In recent years, a number of commercially made interrow drills have come to the market, however, one Yorkshire farmer has been using a homemade version for the past five years. Alex Heath finds out more.
Having seen interrow sowing being carried out in Germany, Oliver Mackintosh of WJ an LA Mackintosh says he could see the merits of the practice and decided to build his own interrow sowing machine.
That was back in 2015 and formed part of his final year dissertation at Harper Adams University, which focused on soil health and erosion.
The business farms near Doncaster, Yorkshire, with a waste recycling site, arable cropping and harvesting maize for an on-farm AD unit, which can be eventful, says Mr Mackintosh, with plenty of saturated peat fields to contend with come October. This year the company harvested 1,400ha of maize.
To combat the challenges involved in harvesting maize and provide structure to the wet ground, Mr Mackintosh set about building his own machine, as there were not any on the market in the UK at the time.
He explains; “The model currently used on the farm is the second design. I wanted to prove the idea would work in the first instance so made it on the cheap with parts scavenged from around the yard and picked up in second hand sales.”
Capable of drilling eight rows, the first design was constructed using an old Stanhay beet drill frame and Suffolk coulters. These were sourced from a drill that had gone unsold through Cheffins’ monthly machinery sale, but snapped up after the event by Mr Mackintosh. With the drill cannibalised and the interrow machine built and ready to roll, the first undersown grass crop was planted in June 2015.
“The idea worked and we had grass growing in the rows between the maize,” says Mr Mackintosh. “However, it was by no means perfect. The Suffolk coulters would not penetrate hard soils and in the wheeling behind the tractor it just placed the seed on top. This led to uneven emergence and as there was no consolidation behind the coulter, some was just planted into air pockets and did not emerge.
“That harvest, the areas that had been planted and emerged well, travelled better, giving me enough confidence to have a rethink and redesign the drill.”
A second frame, the same as before was sourced, but a different coulter was chosen. Disc coulters from Weaving now feature on the current model - a much better choice, according to Mr Mackintosh. With a double disc opener, Mr Mackintosh says seed is placed at a more even depth and is covered with a sprinkling of soil that falls back into the void cut by the discs. At the rear of the coulter units is a rubber wheel which firms the seeding slot.
“The frame has a small amount of oscillation on each of the hydraulically folding wings, pivoting in the middle, giving a limited amount of contour following. The coulter units are protected from hard objects with a spring,” he says.
To carry and distribute the grass seed to the 16 coulters, a Stocks TurboJet seeder with eight outlets is used. Each row has two coulters fitted, 250mm apart, leaving the same distance between all the plants that have been planted. The pipe from the seeder has a Y piece fitted, allowing the seed to be split evenly between the coulters.
“The seeder came off an old rape drill that was no longer used. Along with the new coulters, we used new pipework and fittings throughout. A bit of hot water and the 50mm pipe easily slipped into the coulter units,” he adds.
Rate control is governed with a GPS speed sensor on top of the tractor cab. Tractor of choice for this task is a Ford 5610, says Mr Mackintosh. Fitted with an original set of tyres, the same width as modern row crops, he says the old tractor has just enough lifting capacity to hoist the drill out of the ground and pulls it well, right up to its seventh gear when it runs out of steam. However, the tractor itself does not have GPS steering, requiring the operator to manually steer down the rows, which is an easy enough task, given the maize is planted with GPS, says Mr Mackintosh.
Grass is sown at 8kg/ha with work rates of up to 40ha per day achievable, reports Mr Mackintosh. “We tend to let the maize get away, then when it is around knee height at the six to eight leaf stage, we will sow the grass. This is a good time as the plants are well established and still short enough to get under the seeding bar. The seed needs to go into moisture and loose soil. The press wheel on the back of the coulter does enough consolidation so that the seed sits in a seam of moisture,” says Mr Mackintosh.
However, the whole of the farm’s maize area is not under sown with grass. Instead, a policy of targeting the farm’s problem fields is implemented, with the aim of improving the soil structure and ability to travel. He says this year 200ha was undersown. This included fields that suffer from flooding and lie wet at harvest, he says.
“There is a noticeable difference when driving on the fields that have been undersown, with trailer tyres staying cleaner and making less of a depression, thanks to the mat of roots from the grass plants. The ground feels firmer and there is definitely less movement in the soil. We have not had any major mishaps with trailers getting stuck this year, so it certainly makes a difference to the weight the ground can carry.
“The grass also stops water sheeting off the fields in periods of heavy rainfall and acts like a filter for soil as water travels to the ditches,” adds Mr Mackintosh.
Once the maize has been harvested, the grass is left over winter, with some fields grazed by sheep. “The grass is incorporated ahead of planting, providing valuable nutrients to the growing maize plants the following year,” he says.
In addition, the farm direct drills wholecrop mixes into the grass and maize stubble and this year has experimented with rolling the growing grass plants after the maize has been removed. The idea behind the process is it gives the grass a growth kick, as well as flattening and snapping off more of the maize stalks, which should encourage them to rot down quicker and be less of an issue when harvesting the wholecrop.
Overall, the homemade interrow drill is a valuable addition to Mackintosh Maize’s fleet and is proving to be a cost effective tool for improving the land farmed, with nutritional, environmental and logistical benefits, says Mr Mackintosh.