Growing oil seed rape for maximum yield

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Growing oil seed rape for maximum yield
TEMA: RAPS
25 Oil seed rape - the UK way
Growing oil seed rape for maximum yield
Oilseed rape has been shown to have a yield potential of over 6 t/ha (Berry and Spink, 2006)
which is substantially more than achieved on farm in Europe. This paper summarises results from
a long term programme of work in the UK to understand the physiological mechanism of yield
formation for oilseed rape and how crops should be managed to maximise yield.
Dr Pete Berry
ADAS High Mowthorpe
Duggleby, Malton, North Yorkshire YO178BP, UK
[email protected]
Physiological mechanism
of yield formation
The most important component
of yield in oilseed rape is the
number of seeds/m2. Previous
research has shown that crops
with yields of 5t/ha or more almost always required at least
100,000 seeds/m2 to be set.
Seed size was of little importance (Figure 1). Seed number
is determined by the amount
of photosynthesis carried out
by the crop during a 2-3 week
period from late flowering.
Seed numbers are maximised
by achieving an optimum pod
number of 6000 to 8000 pods/
m2 (Figure 2). To achieve this
optimum pod number a green
area index (GAI) of between 3
and 4 units must be achieved
by flowering. Crops with canopies of larger than four tend to
produce more pods, but fewer
seeds/m2 due to low seed set
per pod. Achieving an optimum
sized canopy helps to minimise
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wastage of light due to interception and reflection by flowers
and reduces the risk of lodging.
plant populations were shown to
result in substantial yield reductions in some situations.
Figure 1. Relationship between seed number, seed size and yield
Figure 2. Relationship between pod number, seeds per pod and seed number
Plant population
A series of seed rate experiments carried out in the UK has
shown that the optimum plant
population ranged from 10 to
39 plants/m2 in six experiments
and from 73 to 155 plants/m2
in two experiments with very
severe spring drought (Roques
and Berry, 2015). Super-optimal
Nitrogen management
The crop must take up 50 kg N/
ha to build each unit of GAI.
Therefore to achieve an optimum GAI of 3.5 units by flowering the crop must take up 175
kg N/ha. In order to calculate
how much spring N fertiliser
is required it is vital to take account of the amount N that the
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Oil seed rape - the UK way
crop has taken up during the autumn and winter and the amount
of plant available N that is still
in the soil. In the UK, crops regularly take up more than 100 kg
N/ha during the autumn and winter which substantially reduces
the amount of fertiliser N that is
required. It has been shown that
the majority of N that has been
taken up by the crop by the end
of winter stays in the crop and
contributes toward the target uptake of 175 kg N/ha. Soil mineral N measured to a depth of 60
cm is taken up with an apparent
efficiency of 100%, N fertiliser
applied to the soil is taken up
with 60 % efficiency (although
this can vary). Table 1 gives examples of calculating how much
N fertiliser to apply to crops
with different sized canopies
following winter. Achieving a
crop with a GAI of 3.5 units by
flowering is usually sufficient
to achieve a yield of about 3.5
t/ha. Crops with a higher yield
potential require more N which
should be applied between yellow bud and early flowering to
avoid producing a super-optimal
canopy. For each additional 0.5
t/ha of yield potential above 3.5
t/ha an additional 30 kg of fertiliser N/ha is required.
Plant Growth Regulators
Plant growth regulators are an
important tool for managing the
size of the oilseed rape canopy
and for improving deep rooting.
It has been shown that PGRs
metconazole and tebuconazole
increase yield when applied
to crops with a GAI of greater
than approximately one at the
start of stem extension (Berry
and Spink, 2009). Metconazole
has also been shown to increase
the root length density when applied during early stem extension (Berry and Spink, 2009).
This is important because a recent survey of roots to 100 cm
depth has shown that the majority of oilseed rape crops appear
to have insufficient rooting below a soil depth of about 40 cm
(White et al., 2015).
Conclusions
Optimising the canopy size
of oilseed rape by careful use
of seed rate, N fertiliser rate
and timing and PGRs has been
shown to be very important for
maximising yield potential and
is commonly used in the UK.
In 2015, a UK farmer achieved
a field yield of 6.7 t/ha, which
has been classified as a world
record yield, and helps to illustrate that the high yield potential
of oilseed rape can be achieved
on farms.
References
Berry, P.M. and Spink, J.H.
(2006). A physiological analysis
of oilseed rape yields: Past and
future. Journal of Agricultural
Science, Cambridge 144, 381392.
Berry, P.M. and Spink, J.H.
(2009). Understanding the effect of a triazole with anti-gibberellin activity on the growth
and yield of oilseed rape (Brassica napus). Journal of Agricultural Science, Cambridge 147,
273-285.
Roques, S. and Berry, P.M.
(2015). The yield response of oilseed rape to plant population density. Journal of Agricultural Science, Cambridge. doi:10.1017/
S0021859614001373
White, C., Sylvester-Bradley, R. and Berry, P.M. (2015).
Root length densities of UK
wheat and oilseed rape crops
with implications for water capture and yield. Journal of Experimental Botany. doi: 10.1093/
jxb/erv077.
Table. 1. Examples of how much N fertiliser to apply to crops with different sized canopies.
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