a wetland in central Zimbabwe in order to determine the effects of N fertiliser and cattle manure applications on emissions of N₂O, nitrate leaching and dry matter yield of rape and tomato. The static chamber and gas chromatography techniques were used to capture and measure fluxes of N2O. A station of buried lysimeters was employed to collect leachate for determining nitrate leaching losses. The experiments were in completely randomised block designs. The loss of N in nitrate leaching increased significantly with increasing rates of manure and mineral fertiliser applications. When the application rates of N fertiliser and manure were increased, the emissions of N₂O per unit harvested dry matter yield significantly decreased. Losses of N in N₂O emissions can be reduced by adopting agronomic practices that enhance N uptake and higher dry matter yield. The loss of N from applied fertilisers in nitrate leaching was 6–20 times greater than the loss of N in N₂O emissions in wetland vegetable production.

Keywords:

• climate change
• environment
• wetland agriculture