Partitioning roots for studying cropping systems containing more than one species is important since root growth interaction could influence system performance. The study objective was to test a method for segregating plant species roots from soil samples taken in a mixed stand of corn (Zea mays L.), a C4, and kura clover (Trifolium ambiguum M. Bieb.), a C3 plant. Soil cores containing both corn and kura clover roots were obtained at three distances from the corn row and at two depths in a Rozetta silt loam soil (moderately well drained, fine‐silty, mixed, superactive, mesic Typic Hapludalf). Root composition of these C4 and C3 species was based on 13C/12C ratios expressed as δ13C. A significant linear relationship (r2 = 0.99) was found between the δ13C and the percentage of corn roots in samples containing known ratios of corn and kura clover roots. This relationship was used to determine corn and kura clover root percentages in field samples. Ratios of 13C/12C effectively segregated corn and kura clover root materials obtained from soil samples and seem to be a powerful tool for partitioning roots of C3 and C4 plants in similar studies.

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Introduction Materials and MethodsResults and Discussion 7 Conclusions References Cited V CF[APTER 4. GENERAL CONCLUSIONS APPENDIX A. DATA FOR C~:iAPTER 2 APPENDIX B. DATA FOR C~:[APTER 3 APPENDIX C. ADDITIONAL DATA ACKI~TOWLEDGEMENTS vl for this region should efficiently integrate row crop agriculture with animal production systems.Recent research indicates that row crop production, especially corn, might be made considerably more environmentally friendly with use of a kura clover (Trifolium ambiguum M. Bieb.) living mulch (Albrecht et al., 1999; Zemenchik et al., 2000). The combination of corn and clover fits well with integrated row crop/animal enterprises. This combination should be more environmentally friendly in terms of phosphorus and soil losses than conventional carn production; however, data are missing that could prove or disprove this hypothesis.The general goal of this research is to increase our knowledge regarding soil conservation and interspecies competition with corn-kura clover living mulch systems. This thesis contains three separate chapters. The first contains the general introduction and explanation of the thesis, and is followed by the literature review of the research topic. The second chapter addresses the first study conducted: Corn/kura clover living mulch effects on root growth patterns. The third chapter addresses a second study: Corn/kura clover living mulch effects on soil erosion, water runoff, and phosphorus losses. Chapters two and three are written in manuscript format and will be submitted to peer reviewed journals for publication.