Growersof oilseed rape or brassicas should consider a timely application of boron – itwill pay dividends, says independent crop adviser Peter Parr.
With hightemperatures and abundant moisture, both crops have grown rapidly this autumn.Without sufficient boron, stems are at risk of cracking and growing pointsdying.
If youstart to see those kinds of physical symptoms, unfortunately its too late,warns Mr Parr. Yield will have alreadybeen lost and there is a significant risk of lodging and abnormal growth.
The riskis higher on light sandy soils and those with a high pH, where alkalinityreduces the availability of boron, he says. In addition, rapidly growing crops will have taken up much of theavailable boron and recent heavy rainfall is likely to have caused leaching.
Few soilanalyses reveal adequate levels of boron, says Mr Parr. Occasionally the heaviest soils showsufficient levels but in my experience crops still respond to foliarapplications.
Demandfor boron is at its peak when crops are laying down new tissue. Boron isessential for cell wall structure, continues Mr Parr. Thats why plants witha deficiency display those cracked stems. What you cant always see is the poorroot structures, too.
Sub-optimalroot structures not only make the plant more prone to lodging, but will have afurther knock-on nutritional effect by limiting uptake of other nutrients.
Oilseedrape demands between 200-400g/ha, 80g/ha of which will be removed from thefield during harvest. For some brassicas you can double that – cauliflowersand swedes in particular are very hungry for boron, adds Mr Parr.
Rapidgrowth and high demand for nutrients will continue until temperatures areconsistently low – around 2-3 degrees Celsius, which will be a while yet, hesays. So an application now willprovide crops with what they need until they shut down for winter and willallow them to getting going as soon as conditions allow in spring.
PaulHaynes, of Barclay Crop Protection, suggests the following guide when splittingboron applications.
Aproduct such as Solubor should be applied at a rate of 11.5kg/ha, followed upwith another 1- 1.5kg/ha in spring, he says. There is no need for an extrapass; because its a foliar application, Solubor can be incorporated into atank-mix with propyzamide or an autumn fungicide.