Progress 08/01/02 to 05/01/07
Outputs
Crop rotations are a key component of organic cropping systems. A four-year rotation of soybean, oat/alfalfa, alfalfa, and corn consistently resulted in higher corn grain yield and higher net return than a two-year rotation of soybean and corn. Soybean yield was similar for the two rotations. Increasing ground cover (hairy vetch cover crop), or adding organic matter via composted manure had no consistent effect on corn or soybean yields compared to control treatments of no cover crop and uncomposted manure. Hairy vetch was challenging to establish following harvest of corn in October. Giant foxtail and broadleaf weed populations were greater in corn grown in a two-year than a four-year rotation but were not affected by tillage, manure, or cover crop treatments. Broadleaf weed and foxtail populations in soybean were not affected by rotation or other treatments. Soil quality factors were affected by crop rotations. Total organic C and N were greater with the four-year
rotation than for the two-year rotation because of the presence of alfalfa, a perennial crop, in the rotation. A hairy vetch cover crop and composted manure increased potentially mineralizable C, aggregate size, and Bray P compared to the no hairy vetch and uncomposted manure. Canada thistle is a problematic weed in organic cropping systems where synthetic herbicides cannot be used. Repeated tillage can reduce Canada thistle populations in organic cropping systems but tillage destroys soil organic matter and soil quality. Smother cropping with pearl millet, buckwheat, or a pea-buckwheat double crop suppressed Canada thistle populations by competing for resources but their effect was only temporary. Multiple harvests of alfalfa that is maintained for several years is effective in reducing Canada thistle root reserves and populations. Cover crops like winter rye and hairy vetch have potential to increase soil quality and reduce weeds if successfully established in corn. There were no
consistent effects June, August, and October seeding dates on establishment of annual ryegrass-red clover and hairy vetch-winter rye cover crops in corn. Fall cover crop populations were influenced by the occurrence of precipitation following seeding and less by date. Only the August and October planting dates consistently resulted in significant winter and spring biomass. Spring biomass and ground cover were greater for the winter rye-hairy vetch mixture than for the annual ryegrass-red clover mixture. Cover crops had no effect on yield of a subsequent soybean crop. Winter rye provided suppression of broadleaf and grassy weeds. Hairy vetch is frequently used as a cover crop. Farmer landraces and marketed seed of hairy vetch were evaluated for winter cover and persistence. Locally produced landraces had the best persistence and fall cover. Some hairy vetch seed produced outside the Midwest failed to persist in Minnesota. Field research on organic production practices that is conducted
on-farm and on university experiment stations can be used effectively to conduct educational events for farmers and consultants and to conduct training schools for professionals
Impacts
This research was conducted at a long-term organic research site in a low rainfall region of Minnesota. It substantiates the biological and economic value of diversified crop rotations for sustainable organic crop production. Short duration rotations with only corn and soybean production are detrimental to soil health and be difficult in maintaining crop yields even with a cover crop. This should alert policy makers that inclusion of a perennial crop like alfalfa in organic crop rotations is critical for weed control and soil maintenance. The challenge for growers is how to achieve an economic return from alfalfa forage production. Many growers in southwestern Minnesota don't have animals to utilize harvested alfalfa. This research shows challenges of seeding cover crops in regions that lack summer and fall rainfall. Cover crop seeding may cause an economic loss if covers are not successfully established. It shows that seed of hairy vetch cover crops should be produced
in the region of intended use. If not, hairy vetch may not over winter and be available for the following spring. It shows that smother crops like peas or millets provide short-term suppression of Canada thistle. Perennial crops that can be frequently harvested provide the best long term control. Learning groups of farmers, researchers, and educators have been developed to promote transfer of information about organic agriculture production practices. They meet periodically to facilitate discussion and exchange ideas. The learning groups will be a focal point in generating new organic agriculture research.
Publications
- Evans, E., P. Porter, E. Dyck, P. Nickel, C. Sheaffer, D. Wyse, D. Allan and M. harbor. 2003. An update on organic research and outreach at the University of Minnesota's Southwest Research and Outreach Center. Agron. Abst. P. 3003.
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Progress 01/01/06 to 12/31/06
Outputs
In long-term organic cropping system research, we continued to find that crop rotation had a significant affect on corn yields. A four-year rotation of soybean, oat/alfalfa, alfalfa, and corn averaged 20% higher corn yield than a two-year rotation of soybean and corn. Soybean yield was similar for the two rotations. Sowing of a hairy vetch cover crop, use of composted manure to add N, and spring tillage had no consistent effect on corn or soybean yields compared to a control treatment of no cover crop, heap manure, and fall tillage. Populations of giant foxtail, the predominant annual weed at the site, were greater in corn grown in a four year than a two year rotation but were not affected by tillage, manure or cover crop treatments. Foxtail populations in soybean were not affected by rotation, tillage, or manure treatments. Soil quality factors were affected by cropping system treatment effects. Total organic C and N were greater with the four year rotation than for
the 2 year rotation but aggregate size and Bray P were greater with the two year than four year rotation. Using a hairy vetch cover crop and applying composted manure increased potentially mineralizable C, aggregate size, and Bray P compared to the control. For effective Canada thistle control in organic cropping systems, alfalfa should be included in the rotation. Multiple harvests of alfalfa are effective in reducing Canada thistle root reserves and populations. In a rotation that includes only corn and soybean, thistle control via tillage is difficult. Repeated tillage in a fallow year or use of a pea-buckwheat double smother crop are approaches to partially suppress thistle. We evaluated the effect of date of seeding on establishment of cover crops. For annual ryegrass, red clover, and hairy vetch, August planting resulted in greater fall populations than planting in June or October. Winter rye populations were not affected by establishment date. Winter rye and hairy vetch
provided greater coverage than annual ryegrass and red clover. Cover crops had no effect on yield of a subsequent soybean crop. Winter rye provided suppression of broadleaf and grassy weeds.
