Factors affecting the water extractable phosphorus from compost M. - PowerPoint PPT Presentation

Factors affecting the water extractable phosphorus from compost M. Grigatti , L. Cavani, S. Mancarella, L, Sciubba, C. Ciavatta, C. Marzadori Department of Agricultural Sciences Alma Mater Studiorum – University of Bologna - Italy Cyprus 2016 – 4 th International Conference on Sustainable Solid Waste Management - Limassol 23-25 June 2016

Introduction Future P lack 20 Mt/yr Phosphate rock are utilized to produce P fertilizers, (Cordell et al., 2009) “Phosphorus Peak” (Jasinski, 2006; EFMA, 2000)

Introduction Future P lack Volatilità dei prezzi della roccia fosfatica e dei fertilizzanti. Spotted production High risk for purchasing Not for selling

Introduction P cycle in the food and non-food crop production (Cordell et al., 2009) P total production (Mt y -1 ) P in Compost & Digestates 1 Mt y -1

Introduction Compost as possible P source Amount of Selected Organic Waste for Amount of selected organic waste for composting and anaerobic digestion and # of operating # of operating composting plants in Italy anaerobic digestion plants in Italy (Consorzio Italiano Compostatori (CIC, 2014). CIC, 2014).  5.500.000 ton of selected organic waste yr -1  25.000 ton P yr -1

Objectives Assessment of the different P forms in compost for a better knowledge for rational agronomic re-utilization  H 2 O extractable P is recognized to be readily available for plant nutrition;  NaHCO 3 extractable P is recognized to be available in the short-term;  NaOH extractable P is recognized to be available in the long-term.  Assess the main factors affecting the H 2 O extractable P in compost beside to the study of factors affecting the midle-long term releaseble P (NaHCO 3 and NaOH) .

Materials & Method Compost samples 26 compost samples from the northern-center Italy:  Selected organic fraction of municipal solid waste with tree pruning;  Anaerobic digestate from the selected organic fraction of MSW with tree pruning (wet and dry-batch digestion);  Green waste (tree pruning).

Materials & Method  Assessment of the main physical chemical traits:  pH, TS, VS, C, N, C/N;  Stability: (Oxygen Uptake Rate);  Total P content and other elements: Ca, Fe, Al, Mn, Mg;  Assessment of the H 2 O estractable P:  300 mg of sample in 30 ml H2O (2h, 25 ° C), centrifugation, filtration;  Total P via ICP;  Inorganic P via Murphy and Riley method;  Organic P = Total P - Inorganic P.  Sequential extraction (on selected stable compost):  H 2 O; NaHCO 3 0.5 M pH 8.5; NaOH 0.1 M; HCl 1M; H 2 SO 4 96%.  Study of the relationships between those variable and P extractabilty (Principal component analysis; PCA).

Results

Results Stability (OUR) 90 OUR (mmol O 2 kg -1 VS h -1 ) 80 70 60 50 40 30 20 10 0 14 13 11 18 9 17 19 12 10 7 20 23 25 21 8 26 2 15 4 22 16 6 5 3 24 1 Compost

Results Total P (aqua regia) Total P 9 8 Average P content 7 P tot. (mg g -1 ) ( 4.6 mg g -1 ) 6 5 4 3 2 1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Compost

Results Ratios between different P forms in compost PH2O/Ptot 20 18 16 14 12 P (%) 10 8 6 4 2 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Ratio between H 2 O extractable and total P in tested compost ( P H2O /P tot )

Results Ratio between different P forms in compost Pi/PH2O (%) Po/PH2O (%) 100 90 80 70 60 P (%) 50 40 30 20 10 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Ratio between water soluble inorganic P and total P extractable in water ( P i / P H2O ) and between water soluble organic P and total P extractable in water ( P O / P H2O ).

Results Factors affecting P extractability in water 1,0 1,0 Ca Po Pi H2SO4 0,5 0,5 pH PC 2 (Var. % 22.2) pH PC 3 (Var. % 18.7) Pi in H 2 O Al Po Fe Alcalinity Pi 0,0 0,0 Pi H2SO4 Fe Al OUR Ca -0,5 -0,5 OUR Pi -1,0 -1,0 -1,0 -0,5 0,0 0,5 1,0 -1,0 -0,5 0,0 0,5 1,0 PC 1 (Var. % 28.5%) PC 2 (Var. % 22.2) Stability Po in H 2 O

Results Sequential extraction on selected stable compost samples (OUR ≤5 mmol O 2 kg -1 VS h -1 ) as function of P H2O Increasing HCl-P – Ca bound P speciation 100% 80% Residual P recvrey (P tot (%)) H2SO4 Not-available 60% HCl NaOH Available in the midle-term 40% NaHCO3 Available H2O Readily 20% available 0% 14 18 9 12 Compost Increasing H 2 O-P

