Keywords: Nutrient recommendations, Organic manure nutrients, Fertiliser use, Fertiliser efficiency, Environmental pollution, Soil nitrogen.
This paper describes the main aspects of the revised recommendations contained in the 7th edition of ‘Fertiliser Recommendations for Agricultural and Horticultural Crops (RB209)’ produced by the Ministry of Agriculture, Fisheries and Food (MAFF) for England and Wales. RB209 gives specific recommendations for the use of lime, N, P, K, Mg, S, Na fertilisers and organic manures for a wide range of field crops and grassland based on relevant research data and practical experience. It also describes the principles of crop nutrition and gives guidance on important related topics, such as soil sampling methods and fertiliser application. There are several significant improvements compared to the previous edition. A new Soil Nitrogen Supply (SNS) Index system has been devised to estimate the amount of soil nitrogen likely to be available in different field situations using information for previous cropping and manuring, soil type and winter rainfall. Each of the 7 SNS Indices are defined in terms of a quantity of soil nitrogen available for crop uptake during the growing season. The SNS Index can therefore be determined using the results of analysis for soil mineral nitrogen (SMN) taking account of the estimated crop nitrogen content at the time of sampling and mineralisable nitrogen. Analysis for SMN is recommended where soil N residues are likely to be large or uncertain. All crop specific nitrogen recommendations are related to the SNS Index for the field. For winter wheat, information for grain nitrogen concentration is introduced as a factor for adjusting nitrogen rates. Expected yield is no longer used to adjust winter wheat or oilseed rape recommendations. Using a dataset of 264 response trials, the revised nitrogen recommendations for winter wheat are within +/- 30 kg/ha of the measured economic optimum nitrogen rate in 43% of cases. Phosphate and potash recommendations are based on the amount needed for crop response or, where no response is expected, for maintaining soil nutrient Indices by replacing the nutrients removed in crop produce. Typical values are given for the nutrient content of crop materials. Sulphur is recommended for cereal, oilseed rape and grass silage crops based on soil type, location and tissue analysis information. Significant improvements have been made for assessing the nitrogen value of farm manures and sewage sludges. The key factors are manure type, readily available nitrogen content, time and method of application, soil type and winter rainfall. Analysis of manures is recommended using rapid on-farm (for ammonium-N) or laboratory methods. The tabular recommendations in RB209 account for over 50% of the variability in crop-available nitrogen though the computerised MANNER system is even more accurate.
Peter M.R. Dampney, ADAS Boxworth Research Centre, Cambridge, UK
39 pages, 11 figures, 14 tables, 45 refs.