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11 Aug 2021

Cover crop benefits beyond nematode control

As featured in Arable Farming Magazine

Cover crop benefits beyond nematode control

by Arable Farming

Nottinghamshire grower Will Baker started planting cover crops while looking for alternatives to nematicides, but realised the benefits extend much further than just nematode control.

Will Baker heads up Thoresby Farming, a 2,500- hectare arable enterprise in Nottinghamshire which grows combinable crops, beans, root vegetables, sugar beet and maize.

He says: Nematodes have historically been problematic in our soils and with limited chemical options available, we looked into alternative options for controlling them.

As a result, we teamed up with Kings and Severn Trent to see how cover crops could work and set up a trial in one of our fields.

With advice and support from Kings on the best cover crop mix to plant and through a Severn Trent Environmental Protection Scheme (Steps) grant, the business was able to secure £60/ha to establish the crop.

In previous years, weve also used this grant to undersow our maize and to install a biobed to help protect watercourses in our area, adds Mr Baker.

Investments The latest Steps grant has been hugely beneficial, as its allowed us to make investments that we wouldnt have made, which have had significant environmental and performance benefits.

Jim Egan, Kings technical adviser, says the primary focus for Thoresby Farming was to reduce nematode populations.

The first job was to undertake a free-living nematode sample.

The results showed that root lesion nematode populations were particularly high.

We then designed the cover crop mix with this in mind, as well as considering how to minimise wind blow and enhance soil structure, due to parts of the farm having very sandy soils.

The mix was simple, a combination of Defender oil radish and black oats, which was planted in September 2020.

What made the trial different was that Mr Baker wanted to understand if the cultivation technique impacted the success of the cover crop.

So, we trialled four techniques and split the field into quarters.

The four cultivation methods included using a strip-till drill, subsoiling and then drilling with a Vaderstad Rapid, the Vaderstad Rapid drill alone and a Claydon drill.

We then set up Soyl mapping on the field which highlighted distinct variations between the different establishment techniques.

In November 2020, we took a fresh weight cut, to see how much nutrient had been taken up by the cover crop.

The crops from the plots that used the strip drill and Vader stad drill alone had 40kg/N/ha, the Claydon plot had 67kg/N/ ha, the subsoiled plot had 75kg/N/ha.

The potassium and potash levels were also higher than the other plots.

The cover crops allowed the nitrogen, phosphorus and potassium to be stored by the cover crop, helping reduce eaching and nutrient loss over winter.

We believe the reason there was higher nutrient uptake in the subsoiled plot was because heavier cultivation can help with the release of microbes in the soil, helping to breakdown the soil structure to release nutrients.

Nematode populations were checked again in April and the cover was then destroyed for the following maize crop.

Ongoing monitoring indicated a reduction of more than 99% in the target nematodes between July 2020 and April 2021.

This was attributed to the careful selection of the cover crop mix and the use of multi-resistant radish.

Mr Egan adds that it is, however, important to note that different cover crop species can have different impacts on nematodes, so it is important to identify which nematode species is present first.

Prior to planting the cover crop in this specific trial there was winter wheat on the field and a section of crop didnt grow, but due to its location it still received the same level of fertiliser as the good crop.

Rooting When tested, the cover crop in this smaller area contained 202kg/N/ha, 190kg/K/ha and 25kg/P/ha, which is considerably higher than the rest of the field, he says.

While at first glance the cover grown on the previously uncropped area looked consider ably better, there was no difference in rooting, which meant all the soil nutrients had gone into growing the crop rather than excessive root growth to find nutrients in the soil.

Thoresby Farming has seen fantastic results to date, with a significant reduction in nematode populations, reduced nutrient leaching and soil erosion, with more nitrogen available in the soil, allowing the crops to perform better and with fewer inputs required.

Our next step is to develop a better understanding of the point at which the following crop starts to take up nutrients in the soil as this will show the true benefits in terms of nutrient storage and utilisation.

The important thing to remember here is this is a win-win situation, as it provides financial and performance benefits for the grower, while also improving water quality, he adds.

Funding options

Severn Trent is offering increased funding to Midland farmers in ground water catchments to encourage the planting of cover crops, to improve soil structure and protect water quality.

Jodie Rettino, catchment management and biodiversity business lead at Severn Trent, says the water company has already supported more than 5,000 farmers through its Farming for Water programme.

Were looking to work closely with growers wanting to improve soil health to help overcome the environmental and economic challenge of nitrate run-off and leaching.

There have been several barriers affecting the uptake of cover crop planting, such as concerns around the cover acting as a host for pests and disease over winter, often known as the ‘green bridge, establishment costs and the struggle to see a return on investment.

However, Severn Trents agricultural advisers offer financial and consultative support on establishing the crop for growers to realise both economic and environmental benefits, says Dr Rettino.

Steps is open until January 31, 2022.

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