Phosphogypsum from Siilinjärvi plant were tested in soil incubation-leaching-studies(I), and in liquid pig manure treatment (II) in farm pit.



In soil columns, gypsum additions significantly reduced erodibility and ortho-P concentrations in the leaching water.



In the pig manure test, the gypsum-based precipitate fractionated phosphorus to P-rich sediment and to almost P-free upper part. Upper low-P fraction represented 2/3 of the total manure volume

Pietola, Liisa

English

Organic Eprints

www.njf.nuNJF seminar 401 Phosphorus managementin Nordic-Baltic agriculture –reconciling productivityand environmental protectionUppsala, Sweden - 22-23 September 2008NJF Report Volume 4, No 4 • 2008pp _ pNJF Report • Vol 4 • Nr 4 • Year 2008 Gypsum-based management practices to prevent phosphorus transportation     Liisa Pietola  Research Centre Hanninghof, Yara Suomi Oy, Mechelininkatu 1a, PO Box 900, FIN-00181 Helsinki, Finland liisa.pietola@yara.com    Introduction  The phosphorus (P) load on waters caused by field cultivation is one of the most significant environmental problems caused by agriculture. P accumulation into arable soils results from manure use or high P fertilization rates in past decades. In Finland, particularly soil erosion causes significant P load (1-2 kg/ha/a) in spite of considerable decrease (from 30 to 8 kg/ha) in P fertilizer rates from 1990s (SYKE, 2007). Vegetated buffer zones (VBZ) along water courses or constructed wetlands are found to be insufficient to prevent phosphorus losses from fields to waterways. New solutions, tools and products to reduce the P load are required.   Gypsum (CaSO4 .2H2O) as soil amendment inhibits P load: Through Calcium ion (Ca2+) it improves soil structural properties like aggregate stability of clay soil which is important for erosion control. Gypsum also controls P leaching by increasing soil electrical conductivity which improves phosphate binding on soil surfaces (Aura et al., 2006), or through Ca-P precipitation (Zhu & Alva, 1994; Favaretto et al., 2006) in alkaline soils (Kordlaghari & Rowel, 2006). Alternatively, gypsum in liquid manure reduces ortho-P concentration of the liquid phase. This was observed in laboratory with an additional aeration of the manure (Heinonen-Tanski et al., 2000).   Soluble P in soils and manures can be precipitated by Ca, iron (Fe) or aluminium (Al) compounds. Although Fe and Al flocculate soil particles and bind soluble P to Al- and Fe –phosphates in soil solution or liquid manure, this approach is not sustainable as P in Al- or Fe-precipitates are typically unavailable for field crops (at soil pH >3-4). Our approach was to hold P in soil (root zone) as a part of ecological cycle for continuous use in agriculture. This should be achieved by management practices like Ca-precipitation. 78 Material and methods  Phosphogypsum (CaSO4 .2H2O) from Siilinjärvi plant (Yara, former Kemira GrowHow) were tested in soil incubation-leaching –studies (I), and in liquid pig manure treatment (II) in farm pit.   As soil amendment (I), 0-6 g gypsum was mixed to ½ kg soils of different texture, test-P, and pH. Soils were fertilised by soluble phosphates (10-25 mg per soil column) and thereafter watered weekly to field capacity. After 2-3 months, soils were leached with 300 ml water. Molybdate reactive ortho-P concentrations of runoff were measured with (NH4)6Mo7O24.4H2O. The leaching procedure was repeated up to 10 times in order to measure the cumulative P-leaching through soil columns. Similarly, unfertilized soil columns (½ kg soils) of different soil types at different P-status were also treated with 2 g gypsum and cumulative P-leaching, with EC, was measured followed by monthly oversaturation and leaching with 300 ml deionized water. Meanwhile, columns were watered to field capacity each 2 weeks, to attain drying cycles found under natural conditions. Erodibility was analysed by measuring turbidity of the leached waters.    In the manure treatment (II), a farm test was conducted to precipitate the P of pig slurry in farm pit. Gypsum-MgO –based precipitate was stirred into the liquid pig manure, <0.7%. MgO was used for pH rise which was previously observed to be a necessity for the ortho-P decrease. Additionally, MgO provided a building block into struvite (MgNH4-phosphate) precipitation. According to the pre-studies laboratory, no aeration was then needed. After sedimentation, ortho-P concentration and pH of the upper part (liquid) were recorded. Total P of the liquid and the sediment was analysed after 1 and 2 months. The fraction in which the P level was reduced (upper liquid part) represented 2/3 of the total manure volume. Manure samples were taken from different depths to measure the concentrations for total P and K (H2SO4 -HNO3 -soluble), and for water-soluble P, K, NO3-and NH4-N (by photometry TRAACS with Sherwood fl.). Water-soluble P was comparable to ortho-P analysed with (NH4)6Mo7O24.4H2O.  