IWA REGIONAL CONFERENCE OF WATER REUSE AND SALINITY MANAGEMENT http://iwaresa.com/ Soil Fertilization with Human Urine and Salinization Risks 1. Faculty of Engineering, Hokkaido University, Sapporo, Japan., 2 Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo, Japan. 3 Graduate School of Engineering, Hokkaido University, Sapporo, Japan. 4 Faculty of Engineering, Hokkaido University, Sapporo,, Japan. 5 Emeritus Professor, Hokkaido University, Sapporo, Japan 11-15 June 2018, Murcia, Spain Guizani Mokhtar 1,2 , Fujii Takahisa 3 , Hijikata Nowaki 4 , Funamizu Naoyuki 5
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IWA REGIONAL CONFERENCE OF WATER REUSE AND SALINITY MANAGEMENT http://iwaresa.com/
Soil Fertilization with Human Urine and Salinization Risks
1. Faculty of Engineering, Hokkaido University, Sapporo, Japan.,
2 Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo, Japan.
3 Graduate School of Engineering, Hokkaido University, Sapporo, Japan.
4 Faculty of Engineering, Hokkaido University, Sapporo,, Japan.
5 Emeritus Professor, Hokkaido University, Sapporo, Japan
• Countries in Sahel Region (e.g. Burkina Faso), suffers
from low agricultural productivity (low Yield).
• The yield in Sahel region is half of that in Europe
• Causes:
• Lack of water
• No access to machinery
• Infertile soil
• Limited use of fertilizers (due to its high cost)
• Fertilization:
• Sub-Sahara 9kg NPK/ha;
• Elsewhere >100kg NPK/ha
※ Alternative Fertilizers (accessible, Affordable) is required
3
1. Research Background Paper ID:
270
• Human urine is rich in major nutrients nitrogen phosphorus and potassium.
• 7-13g/L-TN; 1g/L-K; 0.2g/L-TP
• Soil fertilization with human urine is an attractive option to recycle
nutrients. (Everyone carry his own fertilizer)
• The average concentration of sodium (Na) in undiluted, fresh human urine:
• 0.94- 0.98 g/L (Kirchmann and Pettersson 1995),
• 2.34 g/L (Pradhan et al. 2010).
• 2.9 - 3.5 g/L Dagerskog and Bonzi (2010).
• Increased Salinization risks (sodication) following the use of human urine as
liquid fertilizer.
7-13g N 0.2g P 1g K
0.8 - 2 L/day
Na ??
※ 24Karat, Home mined Liquid Gold
4
1. Research Background Paper ID:
270
• Burkina Faso is characterized by a rainy
season and dry season.
• Need for Growing Food during the dry
season as well as in the wet season
• Agro sanitation model was proposed
(Ameli-Eaur Project & value chain project)
• Wet Season (grow crops as usual)
• Dry season
─ Recycle grey water for irrigation
─ Apply Urine and feces as a fertilizer
※ Household garden ※ Collection and Storage of urine as a non-conventional fertilizer ※Grey water Treatment
5
2. Research Objectives and Assumptions Paper ID:
270
• Na Salts accumulated on top layers of the soil during dry season cultivation
• Study the removal of Na salts during rainy season
• Effect of washout : How much Na can be removed in rainy season by washout?
• Effect of plant uptake: How much Na can be removed in rainy season by plant uptake?
• Regulation of urine application: How much urine can be applied in dry season?
we assume that salts accumulated in the soil following urine use as a fertilizer can be washed away during the rainy season or absorbed by moderately halophytic plants as a sort of phytoremediation.
Assumptions
Research Objectives
• Sodium Salt accumulation in gardens fertilized with urine
during the dry season (Hijikata et al. 2014).
6
3. Methodology-Exp. pots
• Sorghum planted and non-planted pots, containing an initial
amount of 110mg/pot of sodium in the top layer (the upper
10cm) were irrigated for 8 weeks. The irrigation simulated the
rainy season of a dry climate of Burkina Faso.
• Measurements were performed for leachate volume, Water
content w%, salts concentrations in soil and leachate, EC, pH,
etc…
• A set of pots were broken at each time for subsequent analysis
6 mm/ day of Distilled water
Hoagland solution as nitrogen source 4th day: 230 mg
29th day: 115 mg
The pot experiment assesses the rainy season washout of previously accumulated salts following the assumed urine application as a fertilizer during the cultivation season in planted and non-planted pots.
prior to the salt addition in the upper layer, the soil was saturated with 3 L of de-ionized water to wet the soil for planting.
Experiment setup in the green house of Hokkaido University
7
4. Results and Discussion
Physical and chemical soil characteristics
Daily values of evaporation in planted pots (Obtained from the water balance in the pot experiment)
8
4. Results and Discussion
Total leachate volumes in control and planted pots
0
5
10
15
20
25
1 2 3 4 5 6 7 8
Leac
hea
te (
cm)
Time (Weeks)
Non planted Planted
• Higher leachate was observed in control
pots in comparison with the planted pots
case. This is explained by the fact that the
plant takes up more water after the
development of roots and leaves.
