Winter oilseed rape growers delaying planting until late August and into September – due to the dry July thwarting earlier drilling, and to avoid peak cabbage stem flea beetle migration –need to adjust agronomy to compensate for the shortened growing window before winter.

That is the message from Andrew Cromie, ProCam head of crop nutrition, who says winter oilseed rape (WOSR) was largely a success story of the 2026 harvest, with reports of good yields and strong margins relative to other crops, and there is an appetite to grow more.

But it will be vital to build the crop to a suitable size before winter dormancy arrives, he stresses, if growers are to lay the foundations for another good harvest in 2027.

“Farmers are returning to growing WOSR and, weather permitting, we could see plantings increase by 10-20% compared with the 2025-26 season,” Andrew suggests.

“If drilling later, a key objective will be to accelerate the crop’s growth so that it reaches 8-10 true leaves and has a tap root collar diameter of more than 8mm before winter dormancy. This gives it the best chance of having sufficient reserves to grow away again well in spring.

“As a starter, choose a variety with excellent autumn vigour to help compensate for the crop going in the ground later. We’ve seen consistent results over several years with the hybrid RGT Blackmoon. Equally, ensure suitable availability of macronutrients – nitrogen, phosphate, potassium and sulphur – as well as key micronutrients, so that growth isn’t hindered. Plus, there’s also a strong case for applying a biostimulant.”

With soil temperatures likely to start declining with later drilling, Andrew says this will lead to reduced mineralisation and availability of soil nutrients. Therefore, look to maximise nitrogen (N) either in the seedbed or shortly after drilling, while complying with any N restrictions, he points out.

“In addition, starter fertilisers placed under the seed, such as Microstar Actif Bzn, which supply both water-soluble phosphate (P) and protected phosphate that stays available to the plant, will help to kickstart early root expansion.

“Root growth slows down in cold, wet soils. So adding an early foliar phosphite treatment, such as Incite at the cotyledon to 2-leaf stage, will help to trigger lateral rooting and the overall nutrient scavenging ability of the plant.

“Meanwhile, potassium (K) and sulphur (S) are important for the efficiency with which the plant is able to use the N that’s available. The treatment Fulvivex contains key nutrients, especially K, but also 62% fulvic and humic acids which help to ensure K reaches the plant in a bioavailable form and which also have a biostimulant effect. Consider applying this at 6-8 true leaves.

“Boron is also critical. Fast-growing OSR consumes it rapidly, and deficiency can lead to hollow stems, vascular collapse and stem splitting. Apply foliar boron from the 2-4 leaf stage to maintain stem integrity. Fulvivex also provides some boron,” he adds.

Other key nutrients for WOSR during establishment and at the 2-4 leaf stage include molybdenum, which is crucial for nitrate reductase efficiency, enabling the seedling to convert absorbed N into protein more rapidly, explains Andrew, and manganese and zinc, which support photosynthesis and root growth. Unconsolidated seedbeds are prone to deficiency, he points out.

“Nutrition alone cannot overcome poor soil management. So it’s also important to achieve a soil pH of 6.5-7.0 to reduce lock-up of key macro- and micronutrients, and to make sure compaction is addressed to allow roots to access nutrition and water efficiently.

“Where possible, leveraging the benefits of organic manures is also encouraged. Not only can they feed the plant with essential nutrition but also improve soil biology. Their benefits can be further improved with the use of foliar nutrition and biostimulants.”