Abstract
Intercropping legumes may reduce inputs and enhance sustainability of forage and feedstock production, especially on marginal soils. This approach is largely untested for switchgrass (Panicum virgatum L.) production, yet producer acceptance should be high given the traditional use of legumes in forage/agricultural systems. Our objectives were to evaluate three cool-season and two warm-season legumes and their required densities to influence yield and supply nitrogen (N) compared to three inorganic N levels (0, 33, and 66 kg N ha−1 [0, 30, and 60 lb N ac−1]) at three locations in Tennessee (Knoxville [Sequatchie Silt Loam], Crossville [Lilly Loam], and Milan [Loring B2 Series]). Fall of 2010 seeded, cool-season legumes (red clover [Trifolium pratense L.], hairy vetch [Vicia villosa L.], ladino clover [Trifolium repens L.]), arrowleaf clover (Trifolium vesiculosum L.), and a spring of 2011 seeded, warm-season legume (partridge pea [Chamaecrista fasciculate L.]) were interseeded into switchgrass at three (high, medium, and low) seeding rates each in two experiments. Harvest treatments were annual single, postdormancy biofuel (Experiment One) or integrated forage-biofuel (preanthesis and postdormancy; Experiment Two). Year one yield impacts were minimal. During the second harvest year, legumes increased yield versus Year 1; in general, yields for 33 and 67 kg N ha−1 did not differ from those for red clover, hairy vetch, ladino clover, or partridge pea (p < 0.05). Arrowleaf clover yields were not different from 0 kg N ha−1. Forage biomass yields were generally more responsive to legumes (p < 0.05) than the biomass regime. Legume persistence after three years was generally greatest for ladino clover and partridge pea. Forage quality (switchgrass only) in some cases was positively influenced by legume treatments, notably hairy vetch and partridge pea (p < 0.05). Intercropping selected legumes in switchgrass may enhance forage quality and yield while reducing nonrenewable inputs, fertilizer costs, and emissions/runoff to air and groundwater.
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Claims 13
Claim · model-written summary
Yield impacts in year one were minimal.
- Taxon
- Switchgrass
Panicum virgatumt0 - Outcome
- yield impactse0
- Direction
- minimale0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Year one yield impacts were minimal.”
t0“Switchgrass”
Claim · model-written summary
In the second harvest year, legumes increased yield relative to year one.
- Taxon
- SwitchgrassPanicum virgatumt0
- Treatment
- legumese0
- Outcome
- yielde0
- Direction
- increasede0
- Comparator
- Year 1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“During the second harvest year, legumes increased yield versus Year 1”
t0“Switchgrass”
Claim · model-written summary
Second year yield under red clover did not differ from 33 and 67 kg N ha−1 fertilization.
- Taxon
- SwitchgrassPanicum virgatumt0
- Treatment
- red clovere0
- Outcome
- yieldse0
- Direction
- did not differe0
- Comparator
- 33 and 67 kg N ha−1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“yields for 33 and 67 kg N ha−1 did not differ from those for red clover, hairy vetch, ladino clover, or partridge pea (p < 0.05)”
t0“Switchgrass”
Claim · model-written summary
Second year yield under hairy vetch did not differ from 33 and 67 kg N ha−1 fertilization.
- Taxon
- SwitchgrassPanicum virgatumt0
- Treatment
- hairy vetche0
- Outcome
- yieldse0
- Direction
- did not differe0
- Comparator
- 33 and 67 kg N ha−1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“yields for 33 and 67 kg N ha−1 did not differ from those for red clover, hairy vetch, ladino clover, or partridge pea (p < 0.05)”
t0“Switchgrass”
Claim · model-written summary
Second year yield under ladino clover did not differ from 33 and 67 kg N ha−1 fertilization.
