Abstract

Ultisols are one of the marginal soils having high water retention but low plant available water, due to its high clay and low organic matter (OM) content. This research aimed to identify the role of biochar in improving plant available water and yield of edamame (Glycine max L. Merr) at Ultisols. This experiment was conducted at the field site, while soil samples were analyzed in the Soil Laboratory, Universitas Andalas, Padang. There were three types of biochar used in this study (derived from bamboo, rice husk, and young coconut waste feedstock) applied for 20 t/ha to the soil. This study had four treatments viz., control (no biochar applied), bamboo biochar (B-biochar), rice husk biochar (RH-biochar), and young coconut waste biochar (YCW-biochar). The treatment units were allocated based on Randomized Block Design (RBD) with five replicates. The parameters analyzed were plant available water (PAW), soil texture, OM, hydraulic conductivity (HC), bulk density (BD), total soil porosity (TSP), aggregate stability (AS), void ratio, degree of saturation, and yield of edamame. The results showed that, in general, the application of 3 types of biochar increased PAW from 13.5% (control) to 16.1%. This was due to the improvement of most of the soil's physical properties, especially soil OM increased from 1.5−3.32%, TSP from 53.76−57.54%, AS from 42.30−58.46%, HC rate from 1.84−5.02 cm/h, and decreased BD from 1.22−1.13 Mg/m3. Biochar also enhanced edamame fresh pod yield from 3.15 to 4.40 t/ha. Among the tested biochars, BB had the most significant effects on PAW, AS, and edamame yield. Thus, BB is recommended for improving Ultisol quality and supporting edamame production.