Developing a slow-release nitrogen fertilizer from organic sources: III Isolation and action of a feather-degrading actinomycete

Abstract

An actinomycete designated Streptomyces cn1 with a high proteolytic activity and capacity to degrade feather keratin was isolated and its effectiveness for altering feathers to yield a slow-release N fertilizer was evaluated. The pattern of N release in column elution tests from feathers ground to a particle size ≤1 mm, but otherwise unaltered, was characterized by a first period of release from weeks 2 through 5 with a high peak at week 3 and a second period of release from 14 to 20 weeks. The release of N during the first period was 10.5% and during the second period it was 7.3% for a total of only 17.8% of the N contained in these feathers. Grinding feathers to a finer particle size ≤0.5 mm caused increases in N release during the two periods to 14.7% and 15.8% N, respectively, for a total of 30.5% and second period N release began 5 weeks earlier at week 9. Microbial hydrolysis with Streptomyces cn1 for 1 though 5 days resulted in an adverse reduction in total N released, due in part to drying of feathers after hydrolysis. Hydrolysis of feathers for 7 days resulted in 42.6% of total N released over 20 weeks with 77.0% of this released during weeks 6 through 20. The second period of release began at week 8. Hydrolysis of feathers for 9 days was best for purposes of a slow-release fertilizer. Forty five percent of total N was released over 20 weeks with 89.3% of this released during the second period that began in week 7. Root substrate pH was increased in all treatments where feathers were applied. This would require a reduction in the rate of limestone incorporated into a commercial substrate when feather N is used. Pepsin digestibility and ninhydrin tests provided some insight into the N release mechanism but did not effectively predict N release from the feather products.