Impact of the rhizosphere on soil microarthropods in agroecosystems on theGeorgia piedmont

We pulse-labeled corn (Zea mays) and weed plants with photosynthetically fi xed Carbon-14 to investigate the importance of the rhizosphere as a food so urce for soil microarthropod food webs. In field samples, we followed the m ovement of C-14 from plant shoots to roots to microarthropods. In conventio nally tilled (CT) agroecosystems, the soil microarthropods accumulated radi oactive tracer and reached concentrations as high as those in roots. In no- tillage (NT) agroecosystems, radioisotope concentrations in microarthropods were not as high. The CT systems lack surface organic litter, an alternate food base for microarthropods. Results suggest that feeding in the rhizosp here is more important in CT systems. Weeds transferred higher concentratio ns of tracer into the rhizosphere than did crop plants, suggesting that wee ds in CT systems may be important in fueling food webs, (C) 2001 Elsevier S cience B.V. All rights reserved.