Evaluation of arbuscular mycorrhizal inoculum and compost application on the growth and yield of cassava (Manihot esculenta) under organic cultivation

Efficacy of arbuscular mycorrhizal (AM) inoculum and compost application on cultivation of cassava variety Hanatee (a sweet type) under organic farming are required to investigate for management in order to obtain high yield and quality of the cassava product. Therefore, an experiment was conducted during 2018 to 2020 at organic farm in Chiang Mai province, northern Thailand to examine the efficacy of inoculum product of AM fungi and leafcompost application on the growth, tuber yield and nutrient uptake of the cassava variety. Dominant species of AM fungi isolated from inoculum product (Aaulospora scrobiculataand A. tuberculata) were used for the study and sunn hemp acted as host plant for inoculum production. Four experimental treatments viz., control (without application of boththe AM fungal inoculum and compost), application of AM fungal inoculum without compost, application of compost without AM fungal inoculum, and applications of both AM fungal inoculum and compost were laid out in randomized block design with four replications. Nine months of cassava cultivation, the results showed that application of AM fungal inoculum increased growth, tuber yield and nutrient uptake of cassava variety Hanatee, especially the higher shoot dry weight (153.4 g/plant), tuber dry weight (229.3 g/plant), N andP contents in tuber (321.0 and 255.3 mg/plant, respectively) were recorded when inoculum of AM fungiwas used in combination with the compost application. Tuber dry weights of cassava in thetreatments applied only AM fungal inoculum, applied only compost, and applied both AM fungal inoculum in combination with compost were about 1.7, 5.1 and 11.4 times higher than the control treatment, respectively. Furthermore, compost application had positive impact on root colonization and spore densities of AM fungi in the cassava field. Therefore, this study highlights the use of AM fungi inoculum together with compost application for a move towards sustainable organic farming.