Effect of Plant-derived Biofertilizers (Azolla filiculoides and Tithonia diversifolia) on Growth and Yield Parameters of Lokpa Yam (Dioscorea cayenensis-rotundata) Grown on Distric Plinthic Ferralsol in the Forest Zone of Côte d'Ivoire

Aims: The study aims to assess the fertilizing potential of Azolla filiculoides and Tithonia diversifolia leaves on Lokpa (D-rotundata) yam cultivation in the forest zone of Côte d'Ivoire. Place and Duration of Study: The study took place over 9 months (April-December) in 2022 at M'Bayakoffikro in the Daloa department of central-western Côte d'Ivoire. Methodology: After clearing a soil fallow classified Distric plinthic ferralsol, microplots in randomized Fisher blocks of 2 replicates each with five treatments (Azolla filiculoides-AZ; Tithonia diversifolia with fresh biomass-TDF; Tithonia diversifolia with decomposed biomass-TDD; Azolla filiculoides + Tithonia diversifolia with fresh biomass-AZ+TDF and Azolla filiculoides + Tithonia diversifolia with decomposed biomass-AZ+TDD) and a control without fertilizer were delimited in which,10 mounds were levelled for sowing yam tuber pieces. Before sowing the tubers, the mounds were opened by hand and 0.5kg of each formulated fertilizer was ploughed in and then resealed. After 14 days of fertilization, the mounds were reopened and a single seedling was buried 20cm deep in each mound from top to bottom, followed by 300ml of water and then resealed. After germination, growth and production parameters were evaluated and the data obtained were subjected to an analysis of variance with Statistica 7.1 software at the 5% threshold. Results: The different biofertilizer formulations had a significant effect on all growth and yield parameters of lokpa yam (D-rotundata). However, the highest values for both growth and yield parameters compared with other fertilizers at all measurement times and at maturity were obtained with Azolla filiculoides combining decomposed Tithonia diversifolia leaves on the one hand and fresh Tithonia diversifolia leaves on the other. Conclusion: Improving soil productivity in forest areas by finding reliable and effective alternatives to mineral fertilizers is a necessity, and the combination of Azolla filiculoides and Tithonia diversifolia could be a good alternative for sustainable, environmentally-friendly agriculture.