Applying sewage sludge to land is one way growers can increase the soil organic matter content of their land in a bid for better yields, and it can help cut nitrogen fertiliser use by up to 20%.
This water waste by-product is a relatively cheap yet effective alternative to conventional chemical fertilisers, which also brings the benefits of added soil organic matter.
Despite being commonly referred to as “sludge”, it is a solid similar to compost and results from the sewage treatment process carried out at waste water facilities. Here Crops asks an agronomist, contractor and grower for their experiences.
Emma Revis, contract manager, Robinson Contract Services
Based in Brandesburton, 15 miles north of Hull, Robinson Contract Services is the sole supplier of sewage sludge products in the Yorkshire Water region, distributing around 350,000t every year.
They manage the entire process from the treated waste leaving the water company to it being applied on the land in some cases.
Contract manager Emma Revis says sewage sludge can represent a cost effective way of improving soil health.
“For many customers this is a way of incorporating organic matter as well as nitrogen, potassium, phosphate and sulphur into their soils.”
Sewage sludge products are usually sold between £2 and £3/t, depending on haulage costs.
Ms Revis explains that sludge is becoming increasingly popular with growers because they see they are getting more for their money when compared with a bagged fertiliser.
“The farmer normally only pays for about a quarter of the nutrient value of the product compared with buying fertiliser from the bag and this does not take into account the nutrient value of the organic matter,” adds Ms Revis.
Regulations mean all land that is destined to have the sludge applied needs to be tested for its pH and concentration of elements like copper, zinc and lead.
Spreading must be carried out in accordance with “The Safe Sludge Matrix”, which determines the acceptable level of sludge treatment for combinable and animal feed crops. Growers are also urged to check their contract, for example with their maltster
|Nutrient||Applied total nutrient (kg/ha)|
|Typical sewage sludge application rate 20t/ha|
Philip Vickers, independent agronomist
Lincolnshire-based independent agronomist Philip Vickers says that progressive arable farmers are now starting to recognise the long-term issues of low soil organic matter.
“This is a problem that has built up over time, where we’ve been taking more out of the soil than we’ve been putting in. Soil organic matter levels have been falling and we are just beginning to realise the long term implications of this.”
Mr Vickers sees low soil organic matter content as a big issue that is set to stay with growers unless careful consideration is given to correcting the problem.
He explains that reversing this trend is an on-going process and predicts that in the next decade all farmers will need to consider ways of improving soil health or face a future with crops falling short of their true potential yield.
“The key benefit of applying products like farmyard manures, sewage sludge, compost and anaerobic digestate is that you are not only fertilising your crop, but you are also returning organic matter to the soil.
“I think of organic matter as the glue that holds the soil and nutrients together. Crops do so much better when the organic matter is increased and this is particularly noticeable in the extremely wet or dry years,” he says.
“In practice I have seen wheat yields increase by up to 2t/ha following an application of sludge products or farmyard manures.”
He says growers do need to be wary when applying biosolid products like sewage sludge or farmyard manures as excessively high nitrogen levels can cause crop lodging and careful nutrient and PGR (plant growth regulators) planning is essential.
“This, along with the paperwork and the risks of compaction has put some growers off. It’s all about risk management and ensuring you’re doing more good than harm,” he says.
Tom Bayston, Pollington Grange Farm, near Goole, East Yorkshire
Grower Tom Bayston has spread sewage sludge on parts of his 400ha farmland in East Yorkshire for the past three years.
In his first year of using the product, Mr Bayston only applied it to a small area of land and has steadily increased the area he spreads each year.
This year he applied the product to about half of his land between harvest and drilling.
“The main reason we chose sludge was because we wanted to keep improving the fertility of the soil in the long run. We used to keep cattle, pigs and poultry and we would spread the manure.”
“Once we decided not to keep any animals we still wanted the long lasting fertility benefits of spreading manure and the sludge has really delivered.”
He grows winter wheat, winter barley, winter oilseed rape, potatoes and sugar beet, plus a small area of triticale on a mix of sandy loam and heavy clay land.
He says sludge is an easy maintenance product because it can be dumped on farm without the need for any special previsions or containers. He adds that at £2/t delivered, it’s cost effective too.
Mr Bayston has found that in some fields he can delay the first application of nitrogen and use less of it because soil tests still show high levels.
“On average I’d say we are saving about 30kg/ha on nitrogen as a result. That represents a 15-20% saving so it’s certainly significant.”
He applies sludge to all of his wheat, barley and oilseed rape crops with average yields at 9.5t/ha, 8.5t/ha and 4.4t/ha respectively.
Although he cannot categorically say how much his yields have increased since applying sludge products, Mr Bayston explains that the nutrient-rich sludge noticeably enhances the health and appearance of the crop in the early growth stages.
“It’s about more than yield increases though, it’s about making sure the land continues to be fertile for the future,” he says.
Sewage sludge – things to consider
|Revives soil health, adds nutrients and increases organic matter content||Excessive nitrogen can cause lodging|
|Can boost yields by 1.5t/ha||Paperwork and regulations|
|Cheap compared to bagged fertiliser||Risks of compaction|
|Potential for nitrogen cost savings, cutting bagged N use by 15-20%|