Livestock manures for the arable rotation

Learn more about the benefits of livestock manures for arable systems. You will find information on muck-for-straw deals and the financial value of livestock manures.

Livestock manures are an excellent source of valuable nutrients and organic matter. They can provide nitrogen, phosphorus and potassium and reduce fertiliser bills.

Integrating them fully into nutrient management plans is key to the success of using manures. It is critical that manures are used in the way that best meets crop requirements and then use inorganic ‘bagged’ fertiliser to meet crop requirement when needed.

The amount of nitrogen available to a crop increases when soils are warm and conditions favourable, often in the spring. Applications can also be made in the autumn where there is a crop requirement and soil conditions allow.

Applying manures at this time of year supplies nutrients when crops need them most and reduces the risk of nitrate leaching.

The financial value of the nutrients contained in manures can be calculated using typical average nutrient values found in RB209 Section 2 Organic materials if actual on-farm analyses are not available.

Use the AHDB organic materials value calculator tool for economic support to account for the nutrient value (nitrogen, phosphate and potash) from biosolids, manure, slurry, digestate and compost in specific situations.

While it can be hard to quantify the value of organic matter, research has shown that regular addition of manures, especially farmyard manure and composts, improve soil structure, workability, water infiltration and drainage.

When planning the use of manures, there are some key practical considerations to ensure full financial value is gained:

• Create a nutrient management plan that fully integrates the nutrient value of manures and slurries to meet crop needs
• Track levels of soil organic matter by requesting it along with the regular routine laboratory soil analysis (P, K, Mg and pH) used to guide nutrient applications
• Find out the manure nutrient value by sending a sample to a laboratory for analysis, or use the average values published in Section 2 of the AHDB Nutrient Management Guide (RB209)
• Take account of the nutrient content of livestock manures and use inorganic fertiliser only when needed to meet crop requirements
• Maximise availability of nutrients by applying manures in the spring or autumn when soil conditions are suitable and there is a crop requirement. Incorporate as soon as possible
• Create a manure management plan to identify fields or parts of fields where spreading restrictions apply and target fields with low organic matter
• Many assurance schemes require a manure management plan

Poor manure management not only reduces efficiency of nutrient use but results in nutrients being lost to watercourses and into the air, causing environmental damage. This can happen in a variety of ways:

• Runoff: when rainfall does not infiltrate the soil but instead runs across the surface, carrying nutrients and soil into watercourses
• Leaching: when soluble nutrients, such as nitrate, pass through the soil and into watercourses
• Ammonia volatilisation: when nitrogen in manures is converted into ammonia gas and ammonia is initially lost to the atmosphere then deposited on the soil or into watercourses

When nutrients, such as phosphate and nitrate, enter watercourses they can cause algae and plants to grow rapidly and then die when the environment becomes overcrowded.

This can lead to oxygen depletion and the watercourse to become lifeless. Ammonia can affect public health as well as causing acidification of soil and watercourses.

Exchanging muck for straw can be a relatively simple and convenient arrangement. However, agreements vary significantly.

The arable business provides straw for bedding. In return, the stockperson provides an enhanced product that is rich in nutrients and organic matter.

The key things to agree on are how much muck and straw will change hands and who will pay for and carry out baling, transportation and spreading.