Supported by:
In this field lab Andy Gray, a farmer in mid Devon, is keen to trial different techniques of managing a clover living mulch under his maize crop
Growing maize is often associated with soil erosion and runoff. This is partly because it is usually established using heavy cultivation, and harvested late in the year when the weather is often wetter. It is best practice to establish an overwinter cover crop to protect the bare soil after harvest, but this does not protect the soil for the rest of the year. There is often a long period when the soil is bare, especially whilst the maize is establishing, and immediately after harvest while the cover crop is germinating, leaving it open to erosion.
A perennial, clover-based cover crop, or living mulch, should:
However, maize is a very uncompetitive crop, and it is generally thought that a living mulch would reduce maize growth and therefore yield.
By trialling different methods of managing the living mulch, Andy hopes to suppress the living mulch long enough for the maize to establish, but still maintain the year-round ground cover.
The trial will last 3 years.
Year 1: Andy will undersow his maize crop with a clover cover crop at the 3-leaf stage of maize growth. Any gaps in the cover can be reseeded after maize harvest. Baseline soil carbon levels have been captured as part of a separate project
Year 2: Before maize drilling the plots will receive different treatments:
1 – heavy grazing with sheep to reduce the clover to ground level
2- herbicide treatment to knock the clover back but not kill it
3- control (no management)
The maize yield will be measured using a weigh bridge at hearvest
Years 3 & 4: repeat
At the end of the trial samples will be taken of soil organic matter and soil carbon.
Unfortunately the living mulch in teh new trial field, which was sown under the maize in July 24, has completely died. This may have been due to mechanical (ripping up the stolens) or chemical causes (glyphosate).
So Andy will undersow this year's maize crop again in July and try again.
Learnings from the last year:
Clover establishment has always been a problem: last year when they drilled it they got good coverage. But it was established too late int he year which meant that there were a lot of annual weeds coming through – specifically hemlock, groundsel, black nightshade. But Andy cannot drill the clover any earlier or it would be killed / impacted by the post emergent herbicide applied to maize.
Ideally both the maize and clover could be drilled at the same time, but the weed burden would then be a problem.
If you’re able to get rid of the weeds in year 1 with a herbicide which doesn’t affect clover, then theoretically the living mulch would then do the weed suppression for the next few years, and no need for herbicides in the following years.
This year Andy established the maize into a 1.5ha trial plot of rivendel dwarf leaved clover which had been established the summer before by undersowing the maize crop in late June. The clover living mulch didn’t look great in the winter but in early spring it really got going.
Andy treated one plot of clover with dilute glyphosate in April – it didn’t knock it back enough and it did not kill the weeds. BUT it clearly did something as the glyphosated patch had slightly better maize at harvest.
In early May Andy cultivated a 15cm strip with a strip till machine. On reflection the strip was probably too narrow as the clover closed in too quickly: a 20cm strip might be better if we can find a strip till machine to do that.
By end of May the maize was growing well with a strong tap root
There were some issues with annual weeds including groundsel and hemlock, but otherwise the crop looked good.
Up until August the maize was growing well, and the living mulch providing good ground cover.
But in August the maize growth slowed significantly as it was out completed by the clover. This resulted in a complete failure of the maize crop which was 2-3 ft rather than 8 ft in the adjacent field which was grown without the clover living mulch.
This is a great disappointment, particularly as the early months were so promising.
Plans for next year:
In spring/summer 2024 in an adjacent 4ha field Andy undersowed his maize with clover again. Research has confirmed that specialists agree that Rivendel was the best clover variety for the LM.
He aims to have 2 adjacent plots, one with living mulch, one with bare soil. He wants to include a buckwheat treatment in the trial in both plots (chequerboard layout). He min tilled buckwheat straight into clover after harvest in October 24.
The plan for May 2025 is to strip till the maize into these plots, hopefully with wider spaced rows – up to 75cm if strip till machine can do that.
We want to include micronutrient testing during the growing season to see what the maize and clover plants are competing over within the field eg sulphur? And why the clover took over so aggressively, as this might be remedied with extra micronutrient based inputs.
Anther benefit we’d like to measure is to do with N: theoretically once the maize canopy excludes light from clover there is supposed to be a clover leaf drop which should add N to the soil.
We would like to source a machine which is common in Switzerland which can do the whole establishment in a single pass: strip til, glyphosate and nutrients.
The trial fields are looking good. Andy applied glyphosate to the clover in his herbicide trial plot earlier in the year, though it does not appear to have knocked back the living mulch at all!
The maize can be seen in the bare soil rows between the living mulch. The big question now is whether or not the the clover will be too vigorous for the maize. The leaves are not quite as 'micro' as we'd hoped. However, the maize tap root has already gone below the clover, so it may get away before the clover encroaches / competes too much...
The maize has now been harvested leaving the clover living mulch in the field. The living mulch is quite patchy and parts need to be reseeded.
Once the maize reached the 3-leaf stage it was undersown with the clover cover crop / living mulch.
After a difficult few weeks in terms of weather, the maize has been drilled in the trial field
May 2023
June 2023
Sep 2023
September 2023
April 2024
May 2024
Years 2 and 3
Sep / Oct 2026
Soil Association
Bristol / South West
As the Innovative Farmers Network Coordinator, Laura engages with farmers, scientists, industry bodies and advisors to launch on-farm trials, ensure they keep running smoothly, and to share results. With an MSc in Sustainable Rural Development, Laura trained as a land agent. She then worked as a farming advisor in Devon, particularly on projects aimed at reducing diffuse water pollution in river catchments.
Elston Farm
Devon
ADAS
