Crop residue treatments Quantity of residue (g) Clay pot1 Micro-plot2 Coarse-ground corn kernels (CK) 13 100 Corn roots 10 10,000 Corn stalks (CS) 7 10,000 No residue added 0 0 Coarse-ground soybean kernels (SK) 10.5 100 Soybean stalks (SS) 10 5000 Soybean roots 10 5000 CS spread on the soil surface3 7 5000 CK and CS spread on the soil surface3 13 and 7 100 and 5000

Table 1: Crop residue treatments for the greenhouse and micro-plots. 1Crop residues were mixed with soil and inoculated with spore suspension of Fusarium virguliforme, a single-spore Iowa isolate Fsg-ISU 1 (1 × 105 conidia per gram of soil) in greenhouse studies . 2Crop residue was spread on micro-plots and inoculated with 25 g steam-sterilized white sorghum grain colonized by Fsg-ISU 1 and tilled. 3Crop residue was spread on micro-plots and inoculated with 25 g steam-sterilized white sorghum grain colonized by Fsg-ISU 1 and micro-plots remained untilled.