Profitable farming requires continued development and use of a wide range of skills. Good nutrient management is an important aspect of this and can contribute to business efficiency and reduce environmental impacts
The Nutrient Management Guide (RB209) helps you make the most of organic materials and balance the benefits of fertiliser use against the costs - both economic and environmental. It explains the value of nutrients, soil and why good nutrient management is about more than just the fertilisers you buy; it can save you money as well as help protect the environment.
Regulation, codes of practice and assurance schemes
Organic materials applied to agricultural land, such as livestock manures, biosolids, composts, anaerobic digestates and waste-derived materials, are valuable sources of most major plant nutrients and organic matter. Careful recycling to land allows their nutrient value to be used for the benefit of crops and soil fertility, which can result in large savings in the use of manufactured fertilisers. However, organic materials can present a considerable environmental risk if not handled carefully. Guidance on avoiding pollution, including manure management planning, is given in Protecting our Water, Soil and Air: A Code of Good Agricultural Practice for farmers, growers and land managers. For all organic materials, it is important to check their use complies with contracts, relevant assurance schemes and animal by-product regulation.
Nitrate Vulnerable Zones (NVZs)
Northern Ireland www.daera-ni.gov.uk/articles/nitrates-directive
Sampling livestock manures
For nutrient management planning, it is important to know the nutrient content of manures applied to land. The tables in this section give typical values of the total nutrient content of manures based on the analysis of samples from a wide range of sources. However, the nutrient content of livestock manures is likely to vary significantly, depending on the source and management of the material. For example, the nutrient content will be influenced by farm-specific feeding and bedding practices, and digestate nutrient content will vary on a site-by-site basis depending on feedstock used in the digestion process.
The livestock manures produced may have a nutrient content that is consistently different from the values given in the tables. It can, therefore, be worthwhile having the nutrient content of representative manure samples determined by analysis. Rapid on-farm kits (e.g. Agros, Quantofix) can reliably assess the ammonium-N content of liquid manures (e.g. cattle slurries and digestates), but laboratory analysis is necessary for other nutrients. Laboratory analyses should include dry matter (DM), organic matter, total nitrogen (N), total phosphate (P2 O5 ), total potash (K2 O), total sulphur (SO3 ), total magnesium (MgO) and ammonium-N (NH4 -N). Additionally, nitrate-N (NO3 -N) should be measured in well-composted farmyard manure (FYM) and poultry manures, and uric acid-N in poultry manures.
Hydrometers can be used to measure the dry matter content of liquid manures. Where dry matter varies, adjust previous laboratory results or the typical values in the following tables. The nutrient content of liquid manures can vary considerably within a store, due to settlement and crusting. In particular, pig slurry can ‘settle out’ in storage, with a higher dry matter layer being at the base of the store and a lower dry matter layer occupying the mid/upper levels, which, during store emptying, can markedly affect slurry dry matter and associated nutrient contents.
Similarly, the composition of solid manure in a heap can vary depending on the amount of bedding and losses of nutrients during storage. If stored materials are to be analysed either in a laboratory or using a rapid on-farm method (e.g. using Agros or Quantofix slurry-N meters), it is important that the sample taken represents an ‘average’ of what is found in the heap or store. It is important that sampling is carried out carefully and that representative samples are provided for analysis. The optimum sampling frequency will vary depending on how manures are managed on the farm, but at least two samples per year are recommended, coinciding with the main spreading periods.
Taking a representative sample of a liquid manure
• Collect at least five subsamples of two litres each and pour into a large container
• Thoroughly mix the bulked sample
• On-farm rapid analysis of slurries should be carried out immediately
• If a sample is to be sent to a laboratory, 250 ml should be dispatched in a clean, screw-topped, plastic container (normally available from the laboratory)
• Leave 2–3 cm of airspace to allow the sample to be shaken in the laboratory
• Label the sample clearly, providing as much information as possible
• As soon as possible, send the sample first class to the laboratory (prepaid envelopes are normally available from the laboratory)
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