Table 2.

Analysis of variance for rates of CH₄ production.

	df	F	P
Site	2	0.37	0.6908
Date	6	51.03	0.0001
Site × date	10	2.07	0.0320
Treatment	3	5.72	0.0011
Treatment × site	6	3.12	0.0070
Treatment × date	16	3.91	0.0001
Site × date × treatment	24	2.51	0.0006

Df, degrees of freedom; F, F ratio; P, probability of significant difference.

Treatment = Control, +Acetate, +rifampicin, and +H₂ + rifampicin.