Production and decay of structural root material of winter wheat and sugar beet in conventional and integrated cropping systems

Production of structural root material of sugarbeet and winter wheat was quantified by analysis of root growth and decay in a time series of minirhizotron images, combined with a single auger sampling in the Netherlands. Cumulative root production of winter wheat was approx equal to 1700 kg/ha for conventional crop management and 1960 kg/ha for integrated (less pesticides and mineral fertilizer, less intensive soil tillage and more organic manure) crop management. At harvest time 85% and 68% (in 1986 and 1990, respectively) of structural root production remained as intact roots in the soil in both management systems. For sugarbeet total fine root production was estimated at 1150 kg/ha in 1987 and 1989, with a significantly lower amount on the field where minimum tillage was implemented in 1986; on average 47% of total root production remained as intact roots at harvest. Winter wheat root decay was studied with litter pots after harvest and in the following growing season. Initially, the N concentration in remaining roots increased while dry weight decreased. No net immobilization or mineralization of N and P during autumn was evident. During the next growing season net mineralization was proportional to loss of root weight in an exponential decay with a half-life of 600 degree days (daily temp. sum). No difference between the two management systems was found