Abstract
Interseeded clover. Photo courtesy of Heather Karsten. Farmers use “green manure” to protect soil, fix nitrogen, and scavenge nutrients when cash crops are not present. These cover crops can also reduce weeds and act as a mulch for cash crops in no-till systems. Because of the increasing use of cover crops in no-till systems, researchers at Penn State recently compared two green manure cover crops, red clover (Trifolium pratense L.) and hairy vetch (Vicia villosa Roth). “One of the reasons that we compared these was that farmers have started interseeding red clover,” says ASA member Heather Karsten, Associate Professor of Crop Production/Ecology. Interseeding, she explains, is also called relay cropping where farmers frost seed or drill red clover into a small grain very early in the spring. Karsten is a co-author on a study recently published in Agronomy Journal, titled “Green Manure Comparison between Winter Wheat and Corn: Weeds, Yields, and Economics.” The authors report that red clover treatments were more profitable than hairy vetch due to increased cash crop yield and reduced herbicide application. Dr. William Curran, Weed Extension Specialist and ASA member, had done prior research using hairy vetch in organic farming systems. As a co-author on this paper, Curran says, “I went into this thinking hairy vetch would be the winner … the results of this study surprised me a little bit.” The experiment was conducted at the Russell E. Larson Agricultural Research Station in Pennsylvania. From 2010 to 2013, green manures were used in a winter cereal–green manure–corn silage rotation. As Karsten mentioned, the red clover treatment was interseeded into the cereal grain crop whereas the hairy vetch, which was combined with triticale, was planted after the wheat harvest. Red clover was harvested for hay in late fall before corn was planted the following spring, and both cover crop treatments were terminated with herbicide in spring prior to corn planting. Corn yields were consistently greater in red clover treatments. The difference was significant in 2012 and 2013 when corn yields were 16 and 9% greater, respectively, in red clover treatments compared with hairy vetch. “We don't have all the explanations for why,” admits Karsten, but she says in 2012 and 2013, corn populations were significantly higher after red clover, and corn pest populations appear to be the culprits although there may also have been more nitrogen available from clover. View the open access Agronomy Journal article, “Green Manure Comparison between Winter Wheat and Corn: Weeds, Yields, and Economics,” online at https://doi.org/10.2134/agronj2016.02.0084 There was little difference in weed control, measured as weed biomass, between the two green manure treatments. However, red clover required fewer herbicide applications in the spring, amounting to a 28% reduction in herbicide active ingredient use. “Anytime you can use less herbicide, it's an advantage,” says Curran, both economically by reducing costs, and ecologically by reducing selection for herbicide-resistant weed biotypes. The economic benefits of increased yield, reduced herbicide, and harvesting red clover as forage were calculated as $1,355/ha more in net returns compared with hairy vetch. Even without the harvest of red clover for forage, the red clover treatments would have $123/ha greater profit than hairy vetch. The results of this study may lead more farmers, agronomic consultants, and educators to consider the use of red clover as a green manure. “I know of conventional and organic dairy and grain farmers in Pennsylvania and New York who relay crop red clover into wheat before corn,” Karsten says. “And now, we have multiple reasons to recommend red clover over hairy vetch to more growers.” Although red clover was the higher-performing green manure in this system, the authors point out that there are some limitations. Karsten explains that if wheat fields have high weed pressure, “then this interseeding might not be the best practice, but if weed populations are manageable and the typical sequence does involve rotating to corn, then we think this is a good strategy.” Cover crops are not a cure-all and need to be used strategically. Before starting to use green manure, Curran advises farmers to “really think through the process,” meaning that farmers should take into account what benefits they hope to gain from using a green manure and how they will manage both the green manure and cash crops throughout the growing season.
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Claims 10
Claim · model-written summary
Red clover green manure treatments were more profitable than hairy vetch.
- Taxon
- red clover
Trifolium pratensee0 - Treatment
- red clover treatmentse0
- Outcome
- profitablee0
- Direction
- more profitablee0
- Comparator
- hairy vetche0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The authors report that red clover treatments were more profitable than hairy vetch due to increased cash crop yield and reduced herbicide application”
Claim · model-written summary
Corn yields were consistently greater in red clover treatments than in hairy vetch treatments.
- Taxon
- Corn
Zea mays subsp. mayse1 - Treatment
- red clover treatmentse1
- Outcome
- Corn yieldse1
- Direction
- greatere1
- Comparator
- hairy vetche0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“compared two green manure cover crops, red clover (Trifolium pratense L.) and hairy vetch (Vicia villosa Roth)”
e1“Corn yields were consistently greater in red clover treatments”
Claim · model-written summary
Corn yield was 16% greater in red clover treatments than in hairy vetch in 2012, a significant difference.
