‘Saturated to waterlogged’ land reduces opportunities for safe slurry spreading – Teagasc

Thomas Lyons

The long term average (LTA) rainfall for Westmeath in the month of January showed that 117.8 millimetres fell, representing 128% of its LTA for the month.

The data comes from the Met Éireann weather station situated west of the town, which has been automated since 1998.

Rainfall amounts over the last week were above normal across most of Leinster, and two or three times the normal amount of rain fell in parts of the east and southeast.

That has resulted in the soils in the midlands becoming “saturated to waterlogged”, with poor trafficability for machinery.

Catherine Kilmartin of the Mullingar Advisory Office of Teagasc says the current spell of prolonged rainfall is putting major pressure on slurry systems: “Tanks are filling faster than normal, opportunities to spread safely are limited, and the risk of nutrient losses to water is high.

“Climate projections suggest wetter winters and more intense rainfall events will become more common. That makes it even more important to manage slurry carefully – both in the short term and through longer-term planning.”

Catherine, who is from Kinnegad, is the Signpost Climate advisor for the Agriculture and Food Development Authority in the Westmeath, Offaly, Cavan, Monaghan region. The agriculture specialist indicated the factors to be considered for the management of slurry in prolonged wet weather.

“Slurry is a valuable resource, but timing is everything,” she said. “Slurry remains one of the most valuable nutrients on Irish farms. The nitrogen (N), phosphorus (P) and potassium (K) in 1,000 gallons of typical cattle slurry is worth approximately €28, that is similar to a bag of 9-5-32.”

Given the challenges presented by the current weather, Catherine says there are a number of key considerations: “Only spread slurry when ground conditions are suitable, always protect water by maintaining buffer zones, and if slurry storage is regularly under pressure, consider increasing capacity and reducing the volume of clean water entering tanks.”

The Met Éireann data is one thing, but for farmers trying to balance sodden fields with filling slurry tanks is another.

“With tanks filling rapidly on many farms, decisions need to be made carefully. Protecting water quality and staying within regulations must always come first,” Catherine said. “Even though we are in the open spreading period, it’s illegal to spread slurry or farmyard manure under certain conditions.”

Those conditions include when land is waterlogged, flooded or likely to flood; when it is snow-covered or frozen; and when heavy or extreme rainfall is forecast within the next 48 hours.

“Spreading in those conditions greatly increases the risk of nutrients being washed into drains, streams and rivers. The advice is to choose the lowest-risk fields, if slurry must be spread and conditions allow, target only the driest and lowest-risk fields on the farm,” she said.

Those lowest-risk fields typically have free-draining soils, good grass cover, have an active nutrient demand and good soil pH and a requirement for P and K. Farmers are advised to avoid locations that greatly increase the risk of runoff and nutrient loss. They include: low-lying or poorly drained areas; wet patches; field corners; or any areas with a direct connection to drains or watercourses.

The Teagasc advisor gave further guidance: “Apply light rates and use the right equipment. At this time of year, tanks do not need to be fully emptied. Often, removing a few loads can ease pressure and buy valuable time while waiting for better weather and ground conditions.”

Applying slurry at light rates means that there is reduced runoff risk and improvement in nutrient uptake, giving greater flexibility during unsettled weather. Farmers stocked over 100kg N/ha must use Low Emission Slurry Spreading (LESS) equipment. LESS places slurry closer to the soil surface, reduces ammonia losses and allows spreading on slightly heavier grass covers compared to splash plates.

Farmers with water courses on their land will know what factors to take into consideration: “It’s about respecting buffer zones and critical source areas. Buffer zones are one of the most important protections for water quality. All streams, drains and watercourses on the farm should be clearly identified, and the required 5m or 10m buffer zones strictly observed.

“Extra care is needed around critical source areas (CSAs). Those are usually low-lying parts of fields where water collects and flows directly to drains or watercourses. Avoid spreading in those areas whenever possible.”

The precipitation of the last couple of months has indicated the need to consider longer-term actions on farms. They could include a review of storage capacity.

Westmeath and Offaly are both in Zone A for the prohibition period. Slurry spreading closes on October 1, while Farmyard Manure spreading closes on November 1, with no spreading of either until January 15.

“The slurry storage requirement is 18 weeks, which runs from October 1 to approximately February 3,” Catherine said. “This explains why tanks often remain under pressure well into late January or early February – especially in wet years when ground conditions delay spreading.

“Farmers should assess whether their storage genuinely covers that period without relying on emergency spreading. Teagasc recommend planning for an additional 2–4 weeks of buffer capacity, where possible.”

Regular pressure on tanks usually points to either insufficient storage capacity, or too much clean water entering slurry stores. Farmers are advised to keep clean water out of slurry tanks: “Rainwater can significantly reduce available storage. For example, in Westmeath, based on average rainfall, a 10m × 10m uncovered tank can collect over 8,000 gallons of rainwater during the 18-week closed period. That is equivalent to the slurry storage requirement of around seven dairy cows or eight suckler cows,” Catherine said.

Covering tanks and diverting roof water away from slurry stores can make a big difference to available capacity.

Recognising the value of slurry is one of the factors farmers must consider. Used correctly, it can replace significant amounts of chemical fertiliser.

“Protecting this resource – and investing in adequate storage – pays off in the long term. It allows slurry to be applied at the right time, in the right place, and under the right conditions, while reducing fertiliser costs,” Catherine explained. With prolonged wet periods becoming more common, the message is simple: “Farmers can reduce pressure during difficult periods, protect water quality and build greater resilience into their slurry systems for the future by: only spreading in suitable conditions; targeting the right fields; applying light rates; respecting buffer zones; and keeping clean water out of tanks.”