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 more than adequate amounts of phosphorus and potassium and reduce nitrogen 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 fits crop requirements and then only to top up with bagged fertiliser if necessary.

The amount of nitrogen available to a crop increases in the spring. 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 is relatively easy to calculate. Typical values based on average nutrient content, taken from the AHDB Nutrient Management Guide (RB209), are shown below. It can be harder to quantify the value of the organic matter, but research has shown that regular addition of manures, especially farmyard manure, improves soil structure, workability, water infiltration and drainage.

Table 1. Typical financial value of livestock manures

Note: The values assume that the manure is spread in the spring onto a medium soil at P and K Index 2 and incorporated within six hours. Purchased fertiliser price assumptions based on a 12-month average: Nitrogen (N) = £2.24/kg, Phosphate (P) = £1.71/kg, Potash (K) = £1.13/kg. Prices correct at the time of publishing March 2023.

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

• Don’t waste money on bagged fertiliser
• Take account of the nutrient content of livestock manures and only top up with fertiliser when needed
• Find out the nutrient value by sending a sample to a laboratory for analysis (or use the average values published in Section 2: Organic materials of the AHDB Nutrient Management Guide (RB209)
• Create a manure management plan to identify fields or parts of fields where spreading restrictions apply
• Most assurance schemes require you to create a manure management plan
• Maximise availability of nutrients by applying manures in the spring and incorporate them as soon as possible
• Track levels of soil organic matter by asking the laboratory to test it for you when you send in a soil sample for routine analysis (P, K, Mg, pH)

The environmental impact should also be considered. Poor manure management can cause nutrients and other pollutants to get into watercourses or escape as harmful gases. This can happen in a variety of ways:

• Runoff: when rainfall does not infiltrate into the soil, instead running across the surface, carrying nutrients and soil into watercourses
• Leaching: when soluble nutrients, such as nitrate, pass through the soil and into watercourses as water drains
• 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 is a relatively simple and convenient arrangement. However, agreements can 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.

The approximate value of straw and farmyard manure, based on average nutrient content taken from the AHDB Nutrient Management Guide (RB209), is presented in Table 2. However, while soil improvement provided by farmyard manure adds extra value to the material, it is not so easily quantified.

Table 2. Approximate value of straw and farmyard manure

Note: Values based on purchased fertiliser price averaged over a 12-month period: Nitrogen (N) = £2.24/kg, Phosphate (P) = £1.71/kg, Potash (K) = £1.13/kg. Prices correct at the time of publishing March 2023.

To order a hard copy of the Livestock and the arable rotation guide, please contact publications@ahdb.org.uk or call 0247 799 0069.