Contribution of Arbuscular Mycorrhizal Fungi to Improving Maize Growth and Yield in the Low-Fertility Ultisols of Thailand

Restrictions in crop production in Ultisols are primarily due to low soil fertility, which limits their capacity to supply sufficient nutrients for plant growth. Importantly, arbuscular mycorrhizal fungi (AMF) can play a role in enhance nutrient availability for plants. This study aims to evaluate the effects of AMF inoculation combined with chemical fertilisation on maize growth and yield in three soil series of Ultisols. A pot experiment was performed with a 2 × 3 factorial CRD with five replications. Two factors were studied: (1) AMF (Glomus sp.) (non-AMF and AMF inoculation) and (2) rates of chemical fertiliser (0, 50, and 100% of the recommended fertiliser rate for maize, CF). The results showed that AMF significantly enhanced the growth and yield of maize at all CF rates across all soil series. Total biomass and grain yield following the AMF treatment were markedly higher than after the non-AMF treatment. Likewise, AMF significantly improved the photosynthetic physiology and NPK content of maize. The CF rate had a negative impact on AMF root colonisation, and the AMF efficiency also decreased as the CF rate increased. The relative mycorrhizal dependency (RMD) on maize growth and yield were the highest at 0% CF, with averages of 34.49% and 52.35%, but decreased to 7.43% and 8.73% at 100% CF, respectively. However, the RMD of maize growth and yield remained positive for soil series. These findings suggest that AMF are an effective means of supporting maize cultivation in Ultisols.