Nitrogen Fixation And Vegetative Growth Of Immature Oil Palm Inoculated With Bacillus Sphaericus (Strain Upmb-10)

Inorganic-N fertilizer is the most widely used input in agriculture and it is a major factor that limits crop growth and yield. However, excessive use of inorganic nitrogenous fertilizer could lead to hazardous effect to the agro-environment. Besides that, it would also increase total production cost of the agricultural sector especially in the oil palm industry, the largest income generator to Malaysian agricultural economy. Rapid losses of fertilizer-N through leaching would further increase the cost on oil palm production and make the sector less profitable. In recent times, there is an increased attention to biological nitrogen fixation (BNF) as an alternative or supplement to nitrogenous fertilizers through application of associative N2-fixing rhizobacteria which could be applied to oil palm. These beneficial plant growth promoting rhizobacteria (PGPR) have been reported to be efficient in fixing atmospheric nitrogen and stimulating growth of leguminous and non- leguminous crops. Thus, it could be used as a biofertilizer and bioenhancer for most crops. However, there has been no report on the beneficial effect of PGPR on early growth of young oil palms under field conditions. A field trial using 15N isotope was conducted to estimate the N2 fixing capacity of a single strain N2-fixing rhizobacterium, Bacillus sphaericus UPMB-10, and assess its effects on early growth of young oil palms. Results from a 240-day (D240) field experiment indicated that the Bacillus sphaericus rhizobacterial strain UPMB-10 is a potential biofertilizer for oil palm seedlings with a N2 fixing capacity of 63% Ndfa (N derived from atmosphere) (78 g N2 fixed palm-1) of the total N requirement of young oil palms (equivalent to 12 kg N ha-1 at 148 palms ha-1) over 8 months. B. sphaericus UPMB-10 inoculation stimulated higher N content (125 g palm-1) as compared to the uninoculated control (90 g palm-1) and also promoted a total dry matter accumulation of 11 kg palm-1 in comparison to the con