Results and discussion I. Gypsum as soil amendment In soil columns, gypsum additions significantly reduced erodibility and ortho-P concentrations in the leaching water. The effect was clear when agronomic soil test-P (extracted with 0.5 M acid ammonium acetate) was 9 mg/l or more. After 500   79mm rain simulation (10 watering with 300 ml) gypsum rate 6 g/l reduced the ortho-P load from 3.94 to 1.67 g per leached water, when P-fertilization with Ca(H2PO4)2 H2O was 20 mg/l and soil test-P 36 mg/l (Figure 1). Similarly, soil electrical conductivity increased by over 50%. The same phenomenon was recorded for other soil types without P-fertilization (Figure 2). Additionally, gypsum affected particle P as turbidity significantly decreased by 2-g treatment per ½-kg soil (Figure 3).  Currently, gypsum is tested under field and catchment conditions.   938552 510 441 5350500100015002000250030003500400045000 2,1 3,2 4,2 6,3gypsum rate (g/½-kg soil)P  µg / leached water Figure 1. P-leaching from ½ kg soil columns treated with 0-6.3 g gypsum. Numbers represent ortho-P concentration in 1st leaching with 300 ml water. Soil was fertilized with 10 mg P per pot when gypsum was mixed.  020406080100120140160180200P-36 loam P-6 loam P-11 finesandP-9 clay P-13organicP µg/potno gypsumgypsum Figure 2. P-leaching from ½ kg soil columns treated with 2 g gypsum or not. Soils originate from fields of different soil type and P-status. Numbers represent soil test-P (mg/l soil, with acid AAc extraction). The bars represent cumulative ortho-P concentrations after 4 leaching procedure by 300 ml water. Columns were not fertilized.    8001020304050607080P-36 loam P-6 loam P-11 finesandP-9 clay P-13organicNTU no gypsumgypsum Figure 3. Turbidity of leaching waters from soil columns with and without gypsum. See caption of Figure 2 for more details.  II. Gypsum in manure treatment In the pig manure test, the gypsum-based precipitate fractionated phosphorus to P-rich sediment and to almost P-free upper part. Upper low-P fraction represented 2/3 of the total manure volume. In this upper part, total P reduced from 1.05 g kg-1 to 0.13, ortho-P from 0.73 to 0.02g kg-1 (Figure 4).  This P-low part of settled liquid manure is applicable on fields with high soil-P as NK-fertiliser, as liquid phase contained total N 2.1 g kg-1 (ammonium-N 1.9), and total K 1.7 g kg-1. Lower P-rich part contained 3.1 g kg-1 P and 1.3 g ortho-P, respectively. This part could be use as raw material in energy production, or alternatively as P-fertilizer where its use does not induce P leaching or transportation from fields. N-concentration in the "solid phase" (DM 18%) was 3.6 g kg-1 (ammonium-N 1.9). K concentration was 2.0 g kg-1 in the solid fraction, but water soluble K remain same (1.8) both in liquid and solid fractions.  Currently, the method is optimised for cattle slurry.   010020030040050060070080014.5.07 16.5.07 18.5.07 20.5.07 22.5.07 24.5.07 26.5.07 28.5.07 30.5.07 1.6.07P mg/kg Figure 4. Ortho-P concentration of flowing pig slurry above settled fraction, after gypsum treatment with additives like MgO.     81References Aura, E., Saarela, K., Räty, M., 2006. Savimaiden eroosio. MTT:n selvityksiä 118. http://www.mtt.fi/mtts/pdf/mtts118.pdf Favaretto, N., Norton, L.D., Joern, B.C., Brouder, S.M., 2006. Gypsum amendment and exchangeable calcium and magnesium affecting phosphorus and nitrogen in runoff. Soil Sci. Soc. Am. J. 70, 1788-1796.  Heinonen-Tanski, H., Hirvonen, A., Tanni, K., 2000. Phosphorus loads caused by slurry fertlization to waters may be reduced by slurry aeration and waste gypsum powder. Pro Terra 4, 106-107. Kordlaghari, M.P., Rowell, D.L., 2006. The role of gypsum in the reactions of phosphate with soils. Geoderma 132, 105-115. SYKE, 2007. Vesiensuojelun suuntaviivat vuoteen 2015. Riktlinjer för vattenskydd fram til år 2015. Suomen ympäristö 10.  http:// www.ymparisto.fi/download.asp?contentid=66351&lan=fi Zhu, B., Alva, A.K., 1994. The effect of gypsum amen dement on transport of phosphorus in a sandy soil. Water Air Soil Poll. 78, 375-382.      82

