Act now to remove soil compaction in grassland and gain next spring from an earlier turnout and increased grass production. That’s the advice from agronomist Ian Robertson, of Sustainable Soil Management.
“The deeper soil compaction caused by heavy machinery can reduce grass dry matter yields by up to 25%. This problem requires subsoiling or sward-lifting to restore soil structure,” explains Mr Robertson.
“The autumn months are the ideal time to sward-lift ground. This produces a ‘shatter’ that, in turn, creates fissures through the soil profile and allows the movement of air and water.”
While soil temperatures are above 10°C, this stimulates microbial activity and fixes nitrogen and mobilises phosphate. These are key for plant growth, and this extra nutrient supply encourages the growth of new roots into the gaps created by the shatter.
“Another benefit of autumn subsoiling is that winter rain can then flush iron particles in the soil profile away from plant roots. Iron is an antagonist that locks up phosphate and manganese and, ultimately, can reduce levels of these key nutrients in grass and forage, impacting on animal performance,” says Mr Robertson.
“Removing compaction in advance of the winter will also prevent waterlogging and the consequent plant root death. In the spring, fields will dry out and warm up sooner.
“Don’t leave it too late though,” he warns. “There’s no point aerating soil if it’s not warm enough for the plant to be actively growing. And don’t sward-lift if the ground is wet and elastic because then it just absorbs the energy and ‘smears’. The profile needs to be dry enough to shatter.”