Impacts
Organic food is the fastest growing sector of the retail market. This research provides new information to producers on practices to increase the efficiency of organic crop production that provides organic food.
Publications
- No publications reported this period
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Progress 01/01/05 to 12/31/05
Outputs
Crop rotation is the most effective weed and soil fertility management tool available to organic farmers. We compared a two-year corn-soybean rotation with a four-year corn-soybean-oat-alfalfa rotation. Giant foxtail and broadleaf population and biomass were greater in corn in the two-year rotation than in the four-year rotation. Within each rotation, a winter rye cover crop after corn and a red clover/hairy vetch cover crop after soybean resulted in greater giant foxtail and broadleaf populations than when no cover crop was seeded following corn. Giant foxtail and broadleaf weed populations were affected by the interaction of crop rotation and cropping system so that the system effect was greater in the two-year rotation than the four-year rotation. Corn grain yield was greater in the four-year rotation compared to the two-year rotation. Corn yield was also greater when fertilized with heap (raw) manure and fall tilled than when grown with a winter rye cover crop.
Soybean yield was not consistently affected by rotation or management system. Corn response to rotation and manure application was due to a greater dependence on nitrogen fertility input than soybean, a crop that has dinitrogen fixation potential. Fall cover crops can reduce soil erosion, increase weed seed predation, and upon incorporation the following spring increase soil biomass and nitrogen recruitment. Interseeding cover crops with corn during the growing season may permit cover crops to establish during the summer and resume growth once corn is removed. Winter rye establishment was best in October and least in June. Red clover establishment was greater in June than in October. Winter rye establishment was greater in June and October than in August. Establishment of hairy vetch was greater in October than in June or August. Winter rye was the greatest spring biomass producer among the cover crops. In contrast, red clover and ryegrass did not overwinter and produce spring
biomass. Hairy vetch biomass production in the spring was dependent on winter conditions because it overwintered in only one of two years. Populations of weeds and yields in a following soybean crop were not consistently affected by cover crop treatments. Canada thistle is a problematic weed for certified organic producers who eschew systemic herbicides and must use multiple-year management strategies for its control. Repeated tillage from May through September was the most effective control for Canada thistle in organic systems. Growth of smother crops such as pea, buckwheat, millet, and sun hemp resulted in fewer Canada thistles relative to growth of corn with between row tillage. Systems that include smother crops such as a pea-buckwheat double crop and cultivated soybean production may allow simultaneous crop production and effective management of Canada thistle. Results generated from this research were used in educational activities and professional presentations. These included
field schools, demonstrations, and field days.
Impacts
We have identified alternative approaches to control weeds, maintain environmental quality, and maintain crop yields in organic systems. Alternative approaches are essential for economic survival of organic farmers.
Publications
- Harbur, M.M., D.L. Wyse, C.C. Sheaffer and D.L. Allan. 2005. Canada thistle management in organic field crops. Proc. of the North Central Weed Science Society, December 12-16, 2005, Kansas City, MO.
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Progress 01/01/04 to 12/31/04
Outputs
Annual ryegrass-red clover and winter rye-hairy vetch mixtures were interseeded into established corn in June, in August, and broadcast seeded after corn harvest. Corn received N fertilizer from compost or heap manure. For the winter rye-hairy vetch binary mixture, grass and legume populations averaged 117 and 336 plants/m2, respectively; and for the annual ryegrass-red clover binary mixture grass and legume populations averaged 642 and 238 plants/m2, respectively. Legume and grass populations two weeks following seeding were greater for the June than for the August seeding but survival of seedlings from both planting till fall was poor. Compost or heap manure amendments did not affect cover crop populations. Cover crop or fertility treatments had no effect on corn grain yields. We concluded that soil moisture was an important limiting variable affecting successful interseeding of cover crops into corn. Canada thistle is a noxious perennial weed that is particularly
hard to control in organic production systems that cannot use herbicides. Use of buckwheat, pea, and pearl millet cover crops and continuous tillage resulted in November Canada thistle populations of 2.9, 1.8, 1.4, 0.4 plants m2. Suppression of Canada thistle by cover crops was greatly influenced by the density of cover provided by each species. Identification of a cover crop system that includes a marketable product would enhance profit for producers while providing weed control. In long-term organic production system research, grass and broadleaf weed populations were reduced in a four-year rotation including alfalfa compared to a two-year corn-soybean rotation. Including late summer and fall seeded winter rye or hairy vetch cover crops in rotations did not consistently affect weed populations or corn and soybean yields. Corn and soybean grown in a high purchased input system that utilizes herbicides had lower weed populations than corn or soybean grown in organic systems that
depend on tillage for weed control. For a two-year corn and soybean rotation, high input corn grain yields averaged 7200 kg per ha while organically grown corn grain yields averaged 4200 kg per ha. For a four-year rotation that included alfalfa, corn grain yields averaged 6700 kg per ha while corn grain yields in an organic system averaged 6500 kg per ha. Inclusion of cover crops did not increase corn yields in either the two- or four-year rotation.
