Field-scale watershed evaluations on deep-loess soils: I. Topography and agronomic practices

Long-term field-scale watershed studies are needed to quantify productivity and environmental imparts of various farming practices. The objective for this study was to summarize geologic, topographic, and agronomic data for f our deep-loess, field-scale watersheds in western Iowa. Average corn grain yield for 1972 through 1995 on Monona (fine-silty, mixed mesic Typic Haplud olls), Ida-Dow (fine-silty, mixed mesic Typic Udorthents), and Napier-Kenne bec (fine-silty, mixed mesic Cumulic Hapludolls) soils was 7.2, 6.7, and 7. 9 Mg ha(-1) (115, 107, and 126 bu/ac), respectively. After more than 20 yr of continuous corn production, the weed community had reached a high densit y and was dominated by foxtail (Setaria) species. It is recommended that fi xture soil and crop management practices on these watershed should focus on increasing crop diversity to control weeds and reduce the apparent yield p enalty associated with continuous corn. The management practices dire shoul d strive to develop a soil rendition that is resilient and able to buffer p eriodic, but anticipated plant water and heat stress.