Estimate of N2-fixation in waste-derived compost after treatment with glucose

It has been shown previously that treatment of grass swards cultured in waste-derived compost and treated with 8-24 g (5-15 g.L-1) glucose over 8 weeks resulted in a substantial increase of shoot dry mailer and total nitrogen content, while a growth inhibiting effect was observed in unamended field soil. The improved sward performance in compost was associated with a significant expansion of the aerobic, diazotrophic bacterial population in the growth medium. The purpose of the present experiment was to measure the contribution of N-2-fixation to the improved growth. Glucose treatment resulted in the fixation of at least 128 mg total nitrogen per pat (equivalent to 14.5 mg N fixed per g C respired; 104 kg.ha(-1)), with 32 % made available to shoots for growth over the following 6 months. There was no evidence of accelerated soil organic matter decomposition that could account for the increased N availability. (C) 1999 Editions scientifiques et medicales Elsevier SAS.