Shelving a tried-and-tested drilling set-up on a 1,600ha arable farm that regularly returns healthy yields is a brave move.

But Hampshire farm manager David Miller reckons switching to zero till is the only way to improve his soil health and help drive yields beyond their current level.

See also: Cross Slot drill planting cover crops in our Harvest 2015 film

This year he invested in a £190,000 Cross Slot drill from New Zealand and has been busy using it to establish a series of different cover crops and cereals.

We caught up with him earlier this autumn to see how he was getting on with it.

Why the switch to zero till?

For years we had been using a fairly standard min-till system with a Simba SL doing most of the cultivation work and a Vaderstad Rapid and Horsch Sprinter doing the planting. 

We were getting good yields, but had definitely hit a plateau, which I was convinced was down to the condition of our soils.

Our organic matter levels are between 5% and 6%, which isn’t too bad, but I wanted to get them higher.

I started to look into growing cover crops to increase organic matter and improve soil structure.

After that I quickly got into the idea of zero-till drilling and the more I looked into it the more in made sense.

Why the Cross Slot?

I looked at several drills, but the Cross Slot was the only one that ticked all the boxes.

It is incredibly solid, comes with seed and fertiliser hoppers and the T-shaped opener gives very accurate placement of both seed and fertiliser.

The price seemed high at first, but it’s the only piece of planting equipment we need and the sale of all the other equipment helped take the edge off the bill.

How did you get the drill into the country?

We bought the drill through Paul and James Alexander who run a company called Primewest. 

They build their own drills at their Oxfordshire farm using the Cross Slot openers, but also import the original drills from New Zealand, which are built by Baker No-Tillage.

In the end we decided to go for a 6m New Zealand-built version as it had twin seed and fertiliser hoppers.

What other cultivation kit have you got left?

We sold everything other than a set of Cambridge rolls and the subsoiler – just in case we need to help lift the soil in the first few years.

How does the Cross Slot system work?

Each drilling assembly has a disc opener with an L-shaped coulter on each side – one for seed and one for fertiliser.

As these slice through the soil profile they create an inverted T-shaped slot in the soil with a seed placed on one side and fertiliser on the other.

When the seed and fertiliser has been placed, a set of double presswheels close up the slot.

Then, as the seed germinates, it picks up the fertiliser and grows through the channel cut by the disc opener.

We’ve been planting catch and cover crops directly into standing straw left behind by our stripper header and chopped straw.

Cereals have then been planted into the remains of the cover or catch crop that’s been sprayed off with glyphosate.

How has is performed?

So far we’ve planted 1,000ha of catch crops and cover crops (see “Experimenting with cover crops”, below), 600ha of cereals and the drill has performed well.

We’re still learning, though, and there have been a couple of teething problems. Firstly, in light, fluffy soils we found that the presswheels would start to bulldoze the soil and create a bit of a bow wave.

As well as moving the soil – which we don’t want – this would also cause the presswheels to block.

To help get around the problem we put less pressure on the presswheels and drilled at an angle to the previous year’s crop.

But because we were putting a bit less pressure on the presswheels we were also finding the slot wasn’t closing up fully. We managed to close it up with a quick pass of the Cambridge rolls, though.

As our organic matter builds up and we get more roots holding the soil together I see this being less of a problem.

In terms of establishment, most of the cover and catch crops went in well and generated a large amount of biomass very quickly.

We did have a couple of failed establishments, but that was more due to the poor conditions in September than the drill itself. The cereals seem to be going in well so far.

Is it difficult to pull?

We’re pulling the drill with a 360hp Fendt 936 and it has just enough power to plant at 10kph.

We’ve also had to ballast it pretty heavily and drop the tyre pressures right down to get enough grip. As the soil improves I’m hoping it the drill will get easier to pull.

How much does it cost to establish a crop?

For diesel and wearing parts it costs about £8/ha, which is £4/ha less than it cost to run our old Simba SL – if you work the fuel cost out across over the whole year, we’re saving about 20p/ha at current prices.

However, we’re spending £40/ha for cover crop seed and £30/ha catch crop seed. We’re not doing this to save money – its about improving the long-term health of our soils and increasing yields.

Are you expecting yields to drop next harvest?

In the short term there’s a chance yields might drop before they start to climb.

However, it’s no good judging the system after year one – you need to look at it over at least five years.

We’ve worked out that we can take a yield drop of 0.35t/ha before we’re worse off than we were with the old system.

What’s next?

We’ll continue to experiment with different cover crops and rotations to see what works best and I’m hoping to be able to grow winter cereal crops back to back (see below).

We’re also going to be putting in an RTK guidance mast as the Egnos system we are using at the moment just isn’t accurate enough or reliable enough for drilling.

Experimenting with cover crops

Planting fast-growing cover and catch crops is an integral part of Mr Miller’s strategy to improve soil health and improve yields.

Catch crops are grown in the sort window between harvest and establishing an autumn-sown crop.

The varieties in this custom mix are picked for their ability to quickly build root mass and green vegetation, fix nitrogen and hopefully reduce the risk of take-all.

The plan is that he’ll successfully be able to grow back-to-back cereals, using the catch crop as the only break.

Mr Miller says catch crops planted in the first half of August 2015 romped away and built up an impressive amount of organic matter, but those planted in the second half of the month struggled.

The cover crop mixes he is establishing are designed to be in the ground for about six months and he is playing around with several different seed blends.

Some of these are EFA-compliant mixes, but the most successful ones he has planted so far have been those he has designed with his seed merchant. These include crops like tillage radish, oil radish, vetch and phacelia.

Before planting the following cereal or oilseed crop the cover and catch crops are burnt off with glyphosate and the drill plants directly into it.