Building Healthier Soils Within an Intensive Rotation
A Shropshire estate is determined to show soil health can be improved within an intensive root-cropping rotation as it strives to bolster its environmental and financial sustainability.
The 350ha Isle Estate on the banks of the River Severn northwest of Shrewsbury has been owned by the same family since the reign of Queen Elizabeth I and its current lifetime tenant and trustee Edward Tate is eager to secure a sustainable future for the farm.
“As a business, it has to be productive and profitable, but we’ve also got a duty to hand the land back in better condition than we took on,” he says.
“Soil is our main asset and we must nurture it for current use and future generations.”
However, Mr Tate acknowledges growing potatoes in the rotation, although profitable, is not usually conducive to building healthier soil given the mechanical disturbance involved.
He worries that recent years have seen arable yields plateau, possibly because of organic matter depletion, declining soil biodiversity and compaction issues. There is the added challenge of preventing nutrients leaching into the river that almost surrounds the farm.
As part of the drive to tackle these problems, Hutchinsons agronomist Ed Brown has been called upon to conduct a thorough assessment of the current soil conditions and develop a long-term management plan.
The estate has also teamed up with experts from Harper Adams and Ashton Universities, and The Field Studies Council for a five year project to enhance the natural environment and biodiversity.
Benchmarking current status
The starting point for any soil management plan is to accurately assess the existing status.
“Quantification and knowing where you’re starting from is crucial,” says Mr Tate.
Two years ago an electromagnetic survey was carried out to map variations in soil type across the arable area. Mr Brown “sense-checked” readings in the field to ensure the soil texture map was accurate and EM reading variations were due to genuine textural differences, not other factors, such as compaction.
A Healthy Soils assessment was then carried out on three fields of different soil types. This shows:
Three main soil types: sandy silt loam, sandy loam and clay loam
- Soil type and bulk density readings confirm soil is sensitive to overworking. Slumping, compaction and poor infiltration are particular issues
- Biodiversity assessments show a large decline in worm numbers after potatoes compared with fields that have been out of potatoes for five years (highest population in wheat land)
- Good phosphate and potash reserves in two of three fields assessed – low areas prioritised to receive compost
- Reasonable organic matter content (c.3.5%), but need to replace seasonal carbon losses and increase overall level.
“We’re certainly not starting from rock bottom as there were a lot of positives, but there are many things we can improve,” Mr Brown says.
“Hopefully this farm will demonstrate improvements to soil health can be made while still growing a productive rotation that includes intensive crops like potatoes. It’s not always about drastic changes to rotation and switching to direct drilling.”
Having identified the main areas to target, various measures are being employed to improve the overall health and resilience of soils.
The inspiration for trying cover crops came after seeing the benefits of leaving wheat volunteers to grow over winter ahead of spring cropping, says Mr Brown.
Roots stabilise the soil to prevent slumping (*see picture), break compacted layers, improve natural drainage and the ability to travel in spring.
Cover crops also help dry soil to depth, aid natural structuring, conserve surface moisture and return useful organic matter (c.0.02% a year) and nutrients, he says.
“I’d always been keen on the idea, now we’ve implemented extensive use of cover crops across the farm,” Mr Tate adds. “I call it green ploughing.”
Two types have been established using an Amazone AD-P 3000 Special mounted on an Amazone KX 3000 power harrow straight into wheat stubble. One is a straight 50kg/ha of oats, the other is a mix of vetch, oilseeds and oats.
“Cover crops affect the soil’s moisture profile, so we’ll wait to see how the weather goes over winter before deciding when to spray them off,” notes Mr Brown.
Jonathan Birchall, director of agribusiness at Carter Jonas acknowledges more work is needed to get the best from cover crops in the rotation, but suggests there may be scope to use them as a natural biofumigant ahead of potatoes to help control pests such as potato cyst nematode.
Applications of green waste compost from Shrewsbury Council are an important source of nutrition (nitrogen, phosphate and potash) and organic matter across the farm.
Based on findings from the Healthy Soils tests, organic matter levels average around 3.5% in many fields, and while this is reasonably good, there is scope to increase this while replacing seasonal losses, says Mr Brown.
Mr Birchall plans a split-field trial exploring the benefits of compost application rates in more detail. After this harvest, the field (currently in wheat) will be split into equal thirds, with one part receiving a standard dose onto stubble at each timing, another will get a double dose, while no compost will go onto the final third.
A range of assessments will be taken to measure the effects on crop growth (tissue analysis, tiller counts, etc), soil health and biodiversity, he says.
Variable rate nitrogen applications are also being considered for future, although Mr Birchall says this depends on the contractor having the necessary equipment.
A conventional plough-based cultivation system is traditionally used on the estate, especially fields going into potatoes and maize. However, the aim is to be more flexible with cultivations, and minimal tillage (Heva Combi-Disc) has been used for the first time in 2018 to establish wheat.
“We contract-out all mechanical work, which has previously meant accepting a one-size-fits-all approach. However, we had opportunity to change contractors two years ago and now Gethin & Co fully support and are key to what we’re trying to achieve, which is crucial,” Mr Tate says.
While true direct drilling may not be suitable, Mr Brown says one-pass systems and shallow cultivations are feasible in parts of the rotation and will aid natural structuring.
Integration of environmental stewardship options is further helping manage soil issues at the Isle Estate.
Land most prone to flooding has been switched from arable production into grass or higher level stewardship, while 6-12m pollen & nectar mixes have been established alongside other parts of the river to stabilise soil and minimise risk of soil/nutrient runoff.
Mr Birchall says they are also exploring whether stewardship options can be employed on field headlands to allow machines to turn on un-cropped areas. “It’s easy to see the effect of headland turning on yields, so if we can avoid this problem it will improve overall field margins.”
*Find out how a Healthy Soils assessment and report can benefit your business at www.healthysoils.co.uk or call 01526 831000.
Farming at the Isle Estate
- 130ha (320 acres) cultivated
- Generally sandy loam soil
- Seasonal grazing for 600 sheep and woodland
- Cropping includes milling wheat, fodder maize and potatoes for Walkers crisps.
Route to healthier soil
- Thoroughly assess soil health to highlight problem areas
- Plan management carefully and monitor progress
- Ensure everybody is on-board with the objectives
- Be flexible with cultivations
- Maximise use of cover crops
- Apply green waste compost for organic matter and nutrients
- Integrate environmental and stewardship options to help address soil issues.