Results Sequential extraction, relationship with total CaCO 3 content CaCO 3 CaCO 3 vs H 2 O-P CaCO 3 vs NaHCO 3 -P 70 0,35 0,8 y = 0.0108x + 0.0995 R 2 = 0.99 60 0,30 NaHCO 3 -P (mg g -1 ) 0,7 CaCO 3 (g kg -1 ) 50 0,25 H 2 O P (mg g -1 ) 40 0,20 0,6 30 0,15 20 0,10 0,5 Weakly adsorbed y = -0.008x + 0.5738 10 0,05 R 2 = 0.53 Medium-available 0 0,00 0,4 14 18 9 12 30 35 40 45 50 55 60 30 35 40 45 50 55 60 CaCO 3 (g kg -1 ) CaCO 3 (g kg -1 ) Compost CaCO 3 vs NaOH-P CaCO 3 vs HCl-P CaCO 3 vs H 2 SO 4 -P 0,75 3,0 0,07 y = 0.0018x - 0.0403 y = 0.0693x - 1.4043 0,70 R 2 = 0.93 R2 = 0.99 0,06 2,5 0,65 H 2 SO 4 -P (mg g -1 ) NaOH-P (mg g -1 ) HCl-P (mg g -1 ) 0,05 0,60 2,0 0,55 0,04 1,5 0,50 0,03 0,45 1,0 0,02 0,40 Stongly adsorbed 0,35 0,5 0,01 30 35 40 45 50 55 60 30 35 40 45 50 55 60 30 35 40 45 50 55 60 Not-available CaCO 3 (g kg -1 ) CaCO 3 (g kg -1 ) CaCO 3 (g kg -1 )

Results P apparent recovery fraction (ARF) on Ryegrass Ryegrass in pot after 21 days of cultivation at 30 mg P kg -1 in calcareous soil.

Results Relationships between P H2O ; P in P NaHCO3 and P uptake by ryegrass Relationship H 2 O-P/ARF (3 weeks) ARF (%) High P 25 18 releaser 16 P (recovery % of added P) P (recovery % of added P) 20 14 14 18 15 12 9 12 10 P-chem 10 8 5 6 y = 0.8772x + 5.6742; R 2 = 0.73 0 4 Poor P 15 20 25 30 35 40 45 50 0 2 4 6 8 10 12 14 Days after seeding H2O-P (%) releaser Relationship H 2 O-P /ARF (6 weeks) Relationship NaHCO3 -P/ARF (6 weeks) 22 22 y = 1.1313x + 6.2273; y = 1.0872x - 12.028; R 2 = 0.64 R 2 = 0.74 20 20 P (recovery % of added P) P (recovery % of added P) 18 18 16 16 14 14 12 12 10 10 8 8 6 6 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 H2O-P (%) H 2 O +NaHCO3-P (%)

Discussion  The 26 composts showed high variability of many traits:  samples representative of compost production in Italy;  Total P content ( P tot ) : variable but very interesting.  Good relationship with CaCO 3 and P extractable in:  H 2 O (readily available);  NaHCO 3 (available);  HCl (not available).  P availability resulted mainly CaCO 3 driven in tested stable compost.

Conclusion  During the composting process the mineralized P-org precipitate with Ca, thus reducing plant available P;  The study of (free) water soluble P beside to the labile Ca- bound (NaHCO 3 ) can reliable predict plant-available P from compost.  (Stable) Compost utilization can ensure interesting amount of plant-available P this beside to the organic matter restoration, especially in mediterannean region (calcareous soils).  Longer pot trial are now running to assess the role of metal-bound P (NaOH-P).

Thank you for your attention marco.grigatti@gmail.com

Results Fattori influenti la estraibilità del P in H 2 O Factor loadings (PCA) 1 ,0 0 ,5 Porg in H 2 O Maturità - Stabilità P i ) 2 (Var. 30,3% 0 ,0 PC C a -0 ,5 O U R P o rg -1 ,0 -1 ,0 -0 ,5 0 ,0 0 ,5 1 ,0 P C 1 (V a r. 3 9 ,7 % ) Alcalinità -Calcare Minore P i in H 2 O

Discussion P distributed with compost application 20 ton ha -1 PO 4 (NH 4 ) 2 (150 kg ha -1 ) Compost (20 ton ha -1 ) 30,1 kg P ha -1 Substitution hypotesis (20 ton ha -1 ) 60,0 50,0 40,0 H2O P (kg ha -1 ) NaHCO3 30,0 NaOH HCl H2SO4 20,0 10,0 0,0 14 18 9 12

Discussione Fosforo apportato con i diversi compost in un’ipotesi di distribuzione alla dose di 20 ton ha -1 Compost (20 ton ha -1 ) Fosfato biammonico (150 kg ha -1 ) 25 ÷ 30 kg P prontamente e 30,1 kg P ha -1 mediamente disponibile ha -1 Substitution hypotesis (20 ton ha-1) 16 30 kg P ha -1 27 kg P ha-1 26 kg P ha-1 25 kg P ha-1 14 12 10 P (kg ha -1 ) H2O 8 NaHCO3 NaOH 6 4 2 0 14 18 9 12

PC 3 Variable PC 1 PC 2 -0.56 -0.42 OUR 0.58 P i H2SO4 -0.60 Ca 0.81 Fe 0.84 Al 0.85 0.47 0.45 pH P i -0.85 0.66 P o 18.7 Variance (%) 28.5 22.3