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

• M. Grigatti , L. Cavani, S. Mancarella, L, Sciubba, C. Ciavatta, C. Marzadori

Department of Agricultural Sciences Alma Mater Studiorum – University of Bologna - Italy

Factors affecting the water extractable phosphorus from compost

Cyprus 2016 – 4th International Conference on Sustainable Solid Waste Management - Limassol 23-25 June 2016

Introduction Future P lack

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

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 composting and # of operating composting plants in Italy (Consorzio Italiano Compostatori CIC, 2014). Amount of selected organic waste for anaerobic digestion and # of operating anaerobic digestion plants in Italy (CIC, 2014).

5.500.000 ton of selected organic waste yr-1 25.000 ton P yr-1

Objectives

• Assess the main factors affecting the H2O extractable P in compost beside

to the study of factors affecting the midle-long term releaseble P (NaHCO3 and NaOH) .

• H2O extractable P is recognized to be readily available for plant nutrition;
• NaHCO3 extractable P is recognized to be available in the short-term;
• NaOH extractable P is recognized to be available in the long-term.

Assessment of the different P forms in compost for a better knowledge for rational agronomic re-utilization

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
• f 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 H2O 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):
• H2O; NaHCO3 0.5 M pH 8.5; NaOH 0.1 M; HCl 1M; H2SO4 96%.
• Study of the relationships between those variable and P extractabilty

(Principal component analysis; PCA).

Results

Results Stability (OUR)

10 20 30 40 50 60 70 80 90

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 OUR (mmol O2 kg-1 VS h-1)

Results Total P (aqua regia)

Total P

1 2 3 4 5 6 7 8 9 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 P tot. (mg g-1)

Average P content ( 4.6 mg g-1)

Results Ratios between different P forms in compost

2 4 6 8 10 12 14 16 18 20 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

P (%) PH2O/Ptot

Ratio between H2O extractable and total P in tested compost (PH2O/Ptot)

Results Ratio between different P forms in compost

10 20 30 40 50 60 70 80 90 100 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

P (%) Pi/PH2O (%) Po/PH2O (%)

Ratio between water soluble inorganic P and total P extractable in water (Pi/PH2O) and between water soluble organic P and total P extractable in water (PO/PH2O).

PC 1 (Var. % 28.5%)

• 1,0
• 0,5

0,0 0,5 1,0

PC 2 (Var. % 22.2)

• 1,0
• 0,5

0,0 0,5 1,0

OUR Pi H2SO4 Ca Fe Al pH Pi Po

PC 2 (Var. % 22.2)

• 1,0
• 0,5

0,0 0,5 1,0

PC 3 (Var. % 18.7)

• 1,0
• 0,5

0,0 0,5 1,0

OUR Pi H2SO4 Ca Fe Al pH Pi Po

Results Factors affecting P extractability in water

Stability

Alcalinity

Pi in H2O Po in H2O

Results

Sequential extraction on selected stable compost samples (OUR ≤5 mmol O2 kg-1 VS h-1) as function of PH2O

P speciation

0% 20% 40% 60% 80% 100% 14 18 9 12 Compost P recvrey (P tot (%))

H2SO4 HCl NaOH NaHCO3 H2O

Increasing H2O-P Increasing HCl-P – Ca bound

Readily available Available Available in the midle-term Not-available Residual

CaCO3

Compost

14 18 9 12

CaCO3 (g kg-1)

10 20 30 40 50 60 70

CaCO3 vs H2O-P CaCO3 (g kg-1)

30 35 40 45 50 55 60

H2O P (mg g-1)

0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35

CaCO3 vs NaHCO3-P CaCO3 (g kg-1)

30 35 40 45 50 55 60

NaHCO3-P (mg g-1)

0,4 0,5 0,6 0,7 0,8

CaCO3 vs NaOH-P CaCO3 (g kg-1)

30 35 40 45 50 55 60

NaOH-P (mg g-1)

0,35 0,40 0,45 0,50 0,55 0,60 0,65 0,70 0,75

CaCO3 vs HCl-P CaCO3 (g kg-1)

