Putting clover living mulches to the test

A team of six farmers is aiming to discover whether cash crops can be successfully grown in a permanent clover understory, or living mulch, in order to control weeds and fix nitrogen.

A key question is whether this can be achieved without significantly affecting yields.

The group is made up of organic farmers and conventional no-tillers and although both farming systems can learn from each other, the challenges for each of making an alternative system work are quite different due to the respective starting points.

The trial is part of the living mulch field lab being run through the Innovative Farmers programme with the support of AHDB, Organic Research Centre and Organic Arable.

James Alexander hosted a field walk last month to show the results of the trials so far at the 600-hectare arable enterprise he runs in Oxfordshire, of which just over half is organic.

The conventional land has been under a no-till regime for 17 years now.

Production However, Mr Alexander hopes that the work he is doing alongside Innovative Farmers could help him reduce cultivations in his organic crops as well.

The organic side is currently power-based but we want to move away from that. Currently we have to take one-third of the organic land out of production every year for clover leys, so we are losing a lot of productivity. If this works, we could get rid of that fertility building phase and just drill directly into it.

Both organic and conventional plots were drilled with clover on the same day in May last year into spring barley just before T1.

At harvest, the organic spring barley saw a very slight increase in yield, which Mr Alexander suspects was down to the clover underlay.

However, in the conventional crop the clover failed to establish.

Mr Alexander said: We used the same drill and organic matter levels are the same in both fields, but I think we had a stronger conventional crop which outcompeted the clover.

Microleaf seems harder to establish so it might be bigger leaves are easier.

This season, Mascani oats were direct drilled at 400 seeds/sq.m into the clover using a Cross Slot drill in the third week of October.

Outcompeting Crops in the field, which is on Cotswold Brash and 293 metres above sea level, are around three weeks behind in growth following the cold spring, but oats cropped with clover appeared darker, taller and stronger compared to the farm standard.

Other growers in the group agreed the same could be said for their crops.

One concern for the clover understory is management to stop it outcompeting the cash crop, particularly in organic scenarios where herbicides cannot be applied.

Mr Alexander said: It just sort of sat there all summer but after harvest the clover erupted with growth but we didnt graze it.

I dont know what Ill do this winter yet we need to get the balance between smothering the weeds and not outcompeting the crop.

Competitivity could also be an issue for the clover crop said Dominic Amos, senior crops researcher at the Organic Research Centre, because there is a theory that when clover is putting energy into stem growth, it has less energy to put into nitrogen fixation.

Another grower in the group, Mark Lea, who runs a 180ha organic sheep and arable farm in Shropshire, said he sees sheep as the only way of managing the clover in organic systems, adding that if weeds can be suppressed through the clover, delayed drilling might not be so critical and could potentially be brought forward to early October.

Mr Lea established his living mulch into sandy loam and has direct drilled winter oats and winter rye into it.

Yield difference He said: I think were going to get a harvest, but the yield difference is absolutely critical.

If we go in and its half the yield, then it doesnt matter how excited weve been about the clover establishment.

Arable and sheep farmer Jamie Stephens, who has been experimenting with living mulches for a few years, said for those that do not want sheep, choosing a micro clover that will not grow too big could be an option.

However, I dont know what the root structure would be like underground with a smaller leaf, he added.

His clover failed to establish last spring due to drought and he is in the process of trying again with a mix that includes a higher proportion of medium leaf clovers that he hopes will aid grazing.

Mr Stephens has also adapted a CTM Weedsurfer to inter-row in the living mulch.

He plans to undersow spring oats with the living mulch, using the oats as a nursery crop for the mulch.

The principle of it is all absolutely doable, and the potential of this working is massive on all levels for farm efficiency, less burning of fossil fuels, wildlife and having permanent ground cover, he said.

We could grow more crops because there wouldnt be any dead space in the cropping cycle farm productivity could rise massively.

Mr Alexander plans to keep the trials going for three years to assess the state of the soils at the end of it, including P+K content and organic matter.

The growers in the group have used establishment methods ranging from plough ing versus direct drilling, disc drills and tine drills, as well as different seed rates.

The Field Lab will be benchmarking the costs of using a living mulch strategy, for both organic and conventional no-till systems.

A living mulch system includes aspects of several common farming practices and concepts, such as cover cropping, intercropping, undersowing and mulching, with the system building upon these approaches with full integration as a cropping system.

In practical terms, it requires the establishment of a perennial forage legume to provide protection for the soil as a (semi-)permanent ground cover common to perennial cropping systems, such as top fruit or viticulture.

It is rarely used in annual cropping systems due to the competition with the cash crop.