Maximising the Benefits of Slurry Application on Tillage Farms

Michael Hennessy tells us many farmers are eager to start applying slurry now that the spreading window has reopened. He emphasizes the need for an up-to-date nutrient management plan and highlights how well-managed slurry can improve soil health and ensures future productivity.

Despite the brief cold snap and some snow in parts of the country, this winter’s weather has generally been kind. As animals have spent the past few months indoors, many farmers are eager to start applying slurry now that the spreading window has reopened. A drive through the countryside today revealed significant slurry activity, predominantly on grassland. However, tillage land is a natural home for much of this valuable resource and offers significant benefits when managed correctly.

Plan Before You Spread

Slurry application on tillage land cannot be done on a whim. Farmers must consider the total nitrogen (N) and phosphate (P) allowances for their farm to avoid breaching regulations. Any tillage farmer accepting slurry needs an up-to-date nutrient management plan (NMP), which factors in:

• Soil indices for N, P, and K.
• Crops planted or due to be planted.
• Previous yields.
• Existing livestock on the farm

This NMP calculates the farm’s total nutrient allowance, balancing inputs from chemical fertilisers and organic manures. Be aware that all fertilisers, both chemical and organic, must be documented: chemical fertiliser purchases are recorded in the fertiliser register, and slurry imports must be reported to the Department of Agriculture within four days of movement.

Why Organic Manures Are Worth It

While the compliance requirements may seem burdensome, organic manures offer advantages beyond N, P, and K supplementation. They contribute valuable carbon and microbial life to the soil, enhancing its structure and resilience against extreme weather conditions like drought or extended wet periods. Farmers who regularly use organic manures often report consistently high yields, demonstrating their long-term value.

Preparing for Slurry Imports

If you plan to import organic manures this year, start preparations now. Contact your local Teagasc advisor to arrange an appointment to complete or update your NMP. Before the meeting, ensure you have the following:

1. Soil sample results (no older than four years).
2. Details of crops sown and planned for this season.
3. Yield records for the past three years (adjusted to 20% moisture).

High-yielding crops have additional N and P allocations, which can be critical for meeting your farm’s needs.

Understanding Slurry Composition

Not all slurries are equal, and knowing the dry matter (DM) content is essential for effective use. For example:

• Pig slurry with 4% DM contains the following per m3 (or per 1,000 gallons) ; N =  4.2kg (38 units), P =0.8 kg (7 units /1,000 gal)  and K = 1.9 kg (17 units/1000 gal)  
• Pig Slurry with 2% DM contains the following per m3 (or per 1,000 gallons) ; N =  2.5kg (22 units, P =0.5 kg (4.5 units /1,000 gal)  and K = 1.2 kg (11 units/1000 gal)

Note: for the above slurries not all of the nutrients are available and calculations for the Nitrates Directive are based on 50% availability for Nitrogen – therefore for every 11m³ or 1,000 gallon of 4% DM imported,  this adds 23kg (19 units) of nitrogen to the farm totals.

This variation significantly impacts transport costs, and substitution potential for chemical fertilisers. Regularly measuring the DM content during spreading ensures consistent application across fields and provides the nutrients your crops require.

Regulatory Compliance

For farmers importing slurry, the book values are used for nutrient calculations, not the real or measured values, when totting up the totals for the nitrates regulations. Importing low-DM or dilute slurry can leave you short on nitrogen and phosphate and potassium, potentially affecting crop yields. Proper planning and testing are essential to make the most of slurry while staying within your farm’s nutrient allowances.

Key Takeaways

• Slurry is a valuable resource for tillage soils but requires careful planning and compliance with regulations.
• An NMP is mandatory and ensures you balance nutrient inputs effectively.
• Understanding the nutrient content of slurry is essential for maximising its value and meeting crop requirements.
• Work with your Teagasc advisor to create a tailored plan for your farm.

Slurry application on tillage land is not just about meeting immediate nutrient needs—it’s an investment in soil health and future productivity.