Another year another (inter-) crop. But the years are so variable. More unpredictable weather affects cultivations, crop development, and harvest. With all these variables, figuring out a blueprint to grow intercropped organic oilseed rape is tricky.
A group of organic growers have been collaborating with a local processor for about 5 years now. The growers supply organic oilseed rape to produce a high value, cold-pressed culinary oil. They have found that growing a consistent, reasonable-yielding crop has been challenging. Several of the growers have used intercropping to suppress weeds and mitigate pest damage. But there hasn’t really been enough time and enough crops to identify what consistently works. Yet.
It is now late spring. And the crops are generally looking good. Here is a snapshot of what SRUC (Scotland´s Rural College) and SAOS (Scottish Agricultural Organisation Society Ltd), IntercropVALUES partners, have observed.
North
The farmer aims to sow peas into this crop. It is currently a monocrop. It looked great. It was clean, with little disease or pest damage, had a good crop cover, and was in full flower. Why did it look good?
- Sowing date. The crop was in by the end of the first week of August.
- Fertility. The crop followed grass, which left residual nitrogen in the soil. As well as hen manure, which had been ploughed in before the crop was sown.
- Little weeds. Following good establishment. Interestingly, the areas that had (unintentionally) not been rolled looked better than the rolled areas.
South
Further south, the crop didn’t look so promising. It was quite patchy. The plants had just reached bud stage and these buds had the odd pollen beetle on them. Raising concerns about yield potential if their numbers increased. But, amongst the weeds some small-leaved white clover was emerging, which will fix some much-needed nitrogen for the crop. What were the factors that led to the crop looking like this?
- Late sowing – in late August. The farmer has found that ploughing in May and then sowing in early August is more likely to result in a good crop.
- Pigeons. The bird-scarer (the ‘banger’) didn’t work all the time.
- Fertility. The type of organic farming practiced does not add nutrients to the soil. Which limits crop yield. In the past, the farmer applied organic hen manure in late summer.
- Beetles. The farmer has found that organically approved garlic spray reduces pollen beetle numbers, but this type of farming does not permit its use.
Top tips
- Sow early. Plough out grass or a cover crop in early summer to make early August sowing more achievable.
- Spray garlic. An expensive but reasonably effective way of limiting pest damage for a high value crop.
- Try sowing spring cereals in the mix around field margins. The growers think this deters flea beetle, a damaging crop pest.
- Don’t roll after sowing. Maybe! Leaving soil loose minimises weed establishment, but it can make slug damage worse. We have had a dry spring in Scotland this year, with low slug pressure. Consider what your biggest potential problem is.
- Apply manure. Oilseed rape is a hungry crop that responds well to fertiliser.
- Using home-saved seed is fine. And cheaper.
This news article was written by David Michie, from SAOS.
Images by Robin Walker (SRUC)