With the mild autumn and good establishment, oilseed rape crops are looking good across the country. However, while forward or large canopies can seem beneficial, if not properly managed they can limit yields and leave the advantage of good establishment underutilised.
Here are 5 top tips for how you can capitalise on a forward oilseed rape crop:
1. Measure and quantify the canopy. You can manage what you can’t measure. An oilseed rape canopy contains nitrogen which can be remobilised by the plant. Using GAI apps or satellites, you can measure the green leaf area in relation to the ground. 1 GAI is equal to 50 kg/ha of nitrogen. Or, cut 1 m² of above-ground biomass; 1 kg equals 55 kg N/ha.
2. Reduce the first split of nitrogen. High doses of early nitrogen encourage rapid stem elongation, causing shading and plant competition. This leads to lower branches aborting—branches that have the capacity to hold the most pods and yield.
3. Aim for a GAI of 3.5 at flowering. This is equivalent to 175 kg of N/ha in the canopy. Using knowledge of what is already in the crop can help save on nitrogen input. AHDB report PR447 suggests only 60% of spring-applied nitrogen is utilised by the crop, so adjust rates accordingly.
4. Don’t delay sulphur availability. If using products such as DoubleTop®, reducing nitrogen also reduces sulphur. Lack of sulphur can be yield-limiting: slowing leaf and tissue development, reducing nitrogen-use efficiency, lowering stress tolerance, and reducing oil content. Pick a product that applies 40–75 kg/ha of SO₃.
5. Apply micronutrients early. In particular, Boron, as low levels can result in stem splitting during rapid spring growth, allowing potential entry for disease. Boron is also key for good pollination and stress tolerance.
