1. NUTRIENT USE EFFICIENCY OF LIQUID FRACTION OF DIGESTATE: A THREE – YEAR FIELD TRIAL
Ivona Sigurnjak, C. Vaneeckhaute, E. Michels, B. Ryckaert,
J. Vandenbulcke, G. Ghekiere, F.M.G. Tack, E. Meers

2. OUTLINE
PROBLEM
OBJECTIVES
METHODS
RESULTS
CONCLUSION

3. PROBLEM STATEMENT
Sutton et al. Our Nutrient World: Global overview on nutrient management (2013)

4. OBJECTIVES
Nitrate Directive (91/676/EC) limits manure application up to maximum of 170 kg N/ha
Liquid fraction of digestate (NK-rich)
Solid fraction of digestate (P-rich)
Separation

5. OBJECTIVES Synthetic fertilizer LF of digestate LF of digestate
Nitrate Directive (91/676/EC) limits manure application up to maximum of 170 kg N/ha
Crop N requirements (kg N/ha)
250
Synthetic fertilizer
LF of digestate
LF of digestate
170
Animal manure
Animal manure
Digestate

6. MATERIAL AND METHODS 0,8 ha Location: Wingene, Belgium Area: 0,8 ha
In total 8 scenarios including the reference
n= 4 replicates
32 plots
4 scenarios with LF of digestate
Growing period: April - October
Reference: animal manure + synthetic fertilizers: ammonium nitrate (27% N) and patentkali (30% K2O and 10% MgO)
0,8 ha

7. MATERIAL AND METHODS
Mean nutrient values of animal manure, digestate and LF of digestate in a three-year field trial
Parameters
Animal (pig) manure
Digestate
LF of digestate
DM (%) pH
8.3
EC (mS cm-1) 36 34
Ntot (g kg-1 FW)
NH4-N (g kg-1 FW)
4.5
2.8 – 5.4
P2O5 (g kg-1 FW)
K20 (g kg-1 FW)

8. MATERIAL AND METHODS
Dosage of total N and K2O based on fertilizer analysis and soil advice (225/250 kg N/ha, 80 kg P2O5/ha, 180/250 kg K2O/ha) for the cultivation of maize
Sc.
Years
Mineral Start N
Mineral N
Animal manure
Digestate mixture LF
digestate
K20
P205
kg N/ha
kg K2O/ha
kg P2O5/ha 1
2011 25 29
160 78 80
2012 30
125
213
2013 89 2 18
178
228
225 81 3
140 58 33 77
112
121 76
119
186 4 88

9. MATERIAL AND METHODS
Sampling of plant and soil – July, September, October (harvest), November (nitrate residue)
Physicochemical analysis
PLANT
Yield
Fresh & dry weight, N, P, K, Ca, Mg, Na, S, metals
Biogas potential (2011 and 2012)
SOIL
0-30 cm: dry weight, organic matter, pH-H2O, pH-KCl , EC, N, NO3-N, NH4-N, P, K, Ca, Mg, Na, S, metals, plant available nutrients
30-60 cm, cm: dry weight, organic matter, NO3 -N

10. Fresh weight (FW) biomass yield (t ha-1) in time
RESULTS
Fresh weight (FW) biomass yield (t ha-1) in time
+ SF
- SF

11. Soil NO3-N (kg/ha) residue in time
RESULTS
Soil NO3-N (kg/ha) residue in time
90 kg NO3-N ha-1
+ SF
- SF

12. Nitrogen use efficiency (NUE %) in time
RESULTS
Nitrogen use efficiency (NUE %) in time
+ SF
- SF
- SF

13. Economic and ecological assessment for 2011
RESULTS
Economic and ecological assessment for 2011
Vaneeckhaute, C., et al. Ecological and economic benefits of the application of bio-based mineral fertilizers in modern agriculture. Biomass Bioenergy (2013)

14. CONCLUSION Liquid fraction of digestate in agriculture can:
substitute synthetic NK- fertilizer
result in significant economic and ecological benefits
...however, special attention should be given to its nutrient composition due to high dependence of the input streams in the process of anaerobic co-digestion!

15. THANK YOU FOR THE ATTENTION.
QUESTIONS?
Department of Applied Analytical and Physical Chemistry
Laboratory of Analytical Chemistry and Applied Ecochemistry
Coupure Links 653
B – 9000 Ghent, Belgium
Prof. Dr. ir. Erik Meers
Dr. ir. Evi Michels
M.Sc. Ivona Sigurnjak