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8/3/2019 Efficient Fertility Building with Tailored Legume Mixtures
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Efficient fertility building with tailored legume mixtures —
improving N use efficiency
The Legume LINK project is funded byDefra and industry partners.
Legume LINK aims to improve fertility building us-ing green manures. It will develop the means to
create tailored legume mixtures optimised tofix the required quantity of N;transfer N to the subsequent cropwith the appropriate timing;perform reliably under local environ-mental conditions.
12 legume species with arange of growth habits and
physical compositions arebeing trialled at 6 researchsites, together with 4 grassspecies. A mixture com-prising the 4 grasses and 10of the legumes is beinggrown on 35 farms acrossthe UK (see map). The per-formance of the individual
species and of the mixtureare being monitored.
Soil Nitrogen 70% of nitrate found in the UK’s waterways originates from leaching off agricultural land. In addi-
tion to the environmental implications of this, nitrate leaching from the farm also represents an economic loss to
the farmer as the N that has been purchased is not being converted into crop productivity.
Reducing the use of mineral N
Low-input and organic systems often use fertility building crops, typically legumes, as an alternative to mineral N.
A clover ley can accumulate up to 200 kg N/ha/yr allowing the farmer to significantly reduce or even eliminate
external inputs of mineral N. However, leys do not always deliver reliably, and there is a need to improve their
fertility-building capability and resilience. Problem 1 — Developing a ley that can reliably build sufficient
fertility for the subsequent crop
Synchrony of N demand and supply
After ploughing in, the legumes decompose and release N into the soil. However, there is often a lack of synchrony between the release of N
from the legumes and its uptake by the subsequent crop. This can lead to significant leaching of N from the system, representing a loss of valu-
able nutrients and causing environmental damage. Problem 2 —
Controlling the quantity and timing of N release
Reliable performance
A successful fertility building crop must be capable of establishing well, suppressing weeds and performing under the range of growing condi-
tions it is likely to encounter in low-input and organic production systems. A typical ley of one or two species is vulnerable to failure under
unfavourable growing conditions. Problem 3 — Developing a ley that is resilient in the absence of agrochemicals
The problem
8/3/2019 Efficient Fertility Building with Tailored Legume Mixtures
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The solution
Reducing mineral N: The legume mix optimises fertility building without mineral nitrogen.
Synchrony — supply and demand: A legume mix can be tailored to supply N to the subsequent crop when
it needs it and reduce leaching.
Reliable performance: Each plant species performs within a limited range of growing conditions. A single-
species crop can fail under unfavourable growing conditions; a mixture is more resilient and hedges risk.
Biodiversity: An additional benefit of a diverse legume mix is a greater range of flowers, which should attract
a greater number of insect species including important pollinators. This aspect of the mix and its effects for
agro-ecosystem health are being examined as part of a PhD project in collaboration with Legume LINK.
The benefits
In the Legume LINK project we are investigating an approach that aims to
solve the three problems identified overleaf: growing a diverse legume-based
mixture.
Mixtures and diversity
Different legume species have different growth characteristics and nutrient use profiles.
This means by growing a complex mixture of legume species we can maximize the exploitation
of available nutrients. Also, we can use the inherent variation in the residue composition to
control the N dynamics of the ley, manipulating the amount of N accumulated as well as the rate and timing of its release into the soil. For ex-
ample, properties such as lignin content affect the rate at which species decompose and release N into the soil. Some species break down and
release nutrients comparatively quickly while others do so gradually over a longer period of time.
In the Legume LINK project we are trialling a mixture of 14 species. Assessments are being carried out on the establishment success of each
of the species, on their growth rate and heights, biomass production, weed suppression, N accumulation and their residue breakdown proper-
ties. We will use these data to generate legume based mixtures that will be suited to different regions of the UK and that can reliably build soil
fertility and transfer it efficiently to the next crop.
The Legume LINK project is led by the Organic Research Centre, Elm Farm, being oneof its many crop research projects. For more information contact:
Dr Thomas Döring, The Organic Research Centre - Elm Farm, Hamstead Marshall. RG20 0HR,
Tel. office: 01488 658 298 – option 1, 5
