“Clever cultivation can mean anything from not cultivating at all to subsoiling or ploughing where necessary,” says Ian Robertson, head of soil health at Hutchinsons. “As a general rule, never cultivate at the same depth every year and make sure whatever you do delivers what the soil actually needs.”
Recent seasons have highlighted the need to make soils more resilient to wet and dry conditions. In the rush to prepare ground for drilling it can be all too easy to go straight in with the cultivator or subsoiler as soon as the combine leaves the field, but that may not be best for soil health or crop establishment.
“Before doing anything, it is important to stop, take a step back and consider what the soil actually needs,” says Ian Robertson, who urges growers to adopt a flexible “clever cultivation” strategy.
Mr Robertson notes the rising popularity of low disturbance subsoilers for rectifying structural issues in shallow tillage systems. Such implements are often needed to break up distinct layers that can form where ground has been repeatedly cultivated at a shallow depth (typically 50 mm), potentially restricting water infiltration and root growth.
In many cases, the need for this remedial action could have been avoided by adopting a more varied approach to cultivations, he says.
Understand soil requirements – 3 step strategy
Step 1 – Dig a few holes. Identify whether there are any structural issues that needed addressing, such as compaction or poor drainage.
Step 2 – Use bubble test to see if soils are compacted. It is best to make soil assessments in spring or autumn when ground is moist and warm, with active root growth and biological activity. When assessing soils in summer care is needed not to mistake dry, hard soil for being compacted. The bubble test is a simple way of identifying whether dry soils are compacted. Infiltration tests are also useful, but when conducted in summer, make sure water does not flow straight down cracks.
Mr Robinson says: “Typically, 50% of soil is made up of air and water, so it may be that rock hard ground just needs wetting-up again to return to a friable surface that can be drilled straight into.
“In the past two years we’ve seen examples where growers have rushed to create a seedbed after harvest, only for heavy rain to make it unworkable and un-drillable later in autumn. In some cases it may have been better not to touch it.”
Step 3 – Leave root networks undisturbed. Root networks left by crops, even low yielding ones, do a fantastic job of stabilising soil aggregates, improving porosity and structure of the top layer that crops are drilled into, so leaving this undisturbed can often be a better choice. Mr Robinson continues: “Nine times out of 10 the top 50 mm is actually in good condition.”
Clever cultivation to conserve moisture
Hutchinsons’ technical manager Dick Neale agrees: “Stubbles generally handle moisture much better than a cultivated surface. If you’ve got a nice friable surface that’s managed moisture well, most modern drills are capable of drilling directly into stubble, so there’s no need to cultivate. Cultivations destroy aggregate structure, which takes time to rebuild.”
Not disturbing the surface offers significant benefits for moisture conservation too, which can make all the difference when establishing crops such as oilseed rape or early-sown wheats in dry autumns, he adds. “Moisture conservation and managing moisture within the seedbed have got to be an absolute focus.”
Oilseed rape in particular is better direct-drilled with a disc or tine-based implement to minimise soil movement and conserve moisture, he says. Given the importance of achieving even sowing depth for such a small seed, he advises against seeder units on subsoilers and recommends growers plan rotations and cultivations carefully to ensure any structural issues are rectified in preceding seasons.