Acta Agriculturae Slovenica (Sep 1998)
Symbiotic efficiency and storage stability of molasses based liquid inoculant formulations for soybean (Glycine max L., Merr.)
Abstract
Three liquid inoculant formulations (broth culture mixed with molasses, perlite or vermiculite) were tested for the survival of rhizobia on seeds and early nodulation in the field. Two inoculant formulations were used to evaluate the response to inoculation of eleven soybean cultivars in the field. Good survival of rhizobia was observed in broth stored at room temperature (20 - 25o C) over 27 weeks. Initial population of 109 rhizobia/ml declined to 108 rhizobia/ml, as determined by plate counts and MPN assays. Broth inoculant applied to seed with molasses as a sticker, was superior to vermiculite or perlite supplemented inoculant, with respect to survival of rhizobia on seed, whereas perlite supplemented inoculant was the most effective with regard to early nodulation. Agronomically acceptable numbers of viable rhizobia (104 to 106 CFU per seed) were maintained on inoculated seed stored for 4 weeks at room temperature. In 11 soybean cultivars a 119 to 193 % increase in seed yield was observed as a result of inoculation. Although the highest response to inoculation was recorded in cultivars with lowest yield, when uninoculated, this did not compensate for lower response of cultivars with high yield potential. Total plant N analysis indicated that, even at moderate grain yield (about 2400 kg/ha), well nodulated soybean crop fixed about 240 kg N/ha, of which about 170 kg N/ha may be returned to soil with plant residues.
