Nutrients, soluble salts, and pathogenic bacteria in feedlot-pen manure have the potential to cause pollution of the environment. A three-year study (1998-2000) was conducted at a beef cattle (Bos taurus) feedlot in southern Alberta, Canada to determine the effect of bedding material [barley (Hordeum vulgare L.) straw versus wood chips] and season on the chemical and bacterial properties of pen-floor manure. Manure was sampled for chemical content (N, P, soluble salts, electrical conductivity, and pH) and populations of four groups of bacteria (Escherichia coli, total coliforms, and total aerobic heterotrophs at 27 and 39 degrees C). More chemical parameters of manure were significantly (P < or = 0.05) affected by season (SO4, Na, Mg, K, Ca, sodium adsorption ratio [SAR], total C, NO3-N, NH4-N, total P, and available P) than by bedding (K, pH, total C, C to N ratio, NH4-N, and available P). Bedding had no significant (P > 0.05) effect on the four bacterial groups whereas season affected all four groups. Numbers of E. coli and total coliforms (TC) were significantly higher by 1.72 to 2.02 log10 units in the summer than the other three seasons, which was consistent with a strong positive correlation of E. coli and TC with air temperature. The low ratio of bedding to manure in the pens was probably the major cause of the lack of significant bedding effects. Bedding material and seasonal timing of cleaning feedlot pens and land application of manure may be a potential tool to manage nutrients, soluble salts, and pathogens in manure.