Impacts
This research provides information to producers on practices that are suitable in organic production systems. Since N fertilization using livestock and green manures, and weed control were determined to be important factors limiting production, these topics are the subject of research on-farm and on the Elwell Agroecology farm in southwestern Minnesota.
Publications
- No publications reported this period
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Progress 01/01/03 to 12/31/03
Outputs
Annual ryegrass-red clover and winter rye grain-hairy vetch mixtures were interseeded into established corn at the last cultivation and in August and broadcast seeded after corn harvest. Timely rains following each seeding resulted in satisfactory initial populations or grasses and legumes of greater than 200 plants/m2 , but subsequent drought conditions and the resulting dry soils greatly reduced these populations in to the fall to levels less than those achieved through a broadcast seeding after harvest. We concluded that soil moisture was an important limiting variable affecting successful interseeding of covers into annual crops. Canada thistle is a noxious perennial weed that if uncontrolled can have significant negative effects on crop yields. A long-term study was initiated at Lamberton and Madison for control of Canada thistle in organic production systems. Continuous tillage, beginning in June, resulted in greater thistle populations than continuous tillage
beginning in May, or than spring-seeded buckwheat or oat cover crops. Suppression of Canada thistle by cover crops was greatly influenced by the density of cover provided by each species. In long-term organic production system research, the effectiveness of manure and legume green manure crops as suppliers of N was evaluated. Manure application to meet N needs of a corn crop has resulted in excessive levels of soil P thereby necessitating reduction in manure application rates. Hairy vetch that was interseeded into standing soybean was not effective in supplying N because of inadequate stands. Hairy vetch stands were reduced by excessive residue on the soil surface following crop harvest. Although hairy vetch has been used extensively as a cover crop, variability among ecotypes in winter survival and spring regrowth is unknown. There are no available varieties. Research was initiated to evaluate the diversity in yield and persistence of hairy vetch ecotypes that are grown throughout
the region. Three major educational activities transferred information about organic production techniques to over 150 producers. Topics included cover cropping, weed control, and soil organic matter. A listening session was also held for over 30 producers and community members to provide input in the direction of organic research and education. Marketing and consumer education were identified as important areas needing attention. On-farm research was initiated to evaluate the effect of timing of winter rye grain suppression on weed suppression and yield of an interseeded soybean crop.
Impacts
This research provides information to producers on practices that are suitable in organic production systems. Since N fertilization using livestock and green manures, and weed control were determined to be important factors limiting production, these topics are the subject of research on-farm and on the Elwell Agroecology farm in southwestern Minnesota.
Publications
- Evans, E., Porter, P., Dyck, E., Nickel, P., Nickel, L., Sheaffer, C., Wyse, D. Allan, D., and Harbur, M. 2003. An update on organic research and outreach at the University of Minnesota Southwest Research and Outreach Center. Agron. Abst. p. 303.
- Sheaffer, C.C., and Seguin, P. 2003. Forage legumes for sustainable cropping systems. p. 187-216. In A. Shrestha (ed). Cropping systems. Trends and Advances. The Haworth Press, Inc., Binghamton, NY.
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Progress 01/01/02 to 12/31/02
Outputs
To enhance the N and organic matter input into organic cropping systems as well as to provide ground cover, a mixture of annual legumes including hairy vetch and annual medic was successfully seeded into soybean at the last spring cultivation. Winter rye was seeded into corn. Populations of legumes and rye were about 7 and 12 plants/square meter. Factors identified as limiting establishment included surface soil moisture deficits and inadequate light due to crop canopies and crop residues. To provide N for growth of a subsequent corn crop, heap manure was fall applied at rates of 10 Mg/ha for 4-year rotations containing oat-alfalfa-corn-soybean and 20 Mg/ha for a 2-year corn-soybean rotation. Although both systems require N and organic matter from manure, there is concern regarding excessive buildup of P in the soil. About 100 students from across the USA attended a 3 day organic field school in organic farming systems that was held at the Elwell Agroecology Farm.
Topics including composting of manure, cover cropping, soil health, and weed control.
Impacts
Basic information provided on use of legume cover crops and manures in organic production systems will increase the efficiency and profitability of organic farmers and reduce the cost of organic foods. Education is critical in increasing the efficiency of organic production.
Publications
- No publications reported this period
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