Subsoiling could help stock farmers deal with drainage and drought

Experience of the benefits of grassland subsoiling on a St Columb dairy unit over the past year suggests the practice could help this spring in repairing and rejuvenating soils that have been sodden for much of the winter, not only by immediately improving drainage, but also in the longer term by aiding grass root development.

Cornwall Farm Machinery – based at Crowlas, Penzance – which holds the county’s franchise for Sumo drills and cultivation equipment, has now supplied a number of GLS grassland subsoilers to the area’s livestock farms, with interest growing in the drainage, aeration and root development benefits of loosening through the soil profile as opposed to simply slitting, spiking or scarifying.

One of the county’s farms where a significant difference in grass quality and quantity has been noted since grassland subsoiling was first undertaken is FG Brewer and Son Ltd’s unit at Fraddon, near St Columb.

Andrew Brewer, who milks 650 Holstein/Jersey crosses, purchased a Sumo GLS from CFM last spring. Having subsoiled a significant part of his grassland – mostly permanent pasture with a few short-term leys – he reports some pleasing results despite the challenging weather of the past year.

“We have a range of soils, some heavier than others, but we graze all year round, and at a high stocking rate, with milkers at four cows/ha,” Mr Brewer explains.

“That’s done to keep grass covers tightly-grazed for good regrowth, but it does mean a high density of hooves on a relatively small area. Coupled with the weight of forage harvesting machinery when silage making is taking place, we need to make sure we’re managing compaction.”

That need became a particularly prominent problem after the wet summer of 2012, when the high rainfall exacerbated the issue. With his cows being his core focus, and machinery regarded as a necessary cost, Mr Brewer was keen to invest only in equipment that could be relied on to alleviate compaction effectively but with minimal complexity.

“We borrowed one machine from a neighbour, but I felt it wasn’t doing enough in terms of lifting the ground to get air into it, sort the compaction, and improve the drainage.

“I then demoed a Sumo GLS from Cornwall Farm Machinery. What particularly impressed me about that, and made me decide to buy one, was the lift it gave to the soil through the full working depth, and the finish it left, with minimal surface disturbance.”

Since purchasing his GLS last spring, Mr Brewer has now subsoiled 80% of his grazing land, and the results have been notable, despite the less than ideal conditions in which some work had to take place.

“It does its best work when the soil is drier and cracks more fully, in spring and early summer, when the grass is ready for a peak growth phase and is actively growing beneath the surface as well as above it.”

The principle is that the roots are then better able to seek out the spaces created by the soil fracturing, he suggests.

“Given the tough spring we had, the results last summer were good, with digs showing an improved root mass at the full 9in loosening depth.

“As well as improving drainage through the spring and helping the roots seek out more water during the summer, that was also clearly translating into improved access to nutrients. We use a rising plate meter to measure weekly grass growth, and last spring were recording 20kg/day more drymatter cover per hectare on land that had been subsoiled with the GLS,” adds Mr Brewer.

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