Managing Slurry During Extreme Heat

Recent periods of extreme heat can create several operational, agronomic and environmental challenges for slurry management. During a heatwave, decisions must be made based on crop demand, soil condition, weather forecasts, storage capacity and operator safety. Dry ground alone should never be treated as evidence that conditions are suitable for spreading.

The priority in these circumstances should be to protect slurry’s nutrient value, reduce pollution risk, keep machinery operating safely and avoid unnecessary exposure for staff.

Ammonia loss and nutrient efficiency

The risk of loss increases when air and soil temperatures are high, slurry remains exposed on the surface and wind moves across the application area. Hot, dry afternoons are therefore among the least efficient times to spread.

Where possible, applications should be delayed until cooler conditions return. If spreading is necessary, early mornings or evenings may provide a better opportunity, provided wind speed, soil condition and rainfall risk are also suitable.

Low-emission slurry spreading equipment should be used wherever field and crop conditions allow. Dribble bars apply slurry in defined bands, while trailing shoes place it closer to the soil beneath the crop canopy. Shallow injection reduces contact with the air further, although soil disturbance, power requirements and ground condition must be considered.

Always assess the soil before spreading

Prolonged heat can leave soil dry, compacted, hard or deeply cracked. These conditions may reduce infiltration and cause slurry to remain exposed at the surface for longer.

Deep cracks can also create direct pathways through the soil. Slurry may move below the active root zone or towards drainage systems rather than being absorbed evenly.

Before applying slurry, walk the field and assess surface hardness, cracking, tramlines, gateways, compaction, slope and proximity to watercourses. Field drains and natural run-off routes should also be identified.

A field may appear dry enough to travel on but still be unsuitable for slurry application. Where the soil is severely cracked or capped, delaying the operation may be the safest and most efficient option.

Always match slurry applications to crop demand

Crops under severe heat and moisture stress may reduce growth and nutrient uptake. Applying slurry when the crop cannot use the nutrients effectively can leave nitrogen exposed to loss.

Before spreading, consider whether the crop is still actively growing, whether it is likely to recover following rainfall and whether it has a genuine nutrient requirement. Previous fertiliser applications should also be included in your nutrient plan.

The slurry itself should be properly mixed and sampled before an application rate is calculated. Stored slurry naturally separates, with heavier solids settling and lighter material rising. This can result in inconsistent dry matter and nutrient content throughout the store.

Thorough mixing improves sampling accuracy, pump performance and spreading consistency. Where conditions are marginal, a smaller and accurately controlled application may be more appropriate than a heavy dose. Flow meters can help operators apply a known quantity and produce more reliable nutrient records.

Check the rainfall forecast carefully

Heatwaves often end with thunderstorms or intense local rainfall. This can create a serious pollution risk if slurry has recently been applied to dry, compacted or cracked soil.

A forecast showing rain does not automatically make spreading advisable. Light rainfall may support infiltration, but a sudden downpour can carry slurry and nutrients towards drains, ditches, gateways and watercourses.

The likely intensity, duration and timing of rainfall should be considered alongside field slope and soil condition. If heavy rain is forecast soon after the intended application, spreading should be postponed.

Maintain strict slurry gas precautions          

Hot outdoor temperatures do not reduce the danger of slurry gas.

Agitation can release hydrogen sulphide, methane, carbon dioxide and ammonia. The greatest risk is usually close to mixing points, reception pits, enclosed buildings and poorly ventilated areas.

Before mixing begins, livestock and unnecessary personnel should be removed from the area. Available ventilation points should be opened, access should be restricted, and everyone involved should understand the work plan.

Operators must never enter a slurry tank, reception pit or confined space. They should also avoid leaning over access points or standing close to mixing openings.

Working alone around slurry stores and agitation equipment should be avoided. Extreme heat must never be allowed to encourage shortcuts in normal gas-safety procedures.

Monitor pumps and machinery

High ambient temperatures place extra pressure on engines, pumps and hydraulic systems.

Before starting, check coolant, engine oil, radiator airflow, belts and fuel systems. Dust, grass and crop debris should be removed from cooling grilles to reduce the risk of overheating.

Hydraulic hoses, couplings, clamps, seals and pump components should also be inspected. Worn rubber parts may become more vulnerable when exposed to prolonged heat and direct sunlight.

Stationary pump units should be positioned away from long, dry vegetation or other combustible material. Equipment temperatures should be monitored throughout the job, and machinery should be stopped if overheating is suspected.

Use slurry storage to create flexibility

Adequate slurry storage gives farms the option to wait for better conditions.

Where capacity is limited, operators may feel pressured to spread during unsuitable weather. A well-sized and well-managed store allows applications to be timed around crop need, soil condition and nutrient efficiency instead.

During a heatwave, store levels, freeboard, covers and structural condition should be checked regularly. Clean water should be kept out of the dirty-water system wherever practical, and contingency options should be reviewed before capacity becomes critical.

Storage should be considered as part of the complete slurry system, alongside mixing, pumping, separation and application.

Slurry management during extreme heat should focus on nutrient retention, pollution prevention, operator safety and machinery reliability.

In many cases, delaying an application will be the most effective decision. Where spreading remains necessary, it should be completed during cooler conditions, at a controlled rate and using low-emission equipment suited to the field.

For further advice on adapting your slurry systems and setups for extreme weather, get in touch with us today.