Assessing the performance of phosphorus-saturated ochre as a fertilizer and its environmental acceptability

• Published in: Soil use and management 2005-06, Vol.21 (2), p.231-239
• Main Authors: Dobbie, K.E, Heal, K.V, Smith, K.A
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; barley; Betula pendula; bioavailability; Biological and medical sciences; clay loam soils; crop yield; fertilizer application; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; grasses; Hordeum vulgare; iron oxides; metals; mine spoil; Nitrogen, phosphorus, potassium fertilizations; Phosphorus fertilization; phosphorus fertilizers; Picea sitchensis; soil chemical properties; soil pH; soil pollution; Soil-plant relationships. Soil fertility. Fertilization. Amendments
• ISSN: 0266-0032; 1475-2743
• DOI: 10.1079/SUM2005314

Flooding of abandoned coal mines often causes discharges of iron-rich drainage water into the environment. Treatment of these discharges results in the formation of ochre (hydrous iron oxides) for which no end-use has been identified. Ochre effectively adsorbs phosphate from solution and thus could be used for remediation of waste waters. The resulting P-enriched ochre could then potentially be recycled as a P fertilizer. Pot and field experiments were set up to assess performance and environmental acceptability of ochre in this role, using grass and barley as test crops, as well as birch and spruce tree seedlings. Soils and plant materials were analysed for total and available P, total metals and pH. Results showed that P-saturated ochre functioned as a slow-release P fertilizer, and in the short term was as effective as conventional P fertilizer in maintaining crop yields. It also raised soil pH, and did not pose any significant problem through introduction of potentially toxic trace metals into the soil.