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25 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Legume N fixation? |
N fixation, a process in Which N (N2) in the atmosphere is converted into ammonia (NH3). A symbiotic relationship between a host and rhyzobia bacteria typical legumes white clover. Rhyzobia unavailable N in the soil to the plant and the atmosphere. Plants feed the rhyzobia with carbs. |
N fixing - atmosphere Rhizobia |
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Forage legume properties |
High in protein N fixing Improved soil structure - fibrous root system aerates soil |
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Why has there been a decline in legume sales |
Numbers have been declining in the 20th century mainly due to changes in agricultural practices e.g. nitrogen fertiliser. Sales of legumes are recovering from organic movements and increasing N fertiliser prices and the benefit of clover to ruminates. 1987 red clover breeding stop and sales drop from 2,000 t to just 50 t (1980-1990) |
Change in agricultural practices |
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Species of interest |
White clover Red clover Lucerne Birds foot trefoil- grows well in low fertility soils. High in tannin which reduced bloat also high in antihelminthic properties |
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White clover use and properties |
Grazing and often grown with PRG N fixed supplied to combined plant High digestibility and protein Classified by leaf size
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Benefits of white clover |
Increases milk yield by 6%, increases milk solids. High palatability Can proved 150kg/ha of N for grass growth High protein and mineral content Increased animal performance |
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Red clover properties |
Higher yielding than white clover and often used for silage Easily damaged by over grazing Older varieties - 3rd year crop becomes patchy New varieties - persist for 4/5 years |
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Red clover benefits |
Increased milk yield by 4% than PRG silage Lambs have higher growth rates by 4%, higher carcass weight and quicker finishing Red clovers contain phytoestrogens which increase animal growth Increased biodiversity 3 cuts High yields with no or low N fertiliser High protein content (up to 19% in silage) Good for silage and finishing stilock in autumn |
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Nitrogen fixation (legumes) Legume attributes |
N fixing - supply N, no significant added costs Increased soil N content High value, energy, protein, minerals |
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N fixation |
Symbiotic relationship between the plant and rhizobia, rhizobia fix N Rate and quantity of fixed N influenced by: environment (soil and atmosphere) And management |
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Quantities of N fixed |
Largest values: U.K. 455kg/ha/annum Nethalands 565kg/ha/annum NZ 670kg/ha/annum
Typical values: U.K. 65-280kg/ha NZ 185kg/ha (mean value) |
Largest and typical values of fixed N |
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Potential role of forage legumes |
Grow as N self-sufficient crop e.g. Lucern Rely partly/greatly on N transfer to companion crop e.g. Grass/WC or peas or beans/cereals and WC/cereals (has seasonal variations) Rely on provision of residual N to following crop |
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Annual production (t DM/ha) of grass and white clover cut monthly |
Back (Definition) |
Grass with 200kg N = 7t DM/ha Grass clover no N = 7.8t DM/ha Grass clover with 200kg N = 9t DM/ha Grass 400kg N = 10t DM/ha |
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Grass with N vs grass clover |
Grass with 200kg N will give 7t DM/ha where as grass and clover will provide 7.9t DM/ha Cheaper to use PRG/clover compared to PRG and 200kg N fertiliser |
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Potential draw drawbacks of legumes |
N fixation is related to plant needs Distribution of fixed N cannot be regulated |
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Challenges |
Optimising N fixation so you don't produce unnecessary N Enhancing or regulating N transfer Creation of systems |
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Potential draw drawbacks of legumes |
N fixation is related to plant needs Distribution of fixed N cannot be regulated - N fixed in late summer can result in large residue of N in the soil in Autumn when it can't be utilised N needs to be made available in the right place at the right time - Could plant winter wheat in early autumn to soak up N |
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Potential benefits of legumes |
Reduced dependents on fossil energy and industrial N fertiliser Lower harmful emission (green house gasses) and nitrates Lower production costs Higher productivity Increased protein self-sufficiency |
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Contribution to key challenges |
Increase forage yield; improves N fixation and raises efficiency of protein conversion Substituting inorganic fertiliser N with symbiotic N Mitigation + facilitating adaptation to climate change Increase herbage nutritive value + raising efficiency of protein convention. Polyphenoloxidases in red clover protects protein from degradation in the rumen |
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Continuous and Rotational cattle grazing of clover |
Continuous grazing by cattle increased herbage yield (t DM/ha) of clover and animal live weight gain (820kg/ha) compared to 28 day rotational grazing (755kg/ha) |
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Lamb production from grass + 250kg N/ha or grass + WC with no N. Continuous V rotational grazing |
Continuous grazing resulted in lamb weight gain + ewe weight loss Rotational grazed ewes gained weight on PRG/WC PRG/WC increased lamb performance when rotational grazed compared to continuous grazing |
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Down side to continuous grazing WC |
It hammers the clover components from trampling, no rest to re grow
Rotational means there' is more clover as it has time to regenerate |
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Incorporation into systems |
Adoption of appropriate grazing systems (different grazing systems at different times of the year) Monitoring % of legume in pasture and use of management strategies to regenerate plant Strategic use of N fertiliser to encourage early spring grass growth Means of introducing/re-introducing legumes in cases of depression or crashes |
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Legume papers Legume advantages when down in mixed swards at 30-50% (luscher et al 2014 + Erikson, et al 2012) |
Increased forage production Green house gas neutral + energy neutral N input into grassland via symbiotic N2 fixation Higher livestock performance (kleen et al 2011) Enhanced efficiency of protein digestion in ruminants Increased animal health, reduced need for medication High nutrient value + intake of forage with less marked decline of sward quality Support of non N2 fixing plants though transfers of symbiotic fixed N |
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Papers Limitations - most important areas for research are as followed |
Needs more predictable and controllable proportions of legumes within mixed plant communities. This may be achievable through innovative management strategies, optimised seed mixtures + breeding for increased compatible ability Need improved nutritive value of fresh forage + especially silage which can be addressed by optimising he energy/protein balance with in the plants (increase WSC concentration) |
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