Boron on Oilseed Rape
All
crops require B though the requirement is less in monocots than in dicots.Brassicae species have a high requirement
for B
Removal
of crops and leaching of B is leading to a decrease in soil B levels
B
Deficiency
B deficiency commonly occurs on coarse textured
soils
Decreasing organic matter levels in soils
increase risk of B deficiency
Heavy rainfall can exacerbate B deficiency
Hot dry weather can increase B deficiency as
lower soil levels usually have lower B levels
Climatic factors, which reduce transpiration, may
reduce the amount of B moving to flowers
High light intensities increase sensitivity to B
deficiency
B in plants
B is implicated in:
Sugar transport
Cell wall synthesis
Lignification
Carbohydrate metabolism
Respiration
Auxin metabolism
Effects of B deficiency
Boron deficiency inhibits root growth
Uptake of P is lower in the root tips of B
deficient plants
B deficiency can result in cracked stems
In some plants insect damage has been shown to be
higher in B deficient plants
B is required for pollen tube growth and pollen
viability and thereby for seed development
B deficient crops are more susceptible to frost
damage
B requirement
A 4 t/ha crop of OSR requires 320g Boron for
growth and removes 80g/ha B in the crop ( Sharrocks)
Application
Application of B to the
soil can provide season long elevation of the B status of the crop
Rate 1-2 kg/ha B
Movement of B in annual
crops is limited, thus applications to the foliage will have little effect on
the pollination and seed set - several applications have been shown to be more
effective than a single application
Some of the B applied
to foliage will reach the ground and be absorbed by roots
Sharrocks recommends
application of 1-2kg/ha B regardless of method of application- this is in line
with the view that the efficacy of foliar applications during the early growth
of annual crops depends on absorption by roots as well as leaves, and the poor
phloem mobility of B