The European dairy industry generates large volumes of wastewater from milk and dairy food processing. Removal of phosphorus (P) by complexing with metal (e.g., aluminium, calcium) cations in P rich sludge is a potential P source for agricultural reuse and P recycling. However, there is a significant knowledge gap concerning the plant availability of this complexed P in comparison to conventional mineral P fertiliser. The current absence of information on plant P bioavailability of dairy processing sludge (DPS) limits the ability of farmers and nutrient management advisors to incorporate it correctly into fertiliser programmes. The present study examined the most common types of dairy sludge\uffe2\uff80\uff94(1) aluminium-precipitated sludge (\uffe2\uff80\uff9cAl-DPS\uffe2\uff80\uff9d) and (2) calcium-precipitated lime-stabilised sludge (\uffe2\uff80\uff9cCa-DPS\uffe2\uff80\uff9d) at field scale to assess P availability in grassland versus mineral P fertiliser over a growing season. The experimental design was a randomised complete block with five replications. Crop yield and P uptake were assessed for 4 harvests. The initial soil test P was at a low level and the experimental treatments were super phosphate at 15, 30, 40, 50 and 60 kg P ha\uffe2\uff88\uff921, two dairy sludge applied at 40 kg P ha\uffe2\uff88\uff921 (comparison was made with mineral P at same application rate) and a zero P control applied in a single application at the beginning of the growing season. Results showed a significant positive slope in the relationship between P uptake response and mineral P application rate indicating the suitability of the experimental site for P availability assessment. The P bioavailability of Al- and Ca-DPS varied greatly between treatments. The P fertiliser replacement value based on the 1st harvest was 50 and 16% increased to 109 and 31% cumulatively over the four harvests for Al- and Ca-DPS, respectively. The Al concentration in Al-DPS did not limit P bioavailability, but low P bioavailability from Ca-DPS can be associated with its high Ca content that can lead to formation of low soluble Ca-P compounds at alkaline pH conditions with a high Ca/P ratio. These findings show that P availability from dairy sludge can be quite different depending on treatment process. Consequently, it is critical to have P availability information as well as total P content available to ensure the application rate meets crop requirements without creating environmental risk by over application.
", "keywords": ["fertiliser replacement value", "2. Zero hunger", "soil test P", "S", "dairy processing sludge", "phosphorus bioavailability", "Agriculture", "04 agricultural and veterinary sciences", "crop yield", "01 natural sciences", "6. Clean water", "12. Responsible consumption", "Earth and Environmental Sciences", "N use efficiency", "0401 agriculture", " forestry", " and fisheries", "grassland", "0105 earth and related environmental sciences"]}, "links": [{"href": "http://www.mdpi.com/2073-4395/11/3/427/pdf"}, {"href": "https://www.mdpi.com/2073-4395/11/3/427/pdf"}, {"href": "https://doi.org/10.3390/agronomy11030427"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Agronomy", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.3390/agronomy11030427", "name": "item", "description": "10.3390/agronomy11030427", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.3390/agronomy11030427"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2021-02-26T00:00:00Z"}}, {"id": "10.3390/app12010341", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-20T16:19:02Z", "type": "Journal Article", "created": "2021-12-31", "title": "Replacing Mineral Fertilisers for Bio-Based Fertilisers in Potato Growing on Sandy Soil: A Case Study", "description": "The refinement level of bio-based fertilisers (BBFs) can influence environmental and agronomic performance. This study analyses the environmental and agronomic effect of different BBFs on potato growing in sandy soil. A less refined product (liquid fraction of digestate (LFD)), two refined products (ammonium sulphate (AS) and potassium concentrate (KC)), and mineral fertilizer (MF) are compared by conducting: (i) a nitrogen (N) incubation experiment where the N release rate of the BBFs is determined, (ii) a greenhouse gas emission experiment where N2O, CO2, and CH4 emissions after BBF application are measured, (iii) a pot experiment where the nutrient fertiliser replacement value (NFRV) of the BBF is calculated, and (iv) a full-scale field trial where the potato quality and quantity and the remaining N residues in the soil after harvest are assessed. The N release rate and the NFRV of AS (142 \uffc2\uffb1 19% and 1.13, respectively) was higher compared with the LFD (113 \uffc2\uffb1 24% and 1.04) and MF (105 \uffc2\uffb1 16% and 1.00). Lowest N2O emissions were observed after the application of the less refined product (0.02 \uffc2\uffb1 0.01 per 100 g N applied) and highest for MF urea (0.11 \uffc2\uffb1 0.02 per 100 g N applied). In the full-scale field trial, no significant difference in potato yield was observed in the plots that received manure in combination with BBF or MF. This study showed that all three BBFs can safely be used in potato growing on sandy soils. However, the adoption of BBFs can be stimulated by (i) solving the practical issues that occurred during the application of LFD, (ii) making sure BBFs are on the list of RENURE materials so they can legally replace mineral fertiliser, and (iii) reducing the surplus of slurry manure to stimulate the use and fair pricing of BBF products.
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