Advice on four potential agronomic tasks in August
Andy Goulding highlights how moisture is critical for some key agronomy jobs during August
Crop Progress
Winter barley harvest started in early July, but for the next couple of weeks the weather has put paid to too much progress. There are plenty of crops that are ripe as we enter the second half of July, but it’s been a delayed start and opportunities currently don’t look that good for at least the next 10 days.
Andy’s agronomy tips for August
1) Moisture is the key driver for oilseed rape establishment
Most growers are keen to drill almost any oilseed rape crop early when they have the opportunity to do so, and I don’t see that being any different this year.
Moisture, though, is the key driver for a successful start, and I’ve seen failed crops in the northwest before because it has been too dry. With the rain in July that currently doesn’t look to be an issue, but it can soon change.
The best rule of thumb is the less cultivation you can do, the better to retain moisture. The more passes with cultivators, the more likely to dry the soil, and you have the risk of it not wetting up again at this time of year. But it will depend on what challenges you are facing – for example, if you’ve had poor control of brome you may want to plough.
Varieties with good early autumn vigour are important, but also consider the earliness of regrowth in the spring. Flea beetle doesn’t tend to be as big an issue in this region as in others with the longer rotation and lower area, but early regrowth in the spring can help provide good soil coverage reducing pigeon landing sites. Pigeons are more the oilseed rape grower’s nemesis here.
2) Compromises might be needed with post-harvest stubble management
Grassweed control, especially bromes, was poorer than many hoped probably as a consequence of late applications of spring contact products such as mesosulfuron, and conditions at application that weren’t in favour of best efficacy.
That might mean there could be mixed populations of grassweeds that will need managing in different ways. Some species might need cultivation soon after harvest while for others leaving seeds on the surface for a few weeks to mature before cultivation will be better.
That could lead to compromises being required in management, although moisture is again key for germination of weed seeds. If you have little or no moisture, there’s not much point moving soil until you have some.
Where there is sufficient moisture, and you have species such as black-grass, Italian ryegrass or sterile brome, shallow cultivation to about 5cm depth should help stimulate germination, ideally with some consolidation of the surface afterwards. Effectively you’re just mirroring what you would do to get grass seed to germinate.
If there’s an early flush of 1-3 leaf grassweeds and time for a second stale seedbed, then spraying off with a minimum of 720g/ha of Roundup (glyphosate), before a second cultivation to encourage a further flush might be possible before drilling.
3) Plant cover crops
Cover crops are perhaps less popular in the northwest than further south, with less opportunity to successfully establish them. But with potential payments available through Countryside Stewardship and the Sustainable Farming Incentive some growers might be considering trying them.
The key is to get them established in August – although that might be tricky if harvest remains delayed and catchy – and into moisture. They need treating just like any cash crop. Many species have small seeds, so need a well consolidated seedbed with good seed to soil contact to get them up and away.
4) Humidity in crops will drive blight pressure
The indicator for higher risk of potato blight, the Hutton Criteria is for two consecutive days of a minimum temperature of 10C, with at least six hours of relative humidity above 90%, and even if air relative humidity doesn’t break that barrier, the humidity in big crops can be higher.
ADAS reported active blight being found in West Wales in mid-July, highlighting the wet and warm weather in early July was driving higher risk.
In August, attention turns from just foliar blight to tuber blight as well. Crops will be at different stages depending on market and intended harvest dates from stable canopies to dying canopies and crops being sprayed off.
Blight is risk during all these stages, and with only a couple of products available with tuber blight activity, such as Infinito (fluopicolide + propamocarb), careful thought needs to go into programme design to make sure you follow resistance management guidelines while protecting the crop.