Gypsum-based management practices to prevent phosphorus transportation

Significant agricultural P load decrease on waters is observed. Practical methods to achieve the load decrease is developed; provide solutions for farmers, are included into the Finnish agri-environmental support scheme. Practical methods includes: gypsum as soil amendment for erosion and soluble P control, gypsum-based precipitate in manure treatment to fractionate P

Gypsum-based management practises to prevent phosphorus transportationLiisa PietolaResearch Centre Hanninghof, YaraYara Suomi Mechelininkatu 1aPO Box 900FIN-00181 HelsinkiNJF seminar 401 on “Phosphorus management in Nordic-Baltic agriculture – reconciling productivity and environmental protection”  22-23.9.2008Liisa Pietola 22 Sep 2008Contents1. Background 2. Introduction to the principles  Gypsum as soil amendment Gypsum-based precipitate in manure treatment3. Testing principles: preliminary studies 2006-20074. Testing principles in full scale 2008-20105. ConclusionsLiisa Pietola 22 Sep 2008 The eutrophication of the Baltic Sea is severe: many efforts are currently underway to improve the situation. – the phosphorus transportation from agricultural soils should be strongly limited Hot spots for P losses from agriculture  Erodible clayed fields:– With slopes– Without slopes – during snow-melt period and rains – soil particles escape fields transporting P to waters  Fields with high soil test P: – Fields used for sugar beets, vegetables etc. (non-grains)  – Fields where manure has been spread for years on N content basis– P surplus in manure use:  Pig manure P:N 1:3 vs. cereals 1:6 or grasses 1:9 1. BackgroundLiisa Pietola 22 Sep 2008Farmers need specific tools to control P losses in addition to best management practises like drainage and liming  Reduced tillage – direct sowing  Constructed wetlands   Buffer zones + Chemical methods – P absorption – In-field – not out– For crop reuse – no too strong precipitation mechanismsOur targets1. Background Liisa Pietola 22 Sep 2008Kuva: Asko Kinnunen- Approach to keep P in soil (root zone) as a part of ecological cycle for continuous use in agriculture by addition of Ca-based amendments - Focus on gypsum –based products for environment tools in farming with two main applications:  1. Gypsum as soil amendment enhancing phosphorus trapping- by erosion / particle P –control via improved soil aggregation- by P leaching control via enhanced adsorption on particle surfaces2. Gypsum in liquid manure treatment for phosphorus fractioning - P-free effluent after solid removal and settling of phosphates  - P-rich solids at the bottom of farm pitI Soil application II Manure application2. Introduction to the principles Liisa Pietola 22 Sep 2008 CaSO4 . 2H2O is by-product produced by wet process phosphoric acidby the reaction of phosphate rock with sulphuric acid Originates from Siilinjärvi phosphate rock Figs: Asko KinnunenBoth tools base on utilization of Siilinjärvi phosphogypsumLiisa Pietola 22 Sep 20085. For NPK-fertilizer or energy production4. For NK-fertilizer use1. Precipitate powder/fine granules2. Stirring 3. Sedimentation by settling PRINCIPLE 1. Liquid Manure treatment - P fractioning on focus Precipitate (0,2-0,5 %)Ca-phosphatesMgNH4-phosphateP available for cropsno / low Phigh PLiisa Pietola 22 Sep 2008Fig: S. AlasuutariTesting principlews P concentration in upper part  of the manure Ortho-P (mg/kg) in liquid phase:14 May 20 May 30 MaypH 8.4Sampled from 0-10 cm, May 21 and 30 also from 30 cm (no differences between depths) Liisa Pietola 22 Sep 2008(unlike Al- or Fe-phosphates)* Ca-phosphatesMgNH4-phosphateP available for crops100 m3P-tot 105 kgP-ws 