Thursday, 25 February 2021
Recently, spring cereal and oilseed crops have become more common in the arable rotation. AHDB’s head of the Recommended Lists (RL), Paul Gosling, investigates some of the key considerations when thinking about the switch from winter to spring options.
The recent rise in spring cropping areas has been partly fuelled by difficult autumn drilling conditions and, in some areas, high black-grass pressure. In addition to weed management benefits, spring crops can also assist with the cultural control of some major pests and diseases. Put simply, they can bring many aspects of integrated pest management (IPM) into control programmes.
Targeted use of cover crops
Overwinter cover crops, followed by a spring cash crop, are an attractive option for those wanting to improve soil conditions. They also offer many other benefits, such as increased biodiversity and nutrient retention. AHDB and numerous organisations have conducted extensive work on cover crops, but the key is deciding what you are trying to achieve with them. This will determine the species to use and their management.
While cover crops are a key attraction of spring cropping for some, black-grass control is the driver in many of England’s black-grass hotspots. The long window between harvest and drilling a spring crop gives multiple opportunities to control flushes of black-grass. In fact, spring cropping is the single most effective cultural method of reducing black-grass populations, offering up to 96% control. When using glyphosate though, it is important to remember that there is a real danger of resistance to glyphosate developing in black-grass, so cultivations should be combined with any use of glyphosate to reduce the chances of selecting for resistance.
While around 80% of black-grass germinates in the autumn, there will be some that germinates in the spring. Where populations are high, this can mean significant numbers. So, when choosing a spring crop as part of an IPM approach to black-grass control, it is important to select a competitive crop, especially as herbicide choices are limited. Spring barley is the most competitive, followed by spring wheat. For spring cereals, seed rates need to be higher, because they do not tiller as strongly as winter cereals. This also helps suppress any germinating black-grass.
Considerations for spring cereals – costs, markets, diseases and pests
Generally, spring crops yield less than their winter counterparts, but input costs are lower, with cereals often requiring just one or two fungicide applications. Although premiums may be available for milling wheat, it is important to check with your local miller/merchant to ensure you grow a variety that they will accept.
Spring barley is the other obvious cereal choice, with a potential premium for malting. However, premiums have slipped due to a decline in demand during the coronavirus crisis and greater areas grown.
Our recent ‘Analysts Insight’ on spring crop margins is also well worth reading – this shows the strongest margins for spring milling wheat, followed by spring malting barley.
If you opt for spring wheat, it is worth noting that it can be more susceptible to ergot than winter wheat. Ergot risk is higher where flowering is extended, so establishing an even crop is important. Fields with a known ergot history can be ploughed after an infected crop to bury sclerotia to reduce risk – this is because sclerotia do not remain viable for long in the soil. Conversely, take-all risk is lower with spring wheat.
Any spring cereal sown before April is also more vulnerable to wheat bulb fly. On the other hand, later-drilled crops may be more prone to gout fly. These pests need to be taken into consideration, especially in high-risk situations. Seed treatment is available to give some protection against both pests (depending on when you drill).
If orange wheat blossom midge (OWBM) has been a local problem, a resistant variety is a good bet, as timing of sprays is tricky. Mulika, KWS Cochise and KWS Chilham are varieties on the current RL with OWBM resistance.
Considering spring oilseeds?
The area of spring oilseeds grown in the UK is not high. However, like spring cereals, they are a low-input alternative to winter cropping. When using the RL to select spring oilseed varieties, you need to remember that these are Descriptive Lists. These use a smaller number of trials, compared with the Recommended Lists, and the difference in yield between varieties is often not statistically significant.
Variety options for spring oilseed rape have increased this year, with Clearfield varieties now included on the list and even a clubroot-resistant variety.
A drilling date of late March or early April allows a good window for black-grass control. Later dates risk yield reductions and earlier drilling into cold seedbeds is not advised.
Cabbage stem flea beetle (CSFB) is not a problematic pest in spring oilseed rape. However, more attention needs to be paid to pollen beetle. These can devastate spring oilseed rape. In fact, some of our spring oilseed rape variety trials have been lost due to pollen beetle. As a result, checking for pollen beetle, from four to six weeks after the crop has emerged, is important. Treatment thresholds exist and many pollen beetles are now resistant to pyrethroid sprays, so treatment should only be applied when necessary.
Spring linseed is unrelated to other crops in the arable rotation and offers a good pest and disease break. It is uncompetitive against weeds but has a fairly wide drilling window – mid-March to mid-April, even May, with sufficient soil moisture. This means drilling can be delayed where black-grass is an issue, allowing more control opportunities. Pre-emergence herbicides are important for weed control, but there can be issues with crop safety with post-emergence herbicides, particularly if the crop is drought-stressed. The main pest issue with spring linseed is adult feeding damage from the flax flea beetle. It is a different species to cabbage stem flea beetle and is susceptible to pyrethroids.
When it comes to winter-v-spring cropping decisions, there is certainly a lot to consider. Our Knowledge Library is an excellent source of information – including in-depth guidance on all of the topics explored in this blog.