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Management in a modified no-tillage corn–soybean–wheat rotation influences weed population and community dynamics
- Clarence J. Swanton, Barbara D. Booth, Kevin Chandler, David R. Clements, Anil Shrestha
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- Journal:
- Weed Science / Volume 54 / Issue 1 / February 2006
- Published online by Cambridge University Press:
- 20 January 2017, pp. 47-58
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Conservation tillage systems, such as no-tillage, are ecologically advantageous because they reduce soil erosion; however, they rely heavily on herbicide use. Our goal was to determine how weed communities of no-tillage systems are affected when the system is modified to reduce herbicide use through a combination of banded herbicides and interrow cultivation. To this end, we conducted a 9-yr study in a no-tillage corn–soybean–winter wheat rotation. All management systems had a preplant application of glyphosate, followed by either broadcast PRE herbicides (conventional no-tillage), interrow cultivation with banded PRE herbicides, or interrow cultivation alone. Aboveground weed densities were assessed each year and data were grouped into early (1991 to 1993) and late (1996 to 1998) time periods. Over time, weed communities became more distinct, showing a strong response to management and crop. In the early years, weed communities separated more in response to management than crop. In the late years, this was reversed. Weed communities in systems with interrow cultivation were more diverse than those in conventional no-tillage. The response to weed management system and crop was species specific. For example, the abundance of yellow foxtail was higher when interrow cultivation was employed, but abundance was equal in all crops. Dandelion was more abundant in conventional no-tillage of corn and soybean; however, it was equally abundant in all management systems in wheat. Seed bank species richness increased over time and was highest in systems with interrow cultivation. Herbicide use can be reduced in a modified no-tillage corn–soybean–wheat rotation by incorporating interrow cultivation, with or without banded herbicides, into the management plan. The weed community trajectory changes, and the weed community becomes more diverse. A more diverse weed community will not necessarily alter how we manage weeds.
Evaluation of alternative weed management systems in a modified no-tillage corn–soybean–winter wheat rotation: weed densities, crop yield, and economics
- Clarence J. Swanton, Anil Shrestha, David R. Clements, Barbara D. Booth, Kevin Chandler
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- Journal:
- Weed Science / Volume 50 / Issue 4 / August 2002
- Published online by Cambridge University Press:
- 20 January 2017, pp. 504-511
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A 9-yr (1990–1998) study was conducted at Woodstock, ON, Canada, to evaluate weed densities, crop yields, and gross returns in a modified no-tillage (no primary tillage) corn–soybean–winter wheat rotation under three weed management treatments: (1) minimum, preplant application of glyphosate followed by mechanical control; (2) integrated weed management (IWM), preplant application of glyphosate followed by band application of preemergence herbicides plus mechanical control; and (3) conventional, preplant application of glyphosate followed by broadcast application of preemergence herbicides in corn and soybean. In wheat the minimum and IWM treatments had no additional weed control measures other than the preplant application of glyphosate, whereas the conventional treatment had a broadcast application of a postemergence herbicide. Weed densities were assessed each year, (except in 1990) once during the growing season in corn and soybean and immediately after crop harvest in wheat. Adjusted gross return was calculated as the gross revenue minus the unique costs for weed control for each of the treatments. Weed densities were greater in the minimum treatment compared with the IWM or conventional treatment in all crops. Weed densities in the IWM and conventional treatments did not differ. There was no apparent “buildup” of weed density with time in the rotation resulting from weed escapes. Hence, these data challenge current thinking that weed densities increase with time if weed escapes are allowed to go to seed. Corn and soybean yields in the IWM and conventional treatments did not differ. However, the minimum treatment had the lowest corn and soybean yields. Winter wheat yield was not affected by the treatments. All weed management treatments provided similar gross returns for each crop and for the rotation. Thus, the minimum treatment consisting of glyphosate applied preplant followed by shallow interrow tillage appeared to be a viable option, especially if practiced in a farming system capable of ensuring adequate timing of cultivation operations.