- Taxon
- SwitchgrassPanicum virgatumt0
- Treatment
- ladino clovere0
- Outcome
- yieldse0
- Direction
- did not differe0
- Comparator
- 33 and 67 kg N ha−1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“yields for 33 and 67 kg N ha−1 did not differ from those for red clover, hairy vetch, ladino clover, or partridge pea (p < 0.05)”
t0“Switchgrass”
Claim · model-written summary
Second year yield under partridge pea did not differ from 33 and 67 kg N ha−1 fertilization.
- Taxon
- SwitchgrassPanicum virgatumt0
- Treatment
- partridge peae0
- Outcome
- yieldse0
- Direction
- did not differe0
- Comparator
- 33 and 67 kg N ha−1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“yields for 33 and 67 kg N ha−1 did not differ from those for red clover, hairy vetch, ladino clover, or partridge pea (p < 0.05)”
t0“Switchgrass”
Claim · model-written summary
Arrowleaf clover yield did not differ from zero nitrogen fertilizer.
- Taxon
- SwitchgrassPanicum virgatumt0
- Treatment
- Arrowleaf clovere0
- Outcome
- yieldse0
- Direction
- not differente0
- Comparator
- 0 kg N ha−1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Arrowleaf clover yields were not different from 0 kg N ha−1.”
t0“Switchgrass”
Claim · model-written summary
Forage biomass yield responded more to legumes than to the biomass harvest regime.
- Taxon
- SwitchgrassPanicum virgatumt0
- Treatment
- legumese0
- Outcome
- Forage biomass yieldse0
- Direction
- more responsivee0
- Comparator
- biomass regimee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Forage biomass yields were generally more responsive to legumes (p < 0.05) than the biomass regime.”
t0“Switchgrass”
Claim · model-written summary
Ladino clover persisted relatively well after three years.
- Taxon
- SwitchgrassPanicum virgatumt0
- Material
- ladino clovere0
- Outcome
- Legume persistencee0
- Direction
- greateste0
- Qualifier
- after three yearse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Legume persistence after three years was generally greatest for ladino clover and partridge pea.”
t0“Switchgrass”
Claim · model-written summary
Partridge pea persisted relatively well after three years.
- Taxon
- SwitchgrassPanicum virgatumt0
- Material
- partridge peae0
- Outcome
- Legume persistencee0
- Direction
- greateste0
- Qualifier
- after three yearse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Legume persistence after three years was generally greatest for ladino clover and partridge pea.”
t0“Switchgrass”
Claim · model-written summary
Hairy vetch improved switchgrass forage quality in some cases.
- Taxon
- switchgrassPanicum virgatume0
- Treatment
- hairy vetche0
- Outcome
- Forage qualitye0
- Direction
- positively influencede0
- Qualifier
- in some casese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Forage quality (switchgrass only) in some cases was positively influenced by legume treatments, notably hairy vetch and partridge pea (p < 0.05).”
Claim · model-written summary
Partridge pea improved switchgrass forage quality in some cases.
- Taxon
- switchgrassPanicum virgatume0
- Treatment
- partridge peae0
- Outcome
- Forage qualitye0
- Direction
- positively influencede0
- Qualifier
- in some casese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Forage quality (switchgrass only) in some cases was positively influenced by legume treatments, notably hairy vetch and partridge pea (p < 0.05).”
Claim · model-written summary
The authors suggest selected legume intercrops could enhance switchgrass forage quality and yield and reduce inputs and emissions.
- Taxon
- switchgrassPanicum virgatume0
- Outcome
- Intercropping selected legumes in switchgrass may enhance forage quality and yield while reducing nonrenewable inputs, fertilizer costs, and emissions/runoff to air and groundwater.e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Intercropping selected legumes in switchgrass may enhance forage quality and yield while reducing nonrenewable inputs, fertilizer costs, and emissions/runoff to air and groundwater.”
The same questions in other papers
Trifolium pratense · yield · Panicum virgatum (switchgrass)Positive and negative results
1 paper in the same direction as this paper · 1 reporting no difference from an alternative
- positive
- no effect
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.