Abstract
Annual and perennial clover species may differ in green manure value. Seven clover (Trifolium) species were grown as annual crops on low fertility (Breton) and high fertility (Edmonton) soils in Alberta. Four annual clovers [balansa (T. michelianum Savi), berseem (T. alexandrinum L.), crimson (T. incarnatum L.), and Persian (T. resupinatum L.)], three perennial clovers [alsike (T. hybridum L.), red (T. pratense L.), and white Dutch (T. repens L.)] and a non-legume reference crop [fall rye (Secale cereale L.)] were ploughed-down as green manure in autumn, and followed by barley (Hordeum vulgare L.). Annual clovers had greater biomass yields than perennial clovers, and berseem clover had the highest yield. At Breton, mean biomass N content was greater for perennial clovers (2.9 g N kg -1 ) than annual clovers (1.9 g N kg -1 ). Clover biomass at Breton yielded an average of 77 kg N ha -1 , with N derived from the atmosphere averaging 88% by N difference method and 75% by 15 N natural abundance method. At Edmonton, the green manures had few effects on soil nitrate and subsequent barley yields. At Breton, all clover green manures except balansa increased barley yields, and grain yields were greater following perennial clovers than annual clovers in one year. Annual clovers will provide forage biomass and add N in areas where rainfall is adequate, and they may be preferable under zero tillage. However there is no advantage of annual clovers, relative to perennial clovers, in terms of N supply.Key words: Green manure, clover, Trifolium species, nitrogen fixation
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Claims 12
Claim · model-written summary
Annual clovers yielded more biomass than perennial clovers.
TrifoliumOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Annual clovers had greater biomass yields than perennial clovers”
Claim · model-written summary
Berseem clover had the highest biomass yield.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“berseem clover had the highest yield”
Claim · model-written summary
At Breton, perennial clovers had higher mean biomass nitrogen content than annual clovers.
- Material
- perennial cloverse0
- Outcome
- mean biomass N contente0
- Direction
- greatere0
- Value
- 2.9 g N kg -1e0
- Qualifier
- 1.9 g N kg -1e0
- Comparator
- annual cloverse0
- Setting
- Bretone0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At Breton, mean biomass N content was greater for perennial clovers (2.9 g N kg -1 ) than annual clovers (1.9 g N kg -1 )”
Claim · model-written summary
Breton clover biomass supplied an average of 77 kg N per hectare.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Clover biomass at Breton yielded an average of 77 kg N ha -1”
Claim · model-written summary
The nitrogen difference method estimated atmospheric nitrogen contribution at 88%.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N derived from the atmosphere averaging 88% by N difference method and 75% by 15 N natural abundance method”
t0“clover species”
Claim · model-written summary
The natural abundance method estimated atmospheric nitrogen contribution at 75%.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N derived from the atmosphere averaging 88% by N difference method and 75% by 15 N natural abundance method”
t0“clover species”
Claim · model-written summary
At Edmonton, green manures had few effects on soil nitrate and subsequent barley yields.
- Taxon
- barley
.jpg?width=60)
Hordeum vulgaree0 - Treatment
- green manurese0
- Outcome
- subsequent barley yieldse0
- Setting
- Edmontone0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“At Edmonton, the green manures had few effects on soil nitrate and subsequent barley yields”
Claim · model-written summary
At Breton, all clover green manures except balansa increased barley yields.
- Taxon
- barleyHordeum vulgaree0
- Treatment
- clover green manures except balansae0
- Outcome
- barley yieldse0
- Direction
- increasede0
- Setting
- Bretone0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At Breton, all clover green manures except balansa increased barley yields”
Claim · model-written summary
In one year, perennial clover green manure preceded greater barley grain yield than annual clover green manure.
- Taxon
- barleyHordeum vulgaree1
- Treatment
- perennial cloverse0
- Outcome
- grain yieldse0
- Direction
- greatere0
- Qualifier
- in one yeare0
- Comparator
- annual cloverse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“grain yields were greater following perennial clovers than annual clovers in one year”
e1“barley (Hordeum vulgare L.)”
Claim · model-written summary
Annual clovers may provide forage biomass and nitrogen where rainfall is adequate.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Annual clovers will provide forage biomass and add N in areas where rainfall is adequate”
Claim · model-written summary
Annual clovers may be preferable under zero tillage.
- Outcome
- preferable under zero tillagee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“they may be preferable under zero tillage”
t0“clover species”
Claim · model-written summary
Annual clovers have no nitrogen supply advantage over perennial clovers.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there is no advantage of annual clovers, relative to perennial clovers, in terms of N supply”
The same questions in other papers
fertilization · yield · Hordeum vulgare (barley)Positive and negative results
472 papers in the same direction as this paper · 66 in the opposite direction · 11 reporting no difference from an alternative
- no effect
- negative
- negative
546 papers more in this group
See all 550 papers →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.