Finding practical solutions is at the forefront of the programme of research and trial work at Germinal Horizon Wiltshire. Farmers, as land managers, juggle managing pests, weeds, diseases, tightening regulations and increased demands on production alongside attempting to implement sustainable practices.
That’s where vital Germinal Horizon research and data are bridging the gap – using research to identify workable sustainable farming methods that will help farmers adapt to climate challenges and reduce their environmental impact without compromising production.
At Germinal Horizon Wiltshire (GHW), the technical trials team has confirmed that by undersowing maize over a two-year period, farmers can achieve a similar yield and crop quality while also gaining sustainable farming benefits by protecting soil through winter.
In 2023, GHW completed their two-year trial assessing the viability of undersowing maize with grass and clover varieties. This trial assessed the environmental impact of leaving land bare and soil exposed over winter once maize had been harvested in autumn.
Establishing an understory
In the trial, maize was undersown with grass, clover, and a combination of both using Tom Lands’ specialist inter-row maize drill – Landwrx. The inter-row drilling operation was carried out when the maize was at 4-6 leaf.
Measuring maize yield
In the trial, maize was undersown with grass, clover and a combination of both. Overall, what we found was that maize undersown with the most vigorous understories would typically produce lower yields (0.725t DM ha-1) in the first maize harvest.
In other Horizon trials, there have been no adverse impacts on the initial maize yield for the addition of an understory. However, when resown with maize the following spring the nitrogen released from the grass breakdown would then elevate the second maize crop to produce an overall yield matching or elevated production over the maize that wasn’t undersown.
Looking at yield, the fallow maize plot outperformed AberChoice and AberNiche in year one, producing 17.558 t DM ha-1. However, the fallow maize plot was outperformed by five other undersown species. Importantly, over two years, adding an understory did not significantly impact the total maize yield.
Weather challenges
During the trial, the 2021 total rainfall of 583.56 mm was less than the 10-year average of 770.84 mm, and then the 2022 total rainfall fell to 325.27 mm. Meanwhile, the average minimum temperature in July 2022 also swayed from the 10-year average, increasing by 5.73°C and further highlighting how UK weather patterns have changed in just a decade.
| Undersown species | 2021 yield (t DM ha-1) | 2022 yield (t DM ha-1) | Total yield (t DM ha-1) |
| AberChoice + Aran | 18.416 | 11.082 | 29.50 |
| AberRoot | 18.178 | 10.878 | 29.06 |
| AberLasting | 18.009 | 10.756 | 28.76 |
| Aran | 18.125 | 10.423 | 28.55 |
| AberChoice + AberLasting | 18.246 | 10.118 | 28.36 |
| AberChoice | 16.903 | 11.447 | 28.35 |
| AberNiche | 16.711 | 11.394 | 28.10 |
| Fallow | 17.558 | 10.517 | 28.08 |
Source: Germinal Horizon Wiltshire
Examining maize quality
The fallow maize plot performed better when measuring metabolisable energy (ME). After leading in year one, fallow was overtaken by AberChoice with Aran, delivering an average quality of 10.995 MJ/kg. Finishing closely behind were AberChoice with AberLasting, AberLasting, and AberRoot.
| Undersown species | 2021 ME (MJ/kg) | 2022 ME (MH/kg) | Average quality |
| AberChoice + Aran | 9.58 | 12.41 | 10.995 |
| AberChoice + AberLasting | 9.67 | 12.09 | 10.880 |
| AberLasting | 9.76 | 11.95 | 10.855 |
| AberRoot | 9.75 | 11.83 | 10.790 |
| Aran | 9.69 | 11.61 | 10.650 |
| AberChoice | 9.09 | 12.18 | 10.635 |
| AberNiche | 9.14 | 11.88 | 10.510 |
| Fallow | 9.83 | 11.95 | 10.890 |
Source: Germinal Horizon Wiltshire
Ground cover
Our research shows that some undersown species can compete well with fallow maize for yield and quality over two years. One of the main benefits of undersowing discussed is the reduced bare soil over winter.
The AberChoice and AberNiche containing understories demonstrated the highest ground cover percentages post-harvest of the 2021 maize crop. Even a singular variety like AberNiche can offer 26% ground cover, while AberChoice with AberLasting can provide as much as 31%.
Source: Germinal Horizon Wiltshire
The multiple benefits of undersowing maize
By undersowing maize, farmers benefit not only from increased soil protection in winter but also gain an additional forage source when the land would otherwise be fallow following harvest.
As GHW research shows, there are species combinations that will produce similar maize yield and quality over a two-year period. Boosting soil health, having additional grazing and reaping wider environmental benefits means undersowing maize can be a productive practice for livestock farmers.
Subject to meeting specific conditions, English and Welsh farmers have the added advantage of claiming government payments for this practice, which can protect soil and provide a habitat that benefits animals and birds that forage within the undersown cereal crop.
Undersowing maize payments in England
Depending on eligibility, English farmers can apply for the SW5: Enhanced management of maize crops scheme with payments of £203 per hectare subject to a maize harvest before 1st October.
The Sustainable Farming Incentive (SFI) scheme offers a number of other options, including SOH2-4, providing payments for establishing multi-species cover crops in spring, summer or winter. SOH2-4 can also be combined with CSAM2 and integrated pest management actions (IPM1, 3, 4), but please seek professional advice to claim multiple actions successfully.
Undersowing maize payments in Wales
For Welsh farmers, there’s a grant of £91 per hectare up to £5,000 for farmers who undersow maize with a cover crop. The mixture must be sown by 10th July and include at least two crop species suitable for growing in the shade of maize.
Ask the forage experts
If you’re interested in undersowing maize, contact a Germinal expert to discuss mixture options and management.