Fig. 4. Amount of C derived from cowpea residue in nematode biomass C at 31 d; NT = no-till, ST = standard tillage, +Res = residue added, Row = cores taken from plant row, Ctr = cores taken from the bed center, Int = cores taken from an intermediate position between the plant row and the bed center. Statistical differences are expressed with a or b and s or t at 0- to 5- and 5- to 15-cm depths, respectively. The error bars show the standard error.