Focusing on soil structure to retain healthy grasslands
When to use aerators and sward lifters
A recent Defra-funded study of 300 grassland fields found that just 40 per cent had good soil structure. That alarming figure serves to reinforce the importance of an ongoing initiative from AHDB’s beef, lamb and dairy sectors – Healthy Grassland Soils – which aims to help grassland farmers study soil properties and choose the best management practices.
At this time of year, farmers should be investigating the health status of grassland soils, as where action needs to be taken this can be done straight away. At the end of the summer, soils are less dry and it’s a good time to assess their structure. Using aerators or sward lifters in the autumn also means that the soil and the roots have the winter to recover before the high demands of spring when grass growth really gets going.
In cases of mild compaction, soils do have a capacity to recover on their own, especially if the cause, such as grazing livestock, is be removed. In these situations it may be worth monitoring the field over a few weeks to see whether it improves. Taking photos on a phone is a simple but useful way to track soil condition.
AHDB has produced a scoring system for grassland soils which helps to identify fields that need monitoring and ones that need action. If soils score four or five on the scale then action is required with an aerator or sward lifter.
There is good evidence that using aerators or sward lifters in soils without poor structure has limited benefit and can cause damage, especially if the soil conditions are not appropriate.
If an aerator or sward lifter needs to be used, it is important to make sure soil moisture conditions are correct to avoid further damage. If a handful of soil obtained from the depth that needs to be worked gives a moist smooth surface when rolled then it is too wet to work. If the soil starts to crack then the soil conditions are appropriate.
Aerators and sward lifters need to be working 2.5cm below the problem area so dig holes to make sure the equipment is doing the correct job.
As part of the Healthy Grassland Soils project, soil structure assessment tools and a website — www.healthygrasslandsoils.co.uk — have been developed with more technical information, especially in relation to soil biology. An assessment sheet and pocketbook is available from the AHDB Beef & Lamb Better Returns Programme.