WEED AND SEEDBANK MANAGEMENT WITH INTEGRATED METHODS AS INFLUENCED BY TILLAGE

Abstract

Many growers perceive that reduced herbicide inputs and greater reliance on mechanical methods will result in increased weed management problems over time. Previous research has shown short-term benefits of integrated weed management strategies, but information concerning the long-term implications of these strategies is lacking. Therefore, research was conducted from 1992 through 1995 to determine the influence of full-rate preemergence broadcast, half-rate preemergence broadcast plus cultivation, and full-rate preemergence band plus cultivation treatments on weed population and seedbank dynamics in no-tillage (NT), chisel plow (CP), and moldboard plow (MP) systems in both continuous corn (CC) and corn—soybean (CS) rotation. Seventeen weed species were identified in the plant population and seedbank across all treatments, but common lambsquarters, giant foxtail, and redroot pigweed dominanted. Vertical distribution of weed seeds in soil was influenced by tillage, with 74, 59, and 43% of the total viable seed of these species less than 10 cm deep in NT, CP, and MP, respectively. In contrast, seed dormancy in the spring was not influenced greatly by tillage and averaged 79, 10, and 42% for common lambsquarters, giant foxtail, and redroot pigweed, respectively, across tillage methods. Crop rotation was not a major factor influencing weed population and seedbank dynamics. From 1992 to 1995, reduction of shoot biomass and seed production of the predominant weed species were similar among weed management treatments in most tillage and crop rotation systems. The influence of weed management treatments on the seedbank was also similar, with up to 50, 95, and 92% less seed of common lambsquarters, giant foxtail, and redroot pigweed, respectively, in the seedbank in 1995 than in 1992. Corn and soybean grain yields were similar among weed management treatments and were greater than the nontreated check in each tillage and crop rotation treatment. These results indicate that reduced herbicide inputs plus interrow cultivation were as effective as full-rate herbicide inputs for the management of several annual weed species in both conventional- and conservation-tillage systems over 4 yr.