Effect of Repeated Inoculation with Increasing Inoculum Rates of Bradyrhizobium japonicum on Biological Nitrogen Fixation of Soybean

Mussaddak Janat*(1) Mohsen Makhlouf(1) and Muhhamad Manhal Alzoubi(2)

(1). Department of Agriculture, Atomic Energy Commission of Syria.
(2). Natural Resources Research Administration, General Commission for Scientific Agricultural Research (GCSAR), Damascus, Syria.

(*Corresponding author: Dr. Mussaddak Janat. E-Mail: ascientific@aec.org.sy).

  Received: 07/01/ 2016                                   Accepted: 01/03/ 2016


Introducing effective Bradyrhizobium japonicum liquid inoculum for inoculation of soybean seeds is an effective and efficient way for introducing the specific rhizobia to the soil and consequently to the rhizosphere of the soybean. The efficacy of inoculation of soybean varies depending on several factors, such as; inefficient or very low density of B. japonicum or any other uncompetitive indigenous bradyrhizobial strain if any, soil temperature, depth of application, specific stain, poor soybean root infection, number of viable rhizobia, and time of application. Therefore, field experiment was carried out for three consecutive years (2007–2009) to assess the efficacy of repeated inoculation of soybean with liquid inoculant at different growth stages, the effect of repeated cultivation and increasing number of rhizobia per injection on good infection of soybean roots, consequently the amount of N2fixed by soybean  were determined. Treatments consisted of four different liquid inoculum of Bradyrhizobium japonicum at a rate of 5×108 cells/ ml per injection repeated two, three, and four times, then compared to the control without inoculation. Results showed that the first injection through the drip irrigation system was enough to ensure good infection, still two, three and four injection did not negatively affect the infection and the amount of N2 fixed but in some cases improved the efficacy of inoculation.

Key words: Fertigation, Water Productivity, Soil nitrogen, Nitrogen derived from atmosphere.

Full paper in English