Influence of Adhesives and Time Lag Between Seed Treatment and Sowing on Survival of Rhizobia and Crop Response to Inoculation

Abstract

Seed bacterisation is a common practice. Rice kanji is advocated to coat seeds with biofertilizers. Compared to water, rice kanji showed ten fold increase in the number of rhizobial cells adhering to red gram seed. Among the five adhesives tested for survival of inoculated rhizobia on red gram seed surface, gum arabic (40%) was the best followed by jaggery (25%). carboxymethylcellulose (1.5%), rice kanji and water. With rice kanji as adhesive on cowpea seed the inoculum load of 1.4 x 10 rhizobial cells per seed decreased to 2.2 x 10 cells after 1 h. There was no significant difference among the number of rhizobia on inoculated seeds between the time lag of 1 and 24 h. In unsterilised soil, compared to uninoculated control, significantly higher nodule dry weight and plant dry weight were observed with cowpea plants raised immediately after seed bacterisation. Nodule dry weight and plant dry weight of plants raised after a time lag of 1 to 24 h after seed inoculation were found to be on par with those of uninoculated control. Thus the crop response to rhizobial inoculation could be realised in unsterilised soil with a inoculum of 10 cells per seed but not with 102 cells per seed.