Warmer than average autumn temperatures are increasing risk of lodging in oilseed rape crops due to mineral and trace element deficiency, growers have been warned.
With many 2011 crops exhibiting such high levels of vigour, growers are advised to ensure plants receive adequate boron if they are to achieve their potential.
"OSR crops are ahead because of the continuing warm conditions," says Paul Haynes of Barclay Crop Protection. "Crops are denser than expected, putting greater demand on soil reserves and hugely increasing the risk of lodging. So growers should focus on ensuring the strongest root systems possible, which means focusing on the availability of micro-nutrients as well as major ones."
Crops have established at a time when boron availability in the soil is low following extended dry conditions in many areas. "Soils where rape is already in the rotation are most likely to have insufficient boron to meet crop demands," explains Mr Haynes. "Current trends mean that cropping intervals may be closer than ideal with at least 80grams/ha of boron removed at each OSR harvest."
Boron is crucial in rape’s metabolism; the highest demand occurs when the crop is actively growing as it is essential for cell wall structure. Young plants need to rapidly develop their root systems to supply anchorage, moisture and nutrients. During this period, any shortage of nutrients limits yield potential and standing ability.
"Growers who have applied lime ahead of a rape crop need to bear in mind that this can reduce the availability of nutrients such as manganese and boron in the soil. Those choosing modern hybrid rape varieties also need to be aware that higher potential means higher nutritional requirements.
"The estimated boron requirement of OSR crops can range from 200-400g/ha, and possibly higher still in calcareous soils. Given the immediate need for strong roots to prevent lodging later, growers should consider a split application rather than risk leaving boron application to the usual spring timing," advises Mr Haynes. "At the current growth stage, a boron product such as SoluborR should be applied at a rate of 1–1.5kg/ha, followed up with another 1-1.5kg/ha of Solubor in spring. This ensures the plant makes best use of the element.
"Because it’s a foliar application, Solubor can be incorporated into a tank-mix with
propyzamide or an autumn fungicide, minimising workloads and eliminating the need for an extra pass."
Soil testing pre-planting should have revealed any underlying deficiency. "But at this stage leaf tissue analysis will give the most accurate picture and provide target requirements for boron applications," adds Mr Haynes. "Severe deficiencies will have visual symptoms: new leaves may be deformed, petioles cracked and bent back, stem elongation will be restricted and plants will be stunted. In extreme cases growing points may die or plants will demonstrate excessive branching and have hollow or cracked roots and bases."
