A field experiment has been conducted during the spring season of 2013-2014 at a private field in Al-Qurna county in clay loam soil with E.C interaction 3.2 ds.m-1 to study the effect of interference between bio-fertilizer (Azotobacter chroococcum) and two types of sorghum (Sorghum bicolor).
The experiment is carried out by using three levels of bio-fertilizer {no vaccine, treatment first strain of Azotobacter (A1), and the second strain of Azotobacter (A2)}and the two types of sorghum local variety (Kafair) and the American hybrid ( NK8817). the experiment is designed by R.C.B.D. in a split plot design in three replicates, bio-fertilizer are in the main plots ,while the sorghum varieties are in the sub.plots.
The results show that application of Azotobacter chroococcum bacteria cause significantly and increase in the seeds number per head, weight of 1000 grain , plant yield, grain yield, percentage of protein and protein yield , with no significant difference between Azotobacter A1 of Azotobacter A2 It gives grain yield reached to ( 3908.9 and 4030.7 ton h-1 ) respectively.
The result also show that there are significant differences between the two cultivated varieties, variety Kafair is superior with protein yield while NK8817 variety is superior with seeds number per head , weight of 1000 seeds ,plant yield and grain yield and percentage protein and it gives grain yield reached to 3831.8 ton h-1 .
There is a significant interaction between bio-fertilizer and Cultivated varieties, the NK8817 variety which is treated with the second strain of Azotobacter A2 gives high grain yield reached to 4431.4 ton h-1.