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Objective: Supply Nutrients
The management strategy that best suits your need will depend on your goals. An important differentiation is between strategies where the goal is improvement of soil structure and related properties, compared to strategies that aim to maximise nutrient supply or maintain and improve soil organic matter the longer term.
How to improve the supply of nutrients from your soil organic matter?
Organic resources such as manures produced on the farm (slurries, FYM and poultry manures), or supplied from other sources such as treated sewage sludge (or "biosolids") and some industrial "wastes", can provide valuable sources of both organic matter and plant nutrients. Often this will result in savings on inorganic fertilisers as well as building up soil organic matter.
The amount of nutrients supplied varies depending n the nature of the organic resource used. It is often useful to consider the relative amounts of carbon and nitrogen (or other nutrients) in the organic matter. This is known as the C:N ratio. Fresh animal manures such as slurries and poultry manures are relatively high in available nitrogen and other nutrients, so have a low C:N ratio compared with more heavily bedded manures such as cattle FYM. Materials with a low C:N ratio will release nutrients more quickly. Resources such as cereal straw have little available nitrogen, and can even draw nitrogen fand other nutrients from the soil as microbes meet their own nutrient requirements while breaking the straw down. Nitrogen becomes available in the longer term when the microbes themselves are recycled. A quick guide to the C:N ratio of commonly used organic resources can be found in our brochure "Profiting from soil organic matter".
The tabs above provide links to examples of the strategies that can be considered to improve nutrient supply. You'll find links to individual case studies where where changes in organic matter management led to improved farm profitability. If you wish to undertake a more detailed assessment of whether your current management strategy returns sufficient organic matter you can work with one of our Associates to analyse your current soil organic matter status. We use two key measures the first is to compare your currently soil organic matter levels against the expected range "Manageable Range", provide an indication of potential to increase soil organic matter content. By measuring your "Carbon Status" we are able to assess whether current levels of organic matter return will maintain your soil organic matter levels.
Important Regulations and sources of information
Good information to help with nutrient planning in the use of most organic manures is available in Fertiliser Recommendations for Agricultural and Horticultural Crops (RB209), which forms the basis of useful software for assisting in fertiliser planning, such as MANNER and PLANET. This will help in considering both the total nitrogen content of the organic resource, and the available nutrients at the time and method of application. For other types of organic resources, analysis of nutrient composition will be a requirement of the supplier in order to gain an Environment Agency exemption or licence for land spreading (e.g. sewage sludge or ˜biosolids", composts and industrial wastes). Information and support for this process is available from NetRegs (www.netregs.gov.uk).
Organic resources have the potential to present an environmental risk if not used appropriately. Guidance on avoiding pollution is given in The Water Code (MAFF PB0587) and The Air Code (MAFF PB0618). Introduction of the Single Payment Scheme also brings legal requirements about the use of sewage sludge and organic manures in NVZs into Statutory Management Requirements for the scheme, and farmers need to ensure that they comply with the limits and conditions set for use of these resources, described in the Single Payment Scheme Cross Compliance Handbook for England 2006 edition (MAFF PB11305). Nitrogen in particular is potentially highly leachable, and for this reason in Nitrate Vulnerable Zones there is a limit to the amount of total nitrogen that should be applied, and closed periods for spreading on lighter land and shallow soils. These practices are detailed in NVZ Action Programme (Guidelines for Farmers in NVZs, MAFF PB3277). In some cases it may also be necessary to limit applications of organic resources to avoid excessive enrichment of soil phosphate levels. The Defra webpages provide further information and links to downloadable versions of the documents described above (www.defra.gov.uk).