As featured in Arable Farming Magazine
Tools to take cover with
by Arable Farming August 2020
The benefits of cover crops are being explored by many growers, but careful management is needed to ensure residues do not hamper the following crop. Jane Carley gets guidance on destruction principles and looks at tools for the job.
Management of cover crop residues often depends on the drill to hand and the drilling philosophy for the following crop, says agronomist David Felce, whose work for Agrii includes cover crop trials on heavy land at Stow Longa in Cambridgeshire.
“Do you need to move soil and create a tilth, or are you aiming at low disturbance, and is it a disc or tine drill? Drills which move less soil may need help from a cultivation tool,” he says.
Where the cover crop is destroyed by spraying, timing ahead of drilling becomes significant, says Mr Felce.
“Generally, six weeks is needed before establishing the next crop. The results are better if the cover crop is comprehensively removed as it can use moisture needed for the cash crop or create a shading effect if left for too long, which can prevent the soil surface from drying out to create a friable drilling surface in spring.”
Trials have shown a visible difference between springdrilled plots where cover crops were removed earlier and those drilled ‘on the green’.
“Cover crops established in late August should be sprayed off at Christmas, as they will have achieved their purpose by then; those with a good rooting system will continue to offer benefits even when the top is killed off,” says Mr Felce.
“We have found that where the purpose is restructuring, the best results are achieved by a combination of ‘roots and metal’.”
The requirement to work into cover crop residues has become more significant as bigger mixes are used to get the rooting effects – these are more difficult
to kill off than mustard or buckwheat and can return as volunteers.
In order to chop residues or green material without excessive soil movement, a disc must offer a vertical chopping action rather than sliding across the surface,
says Mr Felce.
“Disc drills offer lower disturbance, but can lead to hairpinning and poor establishment in heavy residues.”
For drills with sufficient coulter pressure to cut through trash, such as a John Deere 750A or Sky drill, a crimping tool may be sufficient, either on the front
of the drill itself or front linkage of the drilling tractor.
“This could work where there is a good cover crop canopy, it hasn’t been sprayed off or was sprayed off late and is still anchored in the soil. The tool simply lays the crop down to allow the drill to cut the seed in.”
Tine drills can also work into crimped cover, although the long material can cause them to block up, so good tine stagger and spacing is needed, Mr Felce says.
When working into green cover which will be retained, a grass rejuvenation type drill such as the Cross Slot or T-Sem can work well, ‘stitching’ the seed into friable soil below the cover.
“You can also use a disc drill with good coulter pressure, but those with cultivation elements are not ideal as they will destroy too much of the sward.”