Evaluation of mycorrhizae transplantation from Panicum maximum as biofertilizer for paddy cultivation in Sri Lanka

Indiscriminate chemical fertilization in paddy fields is causing detrimental global impacts, therefore exploration of bio-based sustainable alternatives to compensate requirement of chemical fertilizers is necessary. This study was designed to evaluate use of Arbuscular Mycorrhizal Fungi (AMF) obtained from roots of a spontaneous weed grass (Panicum maximum), which demonstrated an average AMF root colonization of 75-85%, as self-produced biofertilizer for rice cultivation. Field trial was carried out in paddy field at Monaragala, Sri Lanka. Two traditional rice (Oriza sativa L.) varieties (Suwadel and Kuruluthuda) were selected, and Randomized Complete Block Design was employed with three replicates in eight different treatment plots per block.  Different chemical fertilizer regimes (100%, 50% and 25% of recommended fertilizer dose) and no amendments as controls were applied. AMF inocula were applied alone or supplemented to fertilized treatments (100% +AMF, 50% +AMF, 25% +AMF, AMF alone). Treatment plan was implemented separately for two varieties. Rice yield and percentage of AMF root colonization were quantified at harvest. Results revealed that grain dry weight for Suwadel was significantly higher (p<0.05) in treatments supplying AMF in addition with chemical fertilizer at optimal dose (100%) or 50% reduced, compared to other treatments. Highest number of seeds was observed in plants treated with 100% fertilizer, but result was not significantly different (p>0.05) from 50% +AMF and 100% + AMF treatments. Treatments with AMF inocula alone showed highest percentages of AMF colonization in Suwadel. Inverse connection was observed between fertilizer level and AMF colonization. Differently from Suwadel, no AMF colonization was observed in Kuruluthuda variety and no significant differences were observed in harvest for treatments with and without AMF application. According to results, usage of AMF inocula as on-field prepared biofertilizer combined with 50% of chemical fertilizer is effective in improving sustainable agriculture but efficacy of application strictly depends on crop variety.