Resumen de Improving maize residue use in soil fertility restoration by mixing with residues of low C-to-N ratio: effects on C and N mineralization and soil microbial biomass

S.T Partey, Richard F. Preziosi, G.D Robson

• The application of organic residues with wide C-to-N ratio on soils is known to cause nitrogen immobilization unless applied with nitrogen fertilizer. Considering that fertilizer usage is limited in low input agricultural systems in Africa. we determined whether it was possible to alleviate N immobilization of Zea mays (maize) by applying together with Tithonia diversifolia or Vicia faba green manure with low C-to-N ratio. The effect of sole Z. mays application on soil microbial biomass and carbon mineralization were also compared with when mixed with T. diversifolia or V. faba. The objectives were achieved using laboratory incubation experiments conducted over 84 days. As expected. the application of sole Z. mays residues resulted in an initial net N immobilization that lasted for 28 days. Relative to sole Z. mays. the application of Z. mays with either V. faba or T. diversifolia increased N mineralization by 58% and 55% respectively. It was also evident. that in comparison with sole Z. mays. soil microbial biomass and C mineralization were significantly higher in soils that received residues of V. faba and T. diversifolia either alone or in combination with Z. mays. The study showed that V. faba and T. diversifolia either alone or in combination with Z. mays residues had relatively high N concentration and narrow C-to-N ratio. which accounted for the increased N mineralization and improved microbial biomass and C mineralization. We inferred from the results of our study that N supplies from V. faba and T. diversifolia could be substantial in alleviating delayed decomposition and N immobilization of Z. mays residues.