Urease activity in soil amended with methane-generator sludge: Fid-Bau Portal

Urease activity in soil amended with methane-generator sludge

Atalay, A. / Blanchar, R.W.

AbstractSludge obtained from a methane-generator unit charged with fescue hay Festuca arundinacea Schreb) was air-dried and mixed with a sample from the surface horizon (0–15 cm) of a Menfro silt loam soil (fine-silty, mixed, mesic, Typic Hapludalf) to give 0, 40, and 80 g kg⁻¹ sludge by weight. The sludge-soil mixtures were assayed for urease activity, then used in CO2-evolution or plant-growth studies and again assayed for urease activity. Urease activity was not altered by the addition of sludge when measured 1 h after addition. Urease activity in soil-sludge mixtures upon which plants had been grown for 42 days at − 33 kPa water potential and 25°C, was increased by sludge addition. Urease activity measured in soil-sludge mixtures incubated at − 20 kPa water potential and 25°C was increased significantly (P < 0·05) with increasing sludge. The maximum velocity (Vmax) for urea hydrolysis varied from about 5 to 40 μg N g⁻¹ h⁻¹ and the Km values from 0·7 to 1·mm in the 0 and 80 g kg⁻¹ sludge treatments, respectively. Urease activation energies ranged from 25 to 38 kJ mol⁻¹ in the 20–50°C temperature range and were not altered by sludge addition. During the 106 days of incubation, nearly 15% of the carbon added with the sludge evolved as carbon dioxide.