30 35 40 45 50 55 60

HCl-P (mg g-1)

0,5 1,0 1,5 2,0 2,5 3,0

CaCO3 vs H2SO4-P CaCO3 (g kg-1)

30 35 40 45 50 55 60

H2SO4-P (mg g-1)

0,01 0,02 0,03 0,04 0,05 0,06 0,07

y = -0.008x + 0.5738 R2 = 0.53 y = 0.0108x + 0.0995 R2 = 0.99 y = 0.0693x - 1.4043 R2 = 0.93 y = 0.0018x - 0.0403 R2 = 0.99

Results

Sequential extraction, relationship with total CaCO3 content

Weakly adsorbed Medium-available Stongly adsorbed Not-available

Ryegrass in pot after 21 days of cultivation at 30 mg P kg-1 in calcareous soil.

Results

P apparent recovery fraction (ARF) on Ryegrass

ARF (%)

Days after seeding

15 20 25 30 35 40 45 50

P (recovery % of added P)

5 10 15 20 25 14 18 9 12 P-chem

Relationship H2O-P/ARF (3 weeks)

H2O-P (%)

2 4 6 8 10 12 14

P (recovery % of added P)

4 6 8 10 12 14 16 18 y = 0.8772x + 5.6742; R2 = 0.73

Relationship H2O-P/ARF (6 weeks)

H2O-P (%)

2 4 6 8 10 12 14

P (recovery % of added P)

6 8 10 12 14 16 18 20 22 y = 1.1313x + 6.2273; R2 = 0.74

Relationship NaHCO3-P/ARF (6 weeks)

H2O +NaHCO3-P (%) 16 18 20 22 24 26 28 30

P (recovery % of added P)

6 8 10 12 14 16 18 20 22 y = 1.0872x - 12.028; R2 = 0.64

Results

Relationships between PH2O; P in PNaHCO3 and P uptake by ryegrass

Poor P releaser High P releaser

Discussion

 The 26 composts showed high variability of many traits:

 samples representative of compost production in Italy;  Total P content (Ptot) : variable but very interesting.  Good relationship with CaCO3 and P extractable in:

• H2O (readily available);
• NaHCO3 (available);
• HCl (not available).

 P availability resulted mainly CaCO3 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 (NaHCO3) 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 H2O

Factor loadings (PCA)

Alcalinità-Calcare Maturità-Stabilità Porg in H2O Minore Pi in H2O

P C 1 (V a

• r. 3

9 ,7 % )

• 1

,0

,5 ,0 ,5 1 ,0

PC 2 (Var. 30,3% )

• 1

,0

,5 ,0 ,5 1 ,0 O U R P i P

• rg

C a

Discussion P distributed with compost application 20 ton ha-1

PO4(NH4)2 (150 kg ha-1) 30,1 kg P ha-1 Compost (20 ton ha-1)

Substitution hypotesis (20 ton ha-1)

0,0 10,0 20,0 30,0 40,0 50,0 60,0 14 18 9 12 P (kg ha-1) H2O NaHCO3 NaOH HCl H2SO4

Discussione Fosforo apportato con i diversi compost in un’ipotesi di distribuzione alla dose di 20 ton ha-1

Substitution hypotesis (20 ton ha-1)

2 4 6 8 10 12 14 16 14 18 9 12

P (kg ha-1)

H2O NaHCO3 NaOH

27 kg P ha-1 26 kg P ha-1 25 kg P ha-1 30 kg P ha-1

Fosfato biammonico (150 kg ha-1) 30,1 kg P ha-1 Compost (20 ton ha-1) 25÷30 kg P prontamente e mediamente disponibile ha-1

Variable PC 1 PC 2 PC 3 OUR

• 0.42
• 0.56

Pi H2SO4

• 0.60

0.58 Ca 0.81 Fe 0.84 Al 0.85 pH 0.45 0.47 Pi

• 0.85

Po 0.66 Variance (%) 28.5 22.3 18.7