Nitrogen Release Characteristics from Biosolids-Derived Organomineral Fertilizers

Abstract

This study investigated the availability of nitrogen (N) following soil application of a novel biosolids-derived organomineral fertilizer (OMF₁₅—15:4:4) in comparison with urea (46% N). OMF₁₅ is produced by coating biosolids granules (particle size range: 1.10–5.50 mm in diameter) with urea and potash [60% potassium oxide (K₂O)], which increase the concentration of mineral N and potassium (K), respectively, resulting in a balanced fertilizer material suitable for application in cereal and grass crops. The study comprised two soil types of contrasting characteristics which were incubated over a period of 90 days at 25 °C and maintained near field capacity. Nitrogen was applied at rates equivalent to 0 (control), 150, and 300 kg ha⁻¹, and soil mineral N measured routinely using standard laboratory techniques. Results showed that the majority of N was released from OMF₁₅ within 30 days from application (range: 40% to 72% of total OMF₁₅-N applied) with a further 10% to 28% in the following 60–90 days. OMF₁₅ required an accumulated thermal time of 2250 degrees-day to release between 68% and 79% of the total OMF₁₅-N applied. From this, it was inferred that mineralization of the organic-N fraction in OMF₁₅ is likely to progress beyond harvest of winter cereal crops in-field conditions in England. The results of this study aided the development of fertilization strategies for the best use of OMF in winter cereal and grass crops.

Keywords:

• Biosolids granules
• nitrogen availability
• organomineral fertilizers (OMF)
• soil N dynamics
• winter cereal and grass crops

Additional information

Funding

This research received funding from the European Union Seventh Framework Programme (FP7-ENV.2010.3.1.1-2 ENV) under grant agreement no.: 265269 (http://www.end-o-sludg.eu/). The article represents the opinion of the authors and does not necessarily represent the view of the European Union or United Utilities Group PLC. The authors are grateful to United Utilities Group PLC, The Engineering and Physical Science Research Council, and Cranfield University for financial and operational support.