Autumn Drilling

With harvest now over and the weather starting to feel decidedly Autumnal I thought it would be worth posting on the topic of Autumn drilling. The rains have arrived to provide adequate soil moisture for cultivations and the temptation may be there to consider drilling soon. Certainly, this can be a positive thing for the crop with the warm moist soils providing excellent conditions for fast germination and establishment and allowing the crop to develop bigger roots and more biomass ahead of winter. Warm moist soils will have higher nutrient availability which will also allow the crop to get off to a strong start and will help to capture more nitrogen in the crop ahead of winter, reducing leaching. The later drilling is left, the slower emergence is, with a typical requirement for cereals of around 150 degree days from sowing. The typical mid-October sowing time for organic generally means crops won't emerge until November. Establishment declines the later drilling is left and tillering capacity is also reduced. These are key reasons why seed rates must be increased the later the sowing. Of course, the risks of deteriorating conditions later in Autumn and the possibility of not being able to drill will always provide an incentive to think about sowing earlier.

Early sowing can be expected to deliver higher yields under non-organic conditions since the risks created by early drilling such as pests, weeds and diseases are generally easier to manage than for organic farmers. The main risk for early drilling in Autumn is the potential for increased weed pressure, with less opportunity to utilise stale seed bed techniques. Providing good conditions for the crop to grow also provides weeds the same opportunity. Depending on the particular weed burden and community and on your in-crop weed control method, early drilling might not be the most suitable option as the increased yield potential could be easily lost through more weed competition.  If drilling competitive crops, with good early vigour and using higher seed rates to provide good ground cover, some level of weed suppression should be possible. The work carried out under LiveWheat showed that the wheat variety Extase with a shorter growth cycle and strong early vigour was able to suppress weeds compared to less vigourous cultivars. Recent innovations in intercropping with frost susceptible nurse crops or the use of clover living mulches may help to adapt Autumn sowing earlier or later, providing increased flexibility.

Under organic farming conditions, higher seed rates are generally recommended. The risks from disease and lodging are reduced by the lower nitrogen supply without the use of mineral N fertiliser. In addition, without fungicidal and insecticidal seed dressings the risk of lower emergence is possible and without herbicides to manage weeds, higher seed rates to compensate for lower germination and increased crop competitiveness against weeds can be a good strategy.  Of all the yield components of an arable crop, plant population is the most significant, especially under lower nitrogen environments where tillering is limited and productive tillers rarely number more than one, starting with a high plant population should provide the foundation of a good yield, although crops can compensate for lower plant populations, this compensation is limited under organic conditions.

Another consideration is the use of the growth promoting seed dressing Tiros, which contains endophytes, a consortium of microorganisms that live inside the plant cells, helping provide additional nutrients and resilience against biotic and abiotic stresses. Farmers who use it report anecdotal evidence of enhanced crop growth, and at approximately £60 to treat a tonne of seed, is potentially a cost-effective way to help improve crop germination, establishment, increase root mass, enhance nutrient uptake and protect the crop against abiotic stress including drought. It could be worth running a small on-farm trial looking at Tiros treated seed against an untreated control to see if we can provide hard evidence of the benefits of its use.

One thought that has often struck me whenever I see double drilled areas in a field around the margins is just how much additional groundcover this provides which as we know really helps with weed suppression. I know there are probably many practical and logical reasons not to cross drill, including the additional time and not least because it stops you being able to mechanically weed the crop, but with the enhanced ground cover it provides, this might be less necessary anyway. I would consider dropping seed rates within row to 75% so that in total you have 150% of your typical seed rate, with reduced competition within row. I'd be interested to hear our members thoughts on this technique, particularly if taking a very low input approach to in-season crop management.

As always it would be fantastic to hear from you about your own thoughts and experiences on Autumn drilling approaches so, please get in touch or post a comment below. In the end, many years of experience and trial and error have led to the status quo, but agroecology means continuing to research, to test and to fine tune to find the best approach suited to your own system.