The research looks at the potential of Salicornia plant oil as a biodiesel source, which is important for lowering harmful and greenhouse gas emissions while also supporting sustainability and biodiversity. The study looks at how different cultivation and fertilisation techniques affect the proportion of seed oil converted into biodiesel through ultrasonic technique. The produced biodiesel samples comprise more than 35% saturated Fatty Acid Methyl Esters (FAME) and more than 50% unsaturated FAME, with a tiny proportion of non-FAME. GC analysis indicated that the seed oil conversion percentage ranged from 55-96%, with good purity and varying levels of alkyl ester content (52-95-5%). The iodine value, saponification value, cetane number, high heating value, density, and kinematic viscosity of the biodiesel samples were also investigated. Sample (16) satisfied the quality standards for good biodiesel fuel, and additional testing verified that it is the best biodiesel. Salicornia Bigelovii biodiesel satisfies the recommendations of American and European biodiesel standards, proving its potential as a diesel substitute for compression-ignition engines. HIGHLIGHTS • Salicornia bigelovii has great potential as a renewable and sustainable source of biodiesel. • In-situ transesterification process depends on cultivation and fertilization techniques used. • Salicornia biodiesel, from irrigated seeds with 25% seawater, met fuel standards. • Biodiesel had >35% saturated FAME and >50% unsaturated FAME content. • Optimal biodiesel yield from seeds of nitrogen and phosphorus fertilizers; and highest purity with nitrogen and potassium fertilizers Salicornia biodiesel meets quality criteria: high CN, low sulfur, viscosity, pour/cloud points, and HHV.