Assessment of plant nutrients losses during drying and granulation of poultry manure with amended with wheat straw and natural peat
¹Institute of Soil and Plant Sciences, Latvia University of Life Sciences and Technologies, Liela iela 2, LV-3001, Jelgava, Latvia
²Institute of Engineering and Energetics, Latvia University of Life Sciences and Technologies. Cakstes blvd. 5, LV-3001, Jelgava, Latvia
³Institute of Computer Systems and Data Science, Latvia University of Life Sciences and Technologies, Liela iela 2, LV-3001, Jelgava, Latvia
*Correspondence: aleksandrs.adamovics@lbtu.lv
Abstract:
This study evaluated nitrogen (N), phosphorus (P) and potassium (K) losses during the drying and granulation of poultry manure (PM) and assessed the effectiveness of short-term thermal pre-treatment and organic amendments in improving nutrient retention. Seven 2.0 kg samples were prepared, comprising two samples of pure poultry manure, two PM mixtures containing 2.5 and 7.5% wheat straw (WS), and three PM mixtures containing 7.5, 15.0 and 22.5% natural peat (NP). The samples were dried to approximately 25% moisture content using either low-temperature drying at 24 °C or a combined drying regime consisting of pre-drying at 70 °C for 1 h followed by drying at 24 °C. The dried materials were granulated using a pellet press equipped with a 6 mm die, after which the granules were further dried to a final moisture content of 8-10%. The nutrient contents of both the raw materials and the produced granules were determined in an accredited laboratory. The drying regime significantly influenced nutrient retention. Granules produced from untreated poultry manure dried entirely at 24 °C exhibited nitrogen and phosphorus losses of 0.73 and 0.23 percentage points, respectively. Applying a 1 h pre-drying treatment at 70 °C reduced nitrogen losses to 0.32 percentage points and phosphorus losses to 0.12 percentage points. No detectable nitrogen losses were observed in granules produced from poultry manure amended with wheat straw or natural peat, except for a slight reduction in the treatment containing 22.5% peat. Phosphorus losses were eliminated in mixtures containing 7.5% wheat straw and 7.5 or 15% peat. Potassium losses were negligible in all treatments, with only a minor decrease observed in granules containing 22.5% peat. The results demonstrate that short-term high-temperature pre-drying effectively improves nutrient retention during poultry manure granulation. Incorporating wheat straw or natural peat into poultry manure further reduces nutrient losses during drying and pellet production, thereby improving the fertiliser value of the final granulated product.
Key words:
granulation, nitrogen, nutrient retention, organic fertiliser, Phosphorus, potassium, poultry manure