- Taxon
- cornZea mays subsp. mayse0
- Treatment
- red clover treatmentse0
- Outcome
- corn yieldse0
- Direction
- greatere0
- Value
- 16e0
- Qualifier
- 2012e0
- Comparator
- hairy vetche0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The difference was significant in 2012 and 2013 when corn yields were 16 and 9% greater, respectively, in red clover treatments compared with hairy vetch”
Claim · model-written summary
Corn yield was 9% greater in red clover treatments than in hairy vetch in 2013, a significant difference.
- Taxon
- cornZea mays subsp. mayse0
- Treatment
- red clover treatmentse0
- Outcome
- corn yieldse0
- Direction
- greatere0
- Value
- 9%e0
- Qualifier
- 2013e0
- Comparator
- hairy vetche0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The difference was significant in 2012 and 2013 when corn yields were 16 and 9% greater, respectively, in red clover treatments compared with hairy vetch”
Claim · model-written summary
Corn populations were significantly higher after red clover than after hairy vetch in 2012 and 2013.
- Taxon
- cornZea mays subsp. mayse1
- Treatment
- red clovere1
- Outcome
- corn populationse1
- Direction
- highere1
- Qualifier
- 2012 and 2013e1
- Comparator
- hairy vetche0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“compared two green manure cover crops, red clover (Trifolium pratense L.) and hairy vetch (Vicia villosa Roth)”
e1“she says in 2012 and 2013, corn populations were significantly higher after red clover”
Claim · model-written summary
There was little difference in weed biomass between the red clover and hairy vetch green manure treatments.
- Taxon
- red cloverTrifolium pratensee0
- Treatment
- green manure treatmentse1
- Interactor
- weede1weed
- Outcome
- weed biomasse1
- Direction
- little differencee1
- Comparator
- hairy vetche0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“compared two green manure cover crops, red clover (Trifolium pratense L.) and hairy vetch (Vicia villosa Roth)”
e1“There was little difference in weed control, measured as weed biomass, between the two green manure treatments”
Claim · model-written summary
Red clover required 28% less herbicide active ingredient than hairy vetch in spring, with fewer herbicide applications.
- Taxon
- red cloverTrifolium pratensee1
- Treatment
- red clovere1
- Outcome
- herbicide applicationse1
- Direction
- fewere1
- Value
- 28%e1
- Comparator
- hairy vetche0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“compared two green manure cover crops, red clover (Trifolium pratense L.) and hairy vetch (Vicia villosa Roth)”
e1“red clover required fewer herbicide applications in the spring, amounting to a 28% reduction in herbicide active ingredient use”
Claim · model-written summary
Harvesting red clover as forage gave $1,355/ha more in net returns than hairy vetch.
- Taxon
- red cloverTrifolium pratensee0
- Treatment
- harvesting red clover as foragee0
- Outcome
- net returnse0
- Direction
- moree0
- Value
- $1,355/hae0
- Comparator
- hairy vetche0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The economic benefits of increased yield, reduced herbicide, and harvesting red clover as forage were calculated as $1,355/ha more in net returns compared with hairy vetch”
Claim · model-written summary
Without forage harvest, red clover treatments would have $123/ha greater profit than hairy vetch.
- Taxon
- red cloverTrifolium pratensee0
- Treatment
- red clover treatmentse0
- Outcome
- profite0
- Direction
- greatere0
- Value
- $123/hae0
- Qualifier
- Even without the harvest of red clover for foragee0
- Comparator
- hairy vetche0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Even without the harvest of red clover for forage, the red clover treatments would have $123/ha greater profit than hairy vetch”
Claim · model-written summary
The authors recommend red clover over hairy vetch as a green manure for more growers.
- Taxon
- red cloverTrifolium pratensee0
- Outcome
- recommend red clover over hairy vetche0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we have multiple reasons to recommend red clover over hairy vetch to more growers”
The same questions in other papers
Trifolium pratense · yield · Zea mays (maize)Positive and negative results
10 papers in the same direction as this paper · 3 in the opposite direction
- negative
- negative
- negative
10 papers more in this group
See all 14 papers →fertilization · weed · Trifolium pratense (red clover)Positive and negative results
1 reporting no difference from an alternative
- positive
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.