Temporal and soil depth-related variation in soil enzyme activities and in root growth of red clover (Trifolium pratense) and timothy (Phleum pratense) in the field

Activities of 12 different enzymes in soil and growth of timothy (Phleum pratense) and red clover (Trifolium pratense) roots were monitored on fine sand soil (Aquic Haplocryoll) throughout the third growing season of the plants. Both root biomass and enzyme activities decreased with increasing soil depth. The root biomass depended on the plant, the soil depth and the date within the growing season. The steepness of the depth gradient varied between activities of different enzymes and the seasonal pattern was also enzyme-dependent. Correlations between enzyme activities were highest in subsoil samples from 30 to 40 cm depth and in these samples soil organic matter and enzyme activities were intercorrelated. Plant root impact was less pronounced and only a few enzyme activities were higher in red clover than in timothy soil.