Influence of Crop Rotation, Tillage, and Management Inputs on Weed Seed Production

Approaches to crop production that successfully reduce weed seed production can benefit farming systems by reducing management inputs and costs. A 5-yr rotation study was conducted in order to determine the effects that interactions between crop rotation, tillage, and amount of herbicide and fertilizer (management inputs) have on annual grass and broad-leaved weed seed production and fecundity. There were 10 crop rotation and tillage system combinations and three levels of management inputs (high, medium, and low). Green and yellow foxtail were the major weed species, and together they yielded between 76 and 93% of collected weed seeds. From 1990 to 1994, average grass weed seed productions were 7.3 by 103, 3.7 by 103 6.1 by 103 and 5.7 by 103 seeds m−-2, whereas average broad-leaved weed seed productions were 0.4 by 103, 0.4 by 103, 1.4 by 103, and 0.4 by 103 seeds m−-2 in crop rotations using conventional tillage (moldboard plow), conservation tillage, no tillage, and ridge tillage, respectively. Crop rotations using conventional or ridge tillage consistently produced more grass and broad-leaved weed seeds, especially in low-input plots. There was little difference in weed seed production among input levels for crop rotations using conservation tillage. Comparing rotations that began and ended with a corn crop revealed that by increasing crop diversity within a rotation while simultaneously reducing the amount of tillage, significantly fewer grass and broad-leaved weed seeds were produced. Among the rotations, grass and broad-leaved weed fecundity were highly variable, but fecundity declined from 1990 to 1994 within each rotation, with a concomitant increase in grass and broad-leaved weed density over the same period. Crop rotation in combination with reduced tillage is an effective way of limiting grass and broad-leaved weed seed production, regardless of the level of management input applied

Emergence of common lambsquarters (Chenopodium album L.) is influenced by the landscape position in which seeds developed

In a 2-yr field study, we evaluated the emergence and early growth of Chenopodium album L. (common lambsquarters) seedlings as affected by the landscape position in which the seeds (i) developed, (ii) overwintered, and (iii) were planted. Results indicated that a higher proportion of seeds originating from lower slope positions emerged compared with seeds originating from the backslope or upper slope. The timing of emergence was the same for all seed source locations. There was no influence of overwintering location on weed emergence. Regardless of the seed source, we observed faster emergence and growth of C. album planted in the lower slope, where soil conditions were more conducive to growth. These experiments will support the development of new strategies and decision aids to improve weed management

Using Abrasive Grit for Weed Management in Field Crops

Abrasive grit, applied at high pressure and directed at plant base, can control weeds and increase yield. We evaluated fertilizer [pelletized turkey (Meleagris gallopavo) litter] and non-fertilizer [walnut (Juglans regia) shell] grits for maize and soybean in-row (IR) weed management. Grits were applied at V1 and V5 of maize, and V1 and V3 of soybean. Between-row weed cultivation was done alone (BR), or in combination with grit (I/B), after grit application. Small weeds (<4 cm) were controlled after grit treatment, but, larger broadleaf weeds, grass weeds (treated when growing points were below ground), and later emerging weeds resulted in IR weed biomass similar between season-long weedy (SLW) and IR treatments by August. In maize, fertilizer and nonfertilizer I/B treatments averaged 44 and 14% greater yields, respectively, than SLW (p<0.01) but each was similar to BR which averaged 23% greater yield (p=0.63). Maize grain had 16% higher N content in the fertilizer I/B treatment than SLW or nonfertilizer I/B (p<0.003). In soybean, I/B increased yield by 17% (p=0.009) over SLW yield, but was similar to the BR increase of 22% (p=0.13). Maize had a greater positive response to fertilizer than nonfertilizer grit, whereas soybean was less influenced by I/B treatment

Air-propelled Abrasive Grit can Damage the Perennial Weed Quackgrass

our field experiments were conducted during 2016 and 2017 to evaluate the efficacy of preemergence herbicides to control glyphosate-resistant common ragweed in corn. Dicamba, dicamba/atrazine, mesotrione + atrazine, isoxaflutole + atrazine, saflufenacil/dimethenamid-P, and S-metolachlor/mesotrione/bicyclopyrone/atrazine were the most efficacious herbicides, providing 94%–100% control of GR common ragweed and reducing density and biomass 98%–100%

Relative Emergence of Weeds and 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. Information on weed populations can be improved by increasing the time spent scouting fields. However, time restraints during the busy spring season restrict this opportunity. This problem could be alleviated with an improved understanding of the environmental influences on weed emergence and growth, therefore allowing us to predict when best to invest time in scouting. Armed with greater knowledge of weed development and populations, a person could determine the optimum time for tillage and crop planting to reduce weed populations, maximizing the effectiveness of mechanical weed control operations, and for timing of burndown and postemergence herbicide applications. Although there has been considerable research and modeling of weed emergence in recent years, little effort has been directed toward development of emergence information for persons involved in weed management. This paper provides information on how weed emergence timing influences weed management systems. Included are preliminary rankings of relative emergence for important weed species in the Midwest. The Leopold Center for Sustainable Agriculture is supporting efforts to develop more precise emergence indices that will be of greater benefit in aiding the development of more efficient weed management systems

Abrasive grit-weeding in apple

New forms of weed control may be useful in apple orchards. Abrasive corn cob grit applied under high air pressure was tested for the control of weeds in an established apple orchard over two years. Additionally, efficacy of abrasive grit-weeding was compared to that of hand-weeding. As expected, hand-weeding nearly eliminated all weeds. In contrast, grit-weeding achieved about 90% control of broadleaf weeds, only 15% control of grass weeds, and 70 to 80% control of all weeds. Much of the time and amount of grit used was devoted to suppressing grass weeds. Relatively soft corn cob grit easily abraded and controlled broadleaf weeds. However, harder and more angular grit materials may be needed to control annual and perennial grasses

Cuphea Yields in Iowa, 2002

Cuphea is a potential source of lauric and capric acids, which are medium-chain-length fatty acids. They are used to manufacture various products such as detergents (lauric) and high quality lubricants (capric). The fatty acids are contained in oils that are produced and stored in cuphea seeds. Currently, all of the lauric acid used for detergents is derived from imported palm and coconut oils. There is no domestic source of this fatty acid, which is a dilemma that U.S. industries, such as Proctor & Gamble and ADM, would like to resolve