Should you be undersowing maize?

Should you be undersowing maize? 

Agrovista Agronomists Dan Knight and Phil Campion, along with Head of Rural Consultancy Phil Edenborough, as they discuss undersowing maize. Covering the benefits to growers, how to practically achieve successful undersowing, and any potential support available.

  • Grass mix - what mix we use and why we use it
  • Soil health and environmental benefits of undersowing maize
  • Potential available grants and financial support for those deploying undersowing maize techniques
  •  Look at sowing methods and discuss experiences

Paul Robinson - Undersowing maize

Richard Pilkington - Dairy and sheep farmer

Tom Fowles - Contractor and dairy farmer

The spacing you recommended was 15cm 2 years ago, what has changed?

Earlier work was at 15cm but we found there was a higher risk of crop competition, so the recommendation was increased to 25cm, this also suited the machinery being used on 12.5cm spacings. The distance between the maize and the cover crop within the row should be wide as possible whilst considering the balance of how much cover we want to achieve after harvest.

Interesting to see a Mzuri drilling maize. Is there a case that maize can be drilled sufficiently with a strip till drill? I know it’s off topic, apologies!

Yes there is a strong case, particularly if under-sowing, wanting to improve soil health and reduce establishment costs. Adapted mzuri drills to drill the maize, under-sow and placement fertiliser are out there. However, if reduced cultivations or strip till is adopted, greater attention to detail will be required to ensure maize yield is not detrimentally affected. Monitoring for compaction, reducing trafficking as best as possible and maintaining a growing cover before entering the maize crop will be all key parts the system.

We are moving toward strip till cultivating before drilling, how do we drill the grass seed into that firm area?

It would depend what system is used, machinery available, soil type and condition; with all 3 influencing the final decision. It may be favourable to be drilling grass seed in a firmer seedbed particularly on lighter soils. If the seedbed is unlevel or compacted this would obviously need some remedy work. Thoughts would need to be made around whether a tine followed by a packer wheel or Cambridge roll would provide consistent enough results and if not the use of a suitable coulter for placement.

Does the time you sow change how vigorous the grass should be (e.g. PRG for later drilling) and the method that you use for establishment?

Yes very much so and seed rate. SoilMax is developed for at drilling partly due to its slower development. As you move to 4-6 leaves move to EnviroMax to give more vigour from the perennial ryegrass and desired cover prior to maize canopy closure. Italian ryegrass could possibly be used at the later stage closer to 6 leaves but beware results are inconsistent and root mass will be inferior. If you get beyond 6 leaves this is the point to have the conversation on whether to save the money and not under-sow to avoid disappointing results.

Can you explain a bit more about your disc drill, would this drill through samco film? There are numerus growers with maize grown under film wanting to undersow

Up until now, we have not done any work with under-sowing grass into maize grown under film. Using the weaving coulter to under-sow directly into film need investigating. However, for 2021 development we will be assessing a new drill that establishes maize under film in single rows and this is anticipated to allow under-sowing in between the maize rows either at drilling or at 4-6 leaf stage.

Cost of drilling? Cost of seed mix?

The cost of drilling will depend on whether the drill being used is farmer-owned, or provided by a contractor etc, and will vary according to previous cultivations, soil type etc. Likewise, the cost of the seed mix will depend on the seed rate being used. Generally, seed costs would range from £12-£20/acre. Obviously, both these direct costs can be offset with any catchment or stewardship funding available, not to mention the added benefits to retained nutrients, soil health, extra grazing and achieving compliance etc.

Corn borer is becoming a big concern how do you manage that in this system?

Yes, corn borer is a big growing concern and is already an issue in the south of England. The under-sown system will provide both a habitat for Beneficial’s and corn borer alike, so the jury would be out at the moment as to who wins out in that battle. It will be likely that if the problem continues to grow there may have to be some fundamental changes to how we grow maize in this country with a greater focus on IPM and who knows, a greater emphasis from plant breeders for the UK.

How do we find out which contractors have these specialist machines?

Ask around. Speak to your local Agrovista agronomist and speak to contractors to express your interest. You don’t have to go far to find someone who has one of the two systems in use. Clearly if maize under-sowing is to become the norm there is going to have to be an increase in machinery available to meet the demand. Some will decide to purchase or modify their own machine but if contractors know there is a demand from customers it usually isn’t long before they deliver the service. Some guidance will be needed early on as the system will require some knowledge from the drill operator or grower to avoid any disasters. But with clear communication and involvement from your agronomist from the planning phase should prevent any of this happening.

Typical cost per ha of a contractor applying inc seed?

The cost of a contractor under-sowing maize will depend on the timing of under-sowing. If the mix is under-sown at the same time as the maize, this saves the cost of an extra pass later in the crop, but this will be offset by the extra time needed/reduced work rate associated with doing this at the same time as drilling. A typical contractor charge for under-sowing at 4-6 leaf stage may be anywhere between £30-50/ha depending on distance travelled, field sizes, work rates etc. This figure would not include grass seed.

If you are putting field into winter wheat straight after maize is it worth under sowing maize?

Potentially yes, because it will still be stabilising soil, retaining nutrients ready for the following crop, and will help towards reducing damage from harvesting traffic. We have successfully direct drilled winter wheat into under-sown maize stubble in October. As mentioned in the presentation, the best rotational crop plans can soon be undone if the autumnal weather turns for the worse after maize harvest, and before you get the wheat in; if this happens at least there is a ready-made cover already established to avoid a bare stubble over-winter. This should also provide better soil conditions ahead of the spring crop.

How much N can you safely put down the spot?

RB209 fertiliser guidelines state that up to 10-15kg ha of the total nitrogen requirement may be placed below the seed at drilling. Many growers may already be putting on more than this, but we would always advise that you consult a FACTS qualified advisor to come up with a fertiliser recommendation based on your individual situation.

Have you any data on the starch % / starch yield of the maize crop - conventional vs undersowing?

We haven’t got any results from our trials, but a recent United Utilities trial in 2018 where they took samples of fresh and ensiled maize from plots that were conventional vs under-sown showed there was no significant difference for dry matter, metabolizable energy, starch or crude protein. But this was only one trial in isolation. It is something that needs to be looked at in more detail in future trials.

On high pH soils, could legumes / clover help make phosphate more available to the maize crop? I would be very interested in knowing if this has been looked into.

In short no, we have not specifically looked directly at this. Having looked at clovers in mixes over the years we have not seen any cost benefit to them in this system. They either poorly establish or fail to develop enough. There could be a case for species diversity, but I think we can get this into the rotation by more cost effective means. Having said that it would be a challenge to see if we could establish a semi-permanent white clover cover in a rotation! We are however closely looking at how we can make better use of soil bound phosphate by making it available for maize uptake given its importance for early crop development with the use of phosphate liberator at or just after drilling. On high pH and calcareous soils phosphate is being locked up as calcium phosphate and it isn’t beyond possibility that applications of fresh phosphate may become restricted where soil indices are already high. It’s a really good example how we are striving to use new technology to improve resource efficiency, resulting in profitable crops with a lower environmental impact.