Maize Residue Interaction with High Quality Organic Materials: Effects on Decomposition and Nutrient Release Dynamics

Abstract

The application of organic materials with wide carbon-to-nitrogen (C-to-N) ratios is known to cause initial immobilization of nutrients, unless N fertilizers are applied. In Sub-Saharan Africa, regular application of mineral fertilizers with organic residues is seldom practiced due to several socioeconomic constraints. In the present study, we assessed the biomass qualities of Zea mays, Tithonia diversifolia and Vicia faba and evaluated whether delayed decomposition and nutrient release of low quality residues will improve when mixed with high quality residues. Our hypothesis was that high quality organic residues have high N supply capabilities to improve decomposition and nutrient release of low quality materials when mixed together. Compared with V. faba and T. diversifolia biomasses, Z. mays residue was found to be relatively poor in quality as a result of its relatively low N concentration (10.8 g/kg) and wider C-to-N ratio (37.2:1). The assessment on biomass quality was consistent with the results on decomposition. After one week, 42 % of Z. mays residues had decomposed compared with more than 90 % of T. diversifolia and V. faba residues. Further, the decomposition and N release rate of Z. mays tripled when mixed with either T. diversifolia or V. faba biomass. In this study, the initial N, C, lignin, C-to-N ratio, lignin-to-N ratio and (lignin + polyphenol)/N ratio of the residues were useful indicators of degradability and nutrient release based on significant (P < 0.005) correlations. The study found that mixing Z. mays residue with either T. diversifolia or V. faba green biomass improved the N composition and C-to-N ratio of the mixture, which accounted for the improved decomposition and nutrient release rates of Z. mays residues in the mixture compared with sole Z. mays treatment. Our study therefore suggested that in places where inorganic fertilizers are limited, T. diversifolia and V. faba residues could be viable sources of N for improved decomposition and nutrient release of low quality residues.