Ty Coch Project Update - Final Update
Key results:
The greatest biomass of 20t/ha was seen in plots that included mixes of cover crops, with the greatest number of species and especially those that were broadleaved.
The plot which was not undersown had the lowest yield, with a yield of 7.2t/ha less than the plot which had been undersown but had the lowest yield.
None of the mixes improved the soil nitrogen levels, although a wet winter could have contributed to this. Nevertheless, the least nitrogen was seen in the plot which had not been undersown, suggesting that undersowing of maize does help limit some leaching of nitrogen.
Background:
With nearly a third of the farm sown into arable each year, the Bowyer family were keen to explore ways to protect and enhance soil health. The integration of cover crops following cereal harvests offers a strategic method for enhancing soil health and achieving long-term agricultural sustainability. The aim therefore was to trial different seed mixes for undersowing maize and also for cover cropping over winter following cereals.
Purpose of the work:
Establish a suitable cover crop mix to follow cereals which would provide a break crop, fix nitrogen for the subsequent crop and provide suitable grazing for sheep.
Establish a suitable undersown mix for maize which could potentially be beneficial to support soil structure, nitrogen retention and reduce the risk of winter soil erosion.
Maximise the farms capacity to store carbon and promote biodiversity.
Provide options for farmers to consider as alternative cover cropping solutions.
What we did:
All fields were tested for soil nitrogen and organic matter.
Cover cropping
The field was drilled on 23 August 2024 which involved the plots being power harrowed, seed spun on using a fertiliser spreader, and then the seed was power harrowed back in. The 6 different one-acre plots consisted of:
Plot 1 - Winter Oats 80%, Winter Vetch 20%
Plot 2 - Vetch 17.5%, Berseem Clover 7.5%, Winter Oats 70%, White Mustard 5%
Plot 3 - Balansa Clover 10%, Tillage Radish 20%, Winter Oats 27.5%, Vetch 27.5%, Phacelia 5%, White Mustard 10%
Plot 4 - Untreated (control)
Plot 5 - Linseed 15%, Buckwheat 15%, Phacelia 5%, Tillage Radish 15%, Fodder Radish 15%, Brown Mustard 10%, Vetch 15%, Crimson Clover 10%
Plot 6 - Berseem Clover 15%, Vetch 85%
On 21 January 2025 the biomass of each plot was recorded, along with taking soil samples for nitrogen and soil organic matter.
Undersowing maize
The maize variety Foxtrot was drilled on 25 May 2024. It was sprayed on 25 June 2024 with GYO 0.75l/ha (AI Pyridate) and then due to weed issues it was sprayed again on 4 July 2024 with Barracuda 0.75l/ha (AI Mesotrione). The contractor undersowed the maize whilst it was no more than knee high. It was drilled on 17 July 2024 using the Usk and Wye Foundation Drill, which is a more purpose-built Weaving drill. The maize was harvested on 14 October 2024 and the dry matter and yield was recorded for each plot. The 6 plots were:-
Plot 1 – GFS Megayield (50% Westerwolds & 50% Italian Ryegrass) drilled at 15kg/acre
Plot 2 – Untreated (Control)
Plot 3 – 85% Spring Oats & 15% Red Clover drilled @ 6kg/acre
Plot 4 – 50% Strong red creeping Clover & 50% Italian Ryegrass drilled @ 6kg/acre
Plot 5 – 10% Gorilla Forage rape, 45% Italian Ryegrass diploid and 45% Italian Ryegrass Tetraploid drilled @ 6kg/acre
Plot 6 – 90% Spring Oats & 10%Forage Rape drilled @ 6kg/acre
Outcomes:
Cover crops
All of the species emerged in all of the plots, so establishment was very successful with the plots continuing to grow well over the winter months. Due to the field not being sprayed with glyphosate before planting there was volunteer barely emerging meaning that the ground was not bare in the untreated plots.
Prior to drilling the soil nitrogen levels were 40kg/ha and the organic matter was 4.7%.
The biomass of each plot was taken on the day of harvest by taking the fresh weight of a 1m quadrant above ground, table 1.
Table 1. Biomass data for each plot.
Plot | Biomass (kg) | Biomass (t/ha) |
1 | 0.9 | 9 |
2 | 1 | 10 |
3 | 2 | 20 |
4 - Untreated (control) | ||
5 | 2 | 20 |
6 | 0.5 | 5 |
The highest biomass was seen in plots 3 and 5 which had the largest number of broadleaved species in the mixes.
On the day of harvest the soil nitrogen levels and organic matter were tested from each plot, table 2.
Table 2. Soil Nitrogen and Organic matter levels
All the nitrogen levels had decreased therefore none of the mixes had maintained or improved the nitrogen levels in the soil. However, it must be considered that a very wet winter was had during this project and may have contributed to the reduction. The cover crops would also have taken up soil nitrogen during the growing process, and it would have been expected that mixes with the highest biomass would have utilised more nitrogen, reducing the prospect of runoff into watercourses.
It was also not possible to be definitive about any effects of the cover crop mixes on nitrogen in the soil as the untreated plot ended up not being as bare as originally planned. No significant changes were seen in the soil organic matter, but out of all the plots plot 1 showed the highest soil organic matter of 5%.
Undersowing maize
All plots emerged within 7 days of drilling with all species drilled successfully emerging, including the clover.
The yield for each plot was taken on 14 October 2024, table 3.
Table 3- Yield data for each plot.
The greatest yield was seen in plot 3, with a yield of 21.1t/acre. Although this could be an anomaly as the red clover did not survive and the oats did not produce a large amount of ground cover. The lowest yield was in plot 2 with 12.2t/acre, which was the plot that had not been undersown and this was 2.9t/acre less than the lowest yielded undersown plot.
In January 2025, the plots were tested for nitrogen and organic matter. All of the plots had less nitrogen in the soil than before the maize was planted, suggesting that minimal nitrogen fixation had happened with the different mixes used for undersowing. However, it was interesting to see that plot 2, which had not been undersown had the least nitrogen in the soil at 2kg N/ha suggesting that the undersowing of plots does help to limit some leaching of nitrogen. The organic matter had risen slightly in all plots, however not by a significant amount.
From the undersowing of maize trial, we can conclude that the best mixes to use when undersowing maize are still the grass mixes using IRG and Westerwolds. During this project, the clover was significantly affected by the chemicals required for weed control and the rape affected by slug damage. The oats grew well although a higher seed rate may have been beneficial to allow some tillering and more ground coverage.
How to apply on your farm:
Take soil samples of the field to correct any imbalances pre drilling.
Consider using glyphosate before planting if you do not want to risk having volunteer seeds appearing in your cover crops.
Decide on a suitable cover crop mix/ undersown mix to meet your needs.
Correct timing of seed drilling is important for optimal establishment success.