STAND, YIELD, WEED BIOMASS, AND SURFACE RESIDUE COVER COMPARISONS BETWEEN 3 CROPPING TILLAGE SYSTEMS ON A WELL-DRAINED SILT LOAM SOIL IN OHIO, USA/

Systems research is a departure from traditional, controlled factor ex periments. Whole system experiments provide information about interact ions that affect the success of the system. The objectives of this stu dy were to compare corn (Zea mays L.) and soybean [Glycine max (L.) Me rr.] productivity, surface residue cover after planting, corn plant es tablishment, and weed biomass under three cropping/tillage systems. Th e systems were continuous corn (C/C) (chisel plowed), corn/soybean (C/ S) rotation (no-tillage for corn/chisel plowed for soybeans), and corn /soybean/wheat (Triticum aestivium L.) (C/S/W) rotation (ridge tillage ). All phases of each rotation were established in triplicate on 0.4 h a plots on a Huntington silt loam (fine-silty, mixed, mesic fluventic Hapludoll) soil at Piketon, Ohio, USA. The study was conducted for 5 y ears, from 1991-1995. No differences in yields between systems were de tected, except for the first year soybeans on ridges. The 5-year avera ge corn yield was 7815 kg ha(-1), which was 315 kg ha(-1) above the hi storical regional average. The 5-year average soybean yield was 2969 k g ha(-1) which was 269 kg ha(-1) above the historical regional average . The no-till corn (C/S) had significantly higher residue cover (avera ge of 44.4%) at planting than the other two systems (average of 21.1% for C/C and 33.2% for C/S/W), however all systems had surface residue cover greater than or equal to 30% in at least half of the years studi ed. In the soybean phases the average surface residue was 23.8% in the C/S treatment and 35.8% in the C/S/W treatment. Differences in plant emergence were only detected in 1995 for corn, with the C/C treatment having the highest plant establishment ratio (95.7%). The C/S corn pla nt establishment was 83% and the C/S/W was the lowest at 60%. Note tha t this difference in stand did not result in a detectable difference i n yield. No differences between systems were detected for early season and end of season weed biomasses. Based on 5 years of field data, any of the three cropping/tillage systems can be adopted on a well-draine d silt loam soil without yield reductions in corn or soybean. (C) 1997 Elsevier Science B.V.