73 kg PrecipitatePowder at ~5 kg/tnP-tot 5 kgP-ws  2 kgDM 2%pH 8.5 100 m320-30 m3P-tot 100 kgP-ws 40 kg P-free effluent after solid removal by settling = NK fertilizer P-rich solids* = P-fertilizer/for energy70-80 m3P-tot 5 kgP-ws 2 kgP1 big bag gypsum-based –precipitate is mixed into the slurry container (90 m3)Testing principle 2006-07: Application with liquid pig manure (at 15-20 degrees C, after 1-2 days)Liisa Pietola 22 Sep 2008 By controlling P transportation through runoff / erosion: typically particle P or drainage water: typically soluble P Aiming to keep P usable for crops:  Chemical treatment on Ca-based compounds Ca-sulphate dissolves readily and  – Increases soil Ca and EC– Which enable P trapping   PRINCIPLE 2. Soil treatment-P trapping into soils on focusFig: Asko KinnunenP in leaching water by in mass flow:decreases by increased ECPO43-P in particles in runoff: decreases by aggregationby increased CaLiisa Pietola 22 Sep 2008Kipsimuhitus 2_06: Fosforin huuhtoutuminen938552 510 441 535575271 209 212240479224146 182171433175154 128144354183133 12813727315199 919320414399 9579270182110 897221116794494320613811793910500100015002000250030003500400045000 2,1 3,2 4,2 6,3P  µg63d56d49d42d35d28d21d14 d7 d1dEach ”box” represents ws P / 300 ml watering which was percolated through soilsEC ~ 0.2 µS/mmGypsum g / ½ l soilLoamy soil, test P 6 mg/l; pH 6,9; EC 0.1 (P-fertilization 10 mg/l)Testing principle 2008:Laboratory results from incubation-leaching testsLiisa Pietola 22 Sep 2008Turbidity 24.1.200801020304050607080P-36 loam P-6 loam P-11 finesandP-9 clay P-13organicNTUno gypsumgypsumP (µg/pot) 24.1.2008050100150200P-36 loam P-6 loam P-11 finesandP-9 clay P-13organicP µg/potno gypsumgypsumNumbers represent  soil test-P (mg/l soil, with acid AAc extraction)Phosphorus in percolated water from gypsum treated(4 g  per soil litre) soil columns, control (no gypsum) (n=3)= Ws-P=TOT-PTesting principle 2007-08:Laboratory results for different soilsafter 5 months incubation with wetting-drying cycles, no P fertilizationLiisa Pietola 22 Sep 20084. Testing principles in full scale 2008-2010 by TraP project / Yara’s environmental research on water qualityIn-field P trapping= “TraP and Recycle”Liisa Pietola 22 Sep 2008TraP - Novel gypsum-based products for farm scale phosphorus trapping Under farm conditions &  at catchment scale  With Finish Funding Agency for Technology (Tekes) – support Yara coordinates and purchases research from partners – SYKE Finnish Environment Institute – MTT Agrifood Research Finland – Plant production – Economics – TTS Work Efficiency Institute – Luode Consulting Ltd.  Yara focus on R&D on product recipes, quality control, manufacturing and logistics: In co-operation with other partners:   Water Protection Association of The River Vantaa and Helsinki region Uusimaa Environment Centre, local farmers Liisa Pietola 22 Sep 2008Conclusions / Project missionSignificant agricultural P load decrease on waters is observed 1. In accordance with the goals set by the Government of Finland in national water protection policy2. HELCOM& Practical methods to achieve the load decrease is developed1. Provide solutions for farmers – to be used in hot spots of P-loading:  – erodible soils – high P status soils;by better manure management2. Are included into the Finnish agri-environmental support schemePractical methods includes:  Gypsum as soil amendment for erosion and soluble P control Gypsum-based precipitate in manure treatment to fractionate PLiisa Pietola 22 Sep 2008

Gypsum-based management practices to prevent phosphorus transportation

Abstract

Similar works

Full text

Available Versions

Organic Eprints

Organic Eprints