The first samples in Zone 2 of the Soil Nutrient Health Scheme (SNHS) were taken last week, with 190,000 fields across Fermanagh, south Tyrone and west Armagh to be assessed by the end of February 2024.
The £37m DAERA-funded scheme is being delivered by the Agri-Food and Biosciences Institute (AFBI) with soil samples collected by RPS Group.
In Zone 1, which mainly covers Co Down and the eastern side of Armagh, over 150,000 fields were sampled last winter. However, various issues, including the early application of slurry, mean around 8,000 to 9,000 fields are still outstanding.
Progress was also not helped by a wet December in 2022. Given prevailing soil types further west and current ground conditions, there are some concerns about the situation in Zone 2 – if fields are simply too wet to sample, they might have to be left until early spring.
Providing an update on the initial results from Zone 1 at the AFBI soil conference last Thursday, SNHS project lead Dr Rachel Cassidy said the general trends being seen are similar to that observed in work done across the Upper Bann catchment since 2016.
In Zone 1, a total of 58% of fields need lime. Where pH is below the optimal of 6.2 in mineral soils and 5.5 in peat soils, it means any nitrogen (N), phosphorus (P) or potassium (K) applied is less available for plant uptake.
Loss of P into waterways is a major contributing factor to lower water quality in NI and across Zone 1 farms, 45% are at Index 3 or above for P (the optimal index is 2+).
While there is a general surplus of P, Cassidy said there was huge variation in distribution across farms, especially in beef, where some P indexes were at zero while on intensive units, fields at Index 6 have been observed.
Dairy farms have the narrowest distribution, suggesting milk producers are actively engaged in managing their soils, said Cassidy. The average across the dairy farms in Zone 1 is just above the optimal.
“A modest change in management would take it to 2+,” she said. Fields around farmyards tend to have higher P indexes at around 3+.
In terms of other nutrients, 73% of fields are at 2+ or higher for K, while nearly all fields are at optimum for magnesium and sulphate.
That suggests farmers have been following advice from AFBI to apply N products that contain sulphur. However, that advice is likely to be slightly amended going forward. The annual target is to apply 30kg sulphur per ha. That can be achieved in the first fertiliser application in the spring, allowing farmers to spread straight N after that. Only on sandy soils might additional sulphur be required.
Cassidy was also asked about whether individual data would potentially be used against farmers in the future.
“The soil results are only for individual farmers. Results will be used for policy development but only at catchment or regional level. There will be no use of the data for enforcement.
“There is no conspiracy,” she responded.
Results and run-off risk maps
Once a farm is soil-sampled, results will be provided four to six weeks later in the post. Data will also be uploaded to the CAFRE nutrient calculator found within DAERA online services, alongside a map showing areas of the farm where there is a high risk of runoff of nutrients to watercourses.
In these high-risk areas, farmers could potentially look to avail of new incentives coming as part of the Farming With Nature scheme, planting the likes of riparian strips to slow this run-off, suggested Rachel Cassidy. As a minimum, it would be good practice to avoid spreading nutrients in these areas until ground conditions are optimal and grass is actively growing, she suggested.
Once results are received, farmers should register for training via the CAFRE website. This training is available in two phases. The first involves a series of online videos on nutrient management, while the second phase looks at nutrient management planning. The second phase can be done online, although there will also be an option for face-to-face training facilitated by Countryside Services.
Research on Phosphorus levels in Zone 4
Across approximately one third of NI, basalt is the underlying parent material.
These basalt soils are typically red brown in colour and dominate across most of Co Antrim, which is to be the last of four zones to be sampled as part of the SNHS.
According to AFBI soil scientist Dr Suzanne Higgins, basalt soils are characterised by high levels of elements such as iron, aluminium, calcium, magnesium, copper and nickel. Research suggests that the Olsen P soil test (typically used to asses P indexes) may be underestimating the P available to plants within a basaltic soil.
“P is held differently in these soils. We are in the second year of research and it will be completed by 2025-2026 by the time Zone 4 is sampled,” she told the AFBI soil conference.
Role for GPS in nutrient application
During her presentation at the AFBI conference, Dr Suzanne Higgins, also highlighted how research has shown soil texture, clay content and nutrient availability can vary greatly across individual fields – in some cases P has ranged from Index 0 to Index 4.
In addition, studies in 10 silage fields across NI have shown a big variation in grass yields within individual fields, ranging by up to 4t/ha.
She maintained that variable rate spreading of fertiliser and slurry using equipment linked to GPS potentially has an important role in helping farmers avoid overlap of nutrients.
Farms need more manure storage capacity
Across Britain and NI, around 80mt of livestock manure is available and once food waste etc. is added in, the total organic manure to be spread is close to 93mt.
“From a policy perspective that is a big headache,” suggested John Williams from UK agricultural consultancy provider, ADAS.
He warned that spreading late in season increases the risk of losses, especially of nitrogen (N), which is easily washed out of soils. Early in the spring, drained soils might be suitable for travel, but are still wet lower down in the profile and prone to losses of both N and P.
“Two weeks later, there is rain and it is out the drains. That’s why we need more storage – spread when soil and growing conditions are right,” he said.
Role for cover crops in protecting soils
There are many reasons to believe that the arable area in NI will grow into the future, but the challenge is to maintain soil health, especially when grassland is converted over to intensive tillage, suggested Dr Paul Cottney from AFBI Crossnacreevy.
He is a strong advocate of using cover crops to prevent land lying fallow over the winter.
“The main benefit is nutrient sequestration. Overall, cover crops long term can improve soil organic matter, protect against soil erosion and improve soil health,” maintained Cottney. He said it was important to get crops planted early, but acknowledged that autumn weather in NI is “the main barrier” preventing more widespread adoption.