Effects of Soil Amendment with Compost and Mycorrhiza on Growth and Yield of White Yam (Dioscorea rotundata Poir.) Under Adamawa Field Conditions

Yam cultivation helps to improve the stability of the food system and increases the predictability of farmers' incomes. To obtain good yields, yams require soils rich in organic matter and nitrogen. Two trials were carried out at Wakwa in 2023 and 2024, a locality within the high Guinean savannahs of Cameroon, to study the influence of organic and biological fertilisers on the growth and yield of D. rotundata, in a bid to develop a sustainable production strategy for this species. Experiments involved five treatments 2:3 compost/soil ratio; 30 g of mycorrhizal inoculum; 30 g of mycorrhizal inoculum + 2:3 compost/soil ratio; zero NPK; the equivalence of 300 kg/ha of NPK 10 10 30, which were organised in a completely randomised block design and repeated three times. Soil sampling was carried out in the top soil horizon between 0 and 20 cm before planting and after harvest. Growth parameters were measured from the 4th week after planting. The parameters used to assess yield at harvest were the number of tubers per plant, and the length and weight of tubers per plant. The soil analysis results showed moderate acidity (pH water = 5.7) and very low concentrations of available phosphorus (2.07 mg/kg) and nitrogen (0.22 mg/kg). The addition of the compost/soil mixture increased the soil pH (pHwater = 6). Phosphorus and nitrogen were levels increased by 92, 87 mg/kg and 0.14% respectively. The compost/soil + mycorrhiza mixture significantly and positively influenced vine height, number of leaves, collar diameter and branching compared with the negative control during the two cropping seasons. The response of D. rotundata to the amendment indicated that yield varying between 14 t/ha and 31.6 t/ha under treatment negative control and 2:3 compost/soil + mycorrhiza respectively. Based on the present findings Therefore, treatment 2:3 compost/soil + mycorrhiza ratio is strongly recommended for the sustainable and eco-friendly production of this yam variety.