Abstract
Defoliation management of forage species in the northern USA is related to total nonstructural carbohydrate (TNC) concentrations. These energy compounds are closely related to winter survival, stand persistence, and subsequent productivity of stands. Influences of early spring defoliation on TNC concentrations of switchgrass ( Panicum virgatum L.) during recovery growth in the humid USA have not been reported. This field study was conducted to observe influences of defoliation time and intensity on TNC concentrations during recovery growth when switchgrass was grown without or with N fertilization (120 kg N ha −1 ). The experimental site was a Webster‐Nicollet soil complex (fine‐loamy, mixed, mesic Typic Haplaquolls‐Aquic Hapludolls). Defoliation treatments at 2‐wk intervals in 1984 and 1985 consisted of early‐, mid‐, and late‐spring defoliation, each at moderate or severe intensity. Nitrogen fertilization reduced TNC concentrations for all defoliation treatments. Accumulated TNC concentrations remained lower after 3, 6, and 9 wk of recovery growth for 120 compared with 0 kg N ha −1 , but relatively little difference was observed among defoliation treatments in TNC concentrations by mid‐October. Severe defoliation at early, mid, and late spring generally contributed to lower TNC concentrations during recovery growth compared with moderate defoliation. However, TNC concentrations 6 to 8 wk or less after spring defoliation were at a relatively high concentration for most defoliation treatments, which suggests that herbage utilization in mid‐ to late‐July should not seriously weaken stands. Lower TNC concentrations in mid‐October of 1985 compared with 1984 suggest that both weather conditions and defoliation management influence TNC concentrations in stem bases of switchgrass.
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Claims 7
Claim · model-written summary
Nitrogen fertilization reduced TNC concentrations across defoliation treatments.
- Taxon
- switchgrass
Panicum virgatumt0 - Treatment
- Nitrogen fertilizatione0
- Outcome
- TNC concentrationse0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogen fertilization reduced TNC concentrations for all defoliation treatments”
t0“Switchgrass”
Claim · model-written summary
TNC remained lower after 3, 6, and 9 weeks with 120 versus 0 kg N ha−1.
- Taxon
- switchgrassPanicum virgatumt0
- Organ / stage
- recovery growthe0
- Treatment
- 120e0
- Outcome
- TNC concentrationse0
- Direction
- lowere0
- Comparator
- 0 kg N ha −1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Accumulated TNC concentrations remained lower after 3, 6, and 9 wk of recovery growth for 120 compared with 0 kg N ha −1”
t0“Switchgrass”
Claim · model-written summary
By mid-October, TNC concentrations differed little among defoliation treatments.
- Taxon
- switchgrassPanicum virgatumt0
- Treatment
- defoliation treatmentse0
- Outcome
- TNC concentrationse0
- Direction
- little differencee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“relatively little difference was observed among defoliation treatments in TNC concentrations by mid‐October”
t0“Switchgrass”
Claim · model-written summary
Severe spring defoliation generally lowered TNC during recovery compared with moderate defoliation.
- Taxon
- switchgrassPanicum virgatumt0
- Treatment
- Severe defoliatione0
- Outcome
- TNC concentrationse0
- Direction
- lowere0
- Comparator
- moderate defoliatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Severe defoliation at early, mid, and late spring generally contributed to lower TNC concentrations during recovery growth compared with moderate defoliation”
t0“Switchgrass”
Claim · model-written summary
TNC was relatively high up to 6 to 8 weeks after spring defoliation for most treatments.
- Taxon
- switchgrassPanicum virgatumt0
- Outcome
- TNC concentrationse0
- Direction
- highe0
- Qualifier
- 6 to 8 wk or lesse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“TNC concentrations 6 to 8 wk or less after spring defoliation were at a relatively high concentration for most defoliation treatments”
t0“Switchgrass”
Claim · model-written summary
Mid-July herbage use should not seriously weaken switchgrass stands.
- Taxon
- switchgrassPanicum virgatumt0
- Outcome
- herbage utilization in mid‐ to late‐Julye0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“herbage utilization in mid‐ to late‐July should not seriously weaken stands”
t0“Switchgrass”
Claim · model-written summary
TNC concentrations were lower in mid-October 1985 than in 1984.
- Taxon
- switchgrassPanicum virgatumt0
- Outcome
- TNC concentrationse0
- Direction
- Lowere0
- Comparator
- 1984e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Lower TNC concentrations in mid‐October of 1985 compared with 1984”
t0“Switchgrass”
The same questions in other papers
fertilization · quality: sugar starch · Panicum virgatum (switchgrass)Positive and negative results
2 in the opposite direction
- positive
- 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.