ARCHIVE: Fertiliser Manual (RB209)

Introduction


Organic manures applied to agricultural land may be produced on the farm (slurries, farmyard manures (FYM) and poultry manures) or supplied from other sources such as treated sewage sludges (commonly called biosolids), composts and industrial ‘wastes’ such as paper crumble, food industry by-products etc. These 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 inorganic fertilisers. In the case of phosphate, such recycling helps conserve the limited global resource of this essential crop and animal nutrient.

Organic manures, particularly solid manures, add useful amounts of organic matter to soils. Their use can improve water holding capacity, drought resistance and structural stability, as well as the biological activity of soils. These improvements are most likely to be achieved where regular manure applications are made. The maintenance and enhancement of soil organic matter levels is a cross compliance requirement of farmers receiving the Single Payment. Care should be taken during application not to cause soil compaction, which may have a detrimental effect on crop growth and increase the risk of surface run-off.

Organic manures can present a considerable environmental risk if not handled carefully. Guidance on avoiding pollution is given in Protecting our Water, Soil and Air: A Code of Good Agricultural Practice for farmers, growers and land managers (Defra, 2009). In Nitrate Vulnerable Zones (NVZs), the amount of total nitrogen in applied organic manures must not exceed 250 kg/ha in any 12 month period at the field level. In some situations, lesser amounts may be appropriate. For example, the amount of crop available nitrogen supplied by organic manures should not exceed the amount of nitrogen recommended for the next crop. In some fields, it may be necessary to limit organic manure applications in order to avoid excessive enrichment of soil phosphorus levels. In NVZs, it is mandatory to follow the NVZ Action Programme which includes spreading rate and timing restrictions on the application of organic manures. Guidance booklets are available from Defra (see Section 9).

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