Synergistic effect of biochar and post-thermophilic stage application of supplemental Tithonia diversifolia on compost nutrient dynamics

Composting is a sustainable waste management technique that transforms organic matter into a valuable, soil amendment through processes such as thermophilic decomposition. However, thermophilic composting leads to a loss of important nutrients such as nitrogen by up to 50% in some cases. This is due to low-quality feedstock and loss of labile nutrients caused by high pile temperatures in the early phase of the process. Ultimately, the low quality of compost can potentially reduce soil fertility and crop productivity. We sought to enhance compost quality by biochar addition during heaping and supplemental Tithonia diversifolia application during post-thermophilic stages. We did a field setup of four composting treatments; Conventional practice; (Cattle manure + dry maize stalks + Lantana camara); L, Biochar compost (Cattle manure + dry maize stalks + Lantana camara + Biochar); B, Biochar compost + Tithonia diversifolia; post-thermophilic phase Tithonia diversifolia supplementation to L (LT) and B (BT). Sampling for physicochemical parameters analysis was done every 21 days over 84 days on each heap. We used assorted functions in the R statistical package (version 4.3.1) to plot the principal component analysis, correlation matrix, and analysis of variance among compost treatments. Total nitrogen exhibited significant positive correlations with all other variables. We also observed significantly higher nutrient levels in biochar-based composts than those without biochar amendment. Supplemental addition of Tithonia diversifolia in the post-thermophilic stage significantly increased nitrogen levels (1.59% in BT and 1.32% in LT compared to 1.34% and 1.24% in B and L, respectively). However, this addition led to a rise in pile temperature, prolonging the composting duration. We observed the highest nitrogen and organic carbon levels in BT (1.59% and 24.9%, respectively) at the end of the composting process. Our study recommends applying nutrient-boosting materials such as Tithonia diversifolia, in the post-thermophilic stage to minimize nutrient losses during composting.