YIELD AND NITROGEN-FIXATION OF CHICKPEA CULTIVARS IN RESPONSE TO INOCULATION WITH SELECTED RHIZOBIAL STRAINS

With development of new cultivars for winter sowing, production of Kabuli chickpea (Cicer arietinum L.) has expanded into drier areas of the Mediterranean region where low or less effective populations of indigenous rhizobia may limit N2 fixation. This study was conducted to quantify field N2 fixation using N-15 for eight chickpea cultivars as affected by native rhizobial populations and three introduced rhizobial strains, and to determine the extent of strain-cultivar interactions for N2 fixation and yield. Host-by-strain interactions for N2 fixation were highly significant in a greenhouse experiment utilizing a N-free aseptic hydroponic system. Inoculation significantly increased total above ground dry matter (AGDM) and seed yields over uninoculated control in field trials conducted at two locations at Tel Hadya, Syria, on a Vertic Chromoxeralf soil during two seasons (1987-1989). All yield and N2 fixation parameters differed significantly among chickpea cultivars and rhizobial strains in the wetter (1987-1988) season where cultivar-strain interactions were significant for seed yield, N yield, and N2 fixation; differences in N yield and N2 fixation were not significant in the drier season. Average quantities of N2 fixed were 68 and 27 kg N ha-1 in inoculated treatments for 1987-1988 and 1988-1989 trials, respectively. Inoculation with the best strain treatment in 1987-1988 increased the average proportion of N derived from fixation (%Ndfa) from 52% to 72%; maximum %Ndfa for this trial was 81%. Maximum %Ndfa was 67% in the 1988-1989 trial. Significant strain-by-cultivar interactions and the yield response to selected rhizobial strains suggest an important role for field inoculation of chickpea for increased N2 fixation.