Alternative Approaches to Weed Management

Herbicide technology and use have been the focus of weed management research for the past several decades. Herbicides are an important component of weed management and will remain so for years to come. However, there is increasing pressure to improve the efficiency of herbicide use and develop alternative control methods. Herbicides are used on over 95% of the com and soybean in the Com Belt because of the presence of weeds and the need to minimize their adverse economic impacts. Large inputs of herbicides and tillage are needed to control weeds because of the lack of knowledge of weed biology and ecology, continuous production of summer annual row crops, and the absence of control alternatives. Currently, weed science has few, if any, alternatives to herbicides and tillage that are both economically and environmentally desirable

Tillage Systems and Weed Population Dynamics

Conservation tillage (CT) has had more impact on weed control in row crop production than any other recent change in management practices. In conventional tillage systems, moldboard plowing and secondary tillage just before planting help crop seedlings get an equal start with weed seedlings. In CT systems, herbicides are used to substitute for some or all of this tillage

Initial dates of weed emergence

Timing of weed emergence varies both from year to year and also across the state. The table provides information on the initial date of emergence of five early weed species at locations across Iowa. Giant ragweed, one of the earliest emerging summer annuals found in crop fields, initiated emergence in the last week of March or first week of April in both 1998 and 1999. At most locations giant foxtail began emergence about 4 weeks after giant ragweed, but at the SE (Crawfordsville) location there has been only a 2-week difference in initial emergence of these species

Emergence Patterns of Annual Weeds of Corn and Soybean

A better understanding of weed biology is critical for the development of more efficient weed management systems. Improved information on weed biology will not allow us to eliminate the inputs currently used to manage weeds. However, it provides the foundation for the development of new strategies and more efficient techniques to use these tools, resulting in more reliable weed management systems that are cost-effective and pose less threat to the environment

Relative Emergence of Weeds of Corn and Soybean

The success of integrated weed management relies on matching control strategies to the specific weed problem in a field. This requires information not only on what weed species and how many of these weeds are present in a field, but also knowledge of the distribution of the weeds throughout the field and the stage of development of these weeds. Weed control recommendations typically provide information on appropriate tillage methods and herbicide selection. The information concerning weed infestations used to base these recommendations typically is not of sufficient detail to optimize the efficiency of these strategies

Spring-seeded smother plants for weed control in corn and soybeans

Smother plants are specialized cover crops developed for their ability to suppress weeds and may provide an alternative, non-chemical method of weed control. The goal of this project was to define the characteristics and mechanics of establishing a successful spring-seeded smother plant system and to study and exploit the competitive interactions among weeds, smother plants, and the crop

Soybean Canopy Gap Influence on Velvetleaf Seed Production

Gaps in the soybean row provide locations for velvetleaf (Abutilon theophrasti) plant growth. Gap width, and velvetleaf plant location within the gap, were investigated for effect on seed production. There was no significant difference in velvetleaf capsule production between plants that grew either centered in a gap or at the western end of a gap in east-west oriented soybean rows. Also, there was no difference in plant survival, emergence through the soybean canopy, flowering, locule number per capsule, or average seed weight of velvetleaf based on gap width. However, there was a difference in capsule production based on gap width. In 1999, seed capsule production increased from approximately 35 capsules plant-1 at 0 cm gap width to 140 capsules plant-1 in the 90 cm gap. In 2000, seed capsule production increased from approximately 9 capsules plant-1 at 0 cm gap width to 98 capsules plant-1 in the 90 cm gap. Seed production ranged from an estimate of 300 to 5900 seeds plant-1. As gap width in the soybean row increases, it becomes more important to monitor and control velvetleaf growth. It is even possible, however, to have significant velvetleaf seed production from plants that emerge in a 30 cm gap in the row