Survival and efficiency of cowpea rhizobia on pelleted and non-pelleted peanut seeds, treated with fungicides.

Peanut seeds were either normally inoculated with the legume inoculant Okadin, containing cowpea rhizobia, or pelleted and treated with each of the fungicides Brassical, Thiram, Orthocide 75, Falisan, Vitavax 75, and Agrosan. The seeds were then incubated at room (+/- 25 degrees C) or refrigeration temperatures (+/- 5 degrees C). Survival tests were made after 2 and 10 days. Treated seeds were also planted in pots containing Nile silt for testing the efficiency of rhizobia as affected by the fungicide and the pelleting treatments. Pelleting of peanut seeds enhanced the survival of rhizobia whether seeds were incubated at room or refrigeration temperature. Protection was more pronounced when seeds were kept at low temperature. This was true of the fungicides Brassical, Orthocide 75, Vitavax 75, Thiram, and Agrosan. Falisan, however, did not help the rhizobia to survive. All the fungicides tested reduced the number of rhizobia to nil within 10 days when the seeds were normally inoculated and then treated and incubated at room temperature. The numbers of rhizobia were appreciably reduced when incubated at refrigeration temperature. Pelleting tended to prevent the harmful effect of the fungicides. This was clearly demonstrated with a tendency of an increase in the total nitrogen of the plants. On the contrary, normally inoculated and treated seeds grew into plants with reduced amounts of total nitrogen fixed.