Precision approach to reviewing soils and nutrition is a win-win – British Dairying

With 950 dairy cows and 750ha of cropping, Martin Dairy is a large enterprise that recognises the importance of being as resilient as possible to the environmental and financial pressures facing the sector.

The farm grows a range of crops, including forage maize, winter wheat for crimping, winter and spring barley, forage rye and grass on predominantly silty clay loam soils, much of which is rented from local landowners.

Richard Martin, who heads the arable operation, believes soil health is at the heart of improving resilience. He is working with Hutchinsons agronomist, James Whatty, to make some significant changes, based on a more detailed understanding of soils gained through in-depth soil testing and the latest digital scanning technology.

Traditionally, the business has operated a plough-based establishment system, but Richard knows this can present challenges in some seasons, and believes reducing tillage intensity is key to improving the soil’s resilience to more extreme weather.

During autumn 2022 with that in mind, he hosted a direct drilling demonstration on a field coming out of maize going into winter barley. Before the demonstration, a Healthy Soils Gold test was conducted on the land to understand the soil characteristics better and the most appropriate management techniques.

Testing confirmed that soils were generally in good condition, with high organic matter content at 7-12%, and high fertility, given the use of organic manures and slurry over many years. The buffer pH was also relatively high at 7-7.5, indicating soils will naturally revert to a higher ‘resting’ pH.

The carbon:nitrogen ratio was very low though, at 7.5:1, when the optimum is 24:1.”With large quantities of organic manures applied through the rotation, this low ratio means nitrogen can be rapidly released from the soil through mineralisation, potentially meaning we are not fully utilising the nitrogen within the system” explains James.

This is something they are looking to manage with more tailored cover crop mixes.

Although the farm has not converted to a full direct drilling system, non-inversion tillage is now used for establishing cereals, based around a Sumo Trio and a 3m Pottinger combination drill. “We haven’t ploughed anything for autumn cereals for two years now,” says Richard. “It’s been a big change, but considering how wet it has been over the [2023/24] winter, our fields travelled reasonably well this spring because they haven’t been ploughed.

“I’m not saying it’s perfect; there are still problems to overcome, but it’s definitely quicker, is saving us a bit of money on establishment, and I feel is doing a better job by letting the soil do some of the work for us.”

Flexibility is key though, and land going into maize is still ploughed, Richard notes. “We find ploughing is a good way of aerating the soil and creating a nice seedbed for maize to go into, and helps us to incorporate organic matter.

“Saying that, we’re keen to try new approaches. We’ve trialled a Horizon strip-till drill for maize, but the kit is very specialist, and last year we tried drilling some maize with the cereal drill which worked okay, but still wasn’t as effective as the specialist maize drill. Ideally we’d like one machine capable of doing everything.” As part of the focus on soils, Richard is also digitally mapping soils across the farm using Terramap high definition scanning, which provides a comprehensive picture of all common soil properties in far greater detail than conventional grid sampling, mapping 800 data reference points per hectare.

So far, around 65ha has been Terramapped, and he hopes to have the whole arable area scanned on a rolling basis over the next five years, with results uploaded to Omnia for analysis. “Terramapping has already opened my eyes to the variations in some fields” says Richard. “The first fields we mapped were on sloping land deliberately chosen because it was likely to be more variable, but even so, some results were still a surprise. Phosphate and potash, for example, showed particular variation, with higher levels at the top of the slope than further down, which was the reverse of what I expected.”

Mapping in-field variability has opened the door to variable input applications, principally fertiliser, but he also plans to try variable seed rates on cereals this coming autumn. “The cost of soil testing is soon paid for by the savings you make applying fertiliser where it is needed, and it’s the right thing to do environmentally.” They have also started using micro-nutrition starter fertilisers in maize (Primary-P), to reduce reliance on diammonium phosphate (DAP), which has historically been applied at a flat rate on the drill. Variable rate starter fertilisers are a future possibility, although this will require investment in a new drill, so Richard wants to be confident in the approach before making such a move. Last season, they also tried reducing DAP rates on one block of land with high P indices, with no starter fertiliser, and maize performed well with no obvious yield differences to the standard DAP approach.

Elsewhere, variable rate nitrogen is being tried for the first time this spring on an 18ha block of winter barley. Rates were varied according to normalised difference vegetation index (NDVI) imagery available through Omnia, with more nitrogen applied to boost lower biomass areas, and less to denser parts. From a baseline of 85kg N/ha, rates varied by +/-15-20kg N/ha, James notes. “It’ll be interesting to see how that evens the crop up and whether there is any impact on yield.”

Last season, they also trialled a foliar bacterial nitrogen-fixing product to see if it could help better utilise high levels of soil nitrogen. James says results were encouraging, with a 1t/ha yield response, so it is something they plan to try again this season.

Cover crops are an important part of the rotation, with 40-60ha in the ground most seasons, usually to protect soils over the winter, between winter barley harvest and sowing maize the following spring.

Richard has previously favoured forage rape for this, grazing it overwinter with either cattle or sheep. “However, in wet winters, cattle can cause some damage to the soil, so we want to explore alternative mixes that are more tailored to what the soil needs, but can still be grazed by sheep.”

The farm has recently purchased a second-hand 6m Vaderstad Rapid drill, primarily for sowing cover crops behind winter barley. But Richard also plans to use it to over-sow legume and herb seeds into existing grass leys as part of the sustainable farming incentive herbal leys option (SAM3).