Soil fertility and crop yields in long-term organic and conventional cropping systems in Eastern Nebraska
- Sam E. Wortman, Tomie D. Galusha, Stephen C. Mason, Charles A. Francis
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- Journal:
- Renewable Agriculture and Food Systems / Volume 27 / Issue 3 / September 2012
- Published online by Cambridge University Press:
- 22 July 2011, pp. 200-216
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Organic agriculture aims to build soil quality and provide long-term benefits to people and the environment; however, organic practices may reduce crop yields. This long-term study near Mead, NE was conducted to determine differences in soil fertility and crop yields among conventional and organic cropping systems between 1996 and 2007. The conventional system (CR) consisted of corn (Zea mays L.) or sorghum (Sorghum bicolor (L.) Moench)–soybean (Glycine max (L.) Merr.)–sorghum or corn–soybean, whereas the diversified conventional system (DIR) consisted of corn or sorghum–sorghum or corn–soybean–winter wheat (wheat, Triticum aestivum L.). The animal manure-based organic system (OAM) consisted of soybean–corn or sorghum–soybean–wheat, while the forage-based organic system (OFG) consisted of alfalfa (Medicago sativa L.)–alfalfa–corn or sorghum–wheat. Averaged across sampling years, soil organic matter content (OMC), P, pH, Ca, K, Mg and Zn in the top 15 cm of soil were greatest in the OAM system. However, by 2008 OMC was not different between the two organic systems despite almost two times greater carbon inputs in the OAM system. Corn, sorghum and soybean average annual yields were greatest in either of the two conventional systems (7.65, 6.36 and 2.60 Mg ha−1, respectively), whereas wheat yields were greatest in the OAM system (3.07 Mg ha−1). Relative to the mean of the conventional systems, corn yields were reduced by 13 and 33% in the OAM and OFG systems, respectively. Similarly, sorghum yields in the OAM and OFG systems were reduced by 16 and 27%, respectively. Soybean yields were 20% greater in the conventional systems compared with the OAM system. However, wheat yields were 10% greater in the OAM system compared with the conventional DIR system and 23% greater than yield in the OFG system. Alfalfa in the OFG system yielded an average of 7.41 Mg ha−1 annually. Competitive yields of organic wheat and alfalfa along with the soil fertility benefits associated with animal manure and perennial forage suggest that aspects of the two organic systems be combined to maximize the productivity and sustainability of organic cropping systems.
Increased weed diversity, density and above-ground biomass in long-term organic crop rotations
- Sam E. Wortman, John L. Lindquist, Milton J. Haar, Charles A. Francis
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- Journal:
- Renewable Agriculture and Food Systems / Volume 25 / Issue 4 / December 2010
- Published online by Cambridge University Press:
- 18 June 2010, pp. 281-295
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While weed management is consistently a top priority among farmers, there is also growing concern for the conservation of biodiversity. Maintaining diverse weed communities below bioeconomic thresholds may provide ecosystem services for the crop and the surrounding ecosystem. This study was conducted to determine if weed diversity, density and biomass differ within and among organic and conventional crop rotations. In 2007 and 2008, we sampled weed communities in four long-term crop rotations near Mead, Nebraska using seedbank analyses (elutriation and greenhouse emergence) and above-ground biomass sampling. Two conventional crop rotations consisted of a corn (Zea mays) or sorghum (Sorghum bicolor)–soybean (Glycine max)–sorghum or corn–soybean sequence and a diversified corn or sorghum–sorghum or corn–soybean–wheat (Triticum aestivum) sequence. Two organic rotations consisted of an animal manure-based soybean–corn or sorghum–soybean–wheat sequence and a green manure-based alfalfa (Medicago sativa)–alfalfa–corn or sorghum–wheat sequence. Species diversity of the weed seedbank and the above-ground weed community, as determined by the Shannon diversity index, were greatest in the organic green manure rotation. Averaged across all sampling methods and years, the weed diversity index of the organic green manure rotation was 1.07, followed by the organic animal manure (0.78), diversified conventional (0.76) and conventional (0.66) rotations. The broadleaf weed seedbank density in the tillage layer of the organic animal manure rotation was 1.4×, 3.1× and 5.1× greater than the organic green manure, diversified conventional and conventional rotations, respectively. The grass weed seedbank density in the tillage layer of the organic green manure rotation was 2.0×, 6.1× and 6.4× greater than the organic animal manure, diversified conventional and conventional rotations, respectively. The above-ground weed biomass was generally greatest in the organic rotations. The broadleaf weed biomass in sorghum and wheat did not differ between organic and conventional rotations (CRs), but grass weed biomass was greater in organic compared to CRs for all crops. The above-ground weed biomass did not differ within CRs, and within organic rotations the grass weed biomass was generally greatest in the organic green manure rotation. The weed seedbank and above-ground weed communities that have accumulated in these rotations throughout the experiment suggest a need for greater management in long-term organic rotations that primarily include annual crops. However, results suggest that including a perennial forage crop in organic rotations may reduce broadleaf weed seedbank populations and increase weed diversity.