Laboratory testing for numbers of viable rhizobia on commercially-pelleted legume seed

Abstract

Abstract As part of a quality evaluation program commercially-pelleted legume seed was sampled over a 3 year period and tested for numbers of viable rhizobia. Tests were carried out 7–10 days after manufacture during the first year, but in succeeding years samples were tested 28 days after manufacture after storage at 19–22°C. Manufacturers generally differed in the average number of rhizobia per seed attained with a given species and this number could fluctuate abruptly. With individual manufacturers there were consistent differences among species in the average number of rhizobia per seed. There were also differences among manufacturers and among species in the percentage of rhizobia surviving a 21-day storage period, indicating the importance of assessing numbers under conditions representative of those experienced under practical conditions. The numbers of viable rhizobia found on some of the samples tested were so low (< 10/seed) as to entail a high risk of inoculation failure if the seed was sown in...