9
4. Results and Discussion
Na leaching in planted and non
planted Pots
Because the initial existing salt contents are
known (22.6 g/m2) and the salts removed by leachate and/or
plant uptake are deduced from experimental measurements,
stored salts in the soil can be obtained.
These findings confirm that evapotranspiration is a predominant factor, and water is removed from soil while salts are left behind. In addition, phytoremediation did not exhibit good results because sorghum is not a good halophyte plant. Therefore, based on these results, salt washout can be expected in bare soils during the rainy season, while sorghum- planted soils will accumulate salt.
0
5
10
15
20
25
30
35
40
2 4 6 8
Na
rem
ova
l am
ou
t (m
g/p
ot)
Time (Weeks)
Plant uptake Leachate
0
20
40
60
80
2 4 6 8
Na
rem
ova
l am
ou
nt
(mg
/Po
t)
Time (Weeks)
Non planted Planted
Plant uptake and leachate of Na in
Planted pots
※Non-planted pot exhibited better Salt washout
𝑈𝐹 =𝐶𝑝𝑙𝑎𝑛𝑡𝐶𝑠𝑜𝑖𝑙
UF: Salt Uptake Factor Naplant: amount of sodium in the plant Nasoil: Amount of Sodium in the soil
𝑈𝐹 =0.6<1
10
3. Methodology- Hydraus-1D simulation
• To further investigate the possibility of full sodium washout from soil, a simulation
using Hydrus 1D software was conducted (ion chemistry UNSATCHEM Module).
• Different conditions were evaluated.
• Evaluation of the effects of different initial Na salts concentration
• Evaluation of Soil amendment with calcium (we assume that peasants in
Burkina Faso can use wood ash which was reported to contain calcium).
pot experiment data are used to calibrate the model. Rainfall data from Burkina Faso,located in sub-Saharan Africa, where used to assess the effect of salt washout during rainy season in both experimental pots and numerical model.
11
3. Methodology- Hydraus-1D simulation
• Model calibration and validation
• Laboratory measurements: soil water retention parameters (Θr and Θs), Soil bulk density.
─ Optimize root mean square error (RMSE) (Water storage, leachate, salt concentration)
─ Retain the values that are in reasonable range
─ Verified to be comparable to values reported in the literature.
• Validation: using another set of data
pot experiment data are used to calibrate the model. Rainfall data from Burkina Faso,located in sub-Saharan Africa, where used to assess the effect of salt washout during rainy season in both experimental pots and numerical model.
12
4. Results and Discussion
Model calibration:
0
5
10
15
20
25
0 2 4 6 8 10
Leac
hat
e V
olu
me
(cm
)
Time (Weeks)
Simulation
Experiemental0
50
100
150
200
250
300
0 14 28 42 56
Na
amo
un
t (m
g/p
ot)
Time (days)
sim exp
a) b)
13
4. Results and Discussion
Na removal During rainy season
Na removal percentage versus Na input
60
70
80
90
100
110
5,5 5,8 6,1 6,4 6,7 7
Na
per
cen
tage
re
mo
val (
%)
Initial Na Input (g/m2)
※ Not all Na salts could be washed out during rainy season
Study period Burkina Faso meteorological conditions
Rainfall (mm)
Evaporation (mm)
July (0-28days) 5.8 4.6
August (29-56days) 7.3 4.4
Amount of Na previously accumulated
14
4. Results and Discussion
※However Full washout is only possible in non planted pots. ※ So, How about soil amendment with Calcium
Component
g/L Total load for 2L
Na 2.84 5.68
T-N 7-13 14-26
7-13g N 0.2g P 1g K
Fujiwara and Narimatsu (2006) : Total nitrogen required to grow Komatsuna: 14 g/m2 (1.07-2L of Urine)
Dry season Na is accumulated in soil
※How much Urine can be applied without Na build up in the soil
Wet season Na is Washout
2 L of Urine will supply the required Nitrogen for plant
(5.68Na load)
Up to 6g/m2 can be fully washout
15
4. Results and Discussion
Soil Na+
Soil
Soil
Na+
Ca2+
• Ca supply in 4th and 29th days, lead to detection of sodium in liquid phase (peaks)
• In the bottom layers, no sodium was detected (desorbed Na, was re-adsorbed in bottom layers)
Amount of Ca to replace Na
16
• This study aimed to investigate the effect of cleaning crop, the rainy season and the soil
amendment with calcium on the fate of salts accumulated from previous cultivations with human
urine.
• We found out that under the climate conditions of Burkina Faso:
• Sustainable cultivation with human urine as fertilizer could be done successfully with proper
application of urine and salt management.
• Although, the non planted pots perform better during rainy season to fully wash out
accumulated salts, the planted pots are favoured to get a harvest.
• In case, of non full washout of sodium, a descent amount of calcium will allow full washout of
sodium
• Our study helps to better understand the best practices in Sahel region to achieve sustainable
cultivation with human urine and promote agro-sanitation.
5. Conclusions
• We conclude that adequate application of urine lead not to salt
accumulation.
• .
IWA REGIONAL CONFERENCE OF WATER REUSE AND SALINITY MANAGEMENT http://iwaresa.com/
• full washout of sodium ions was achieved in non-planted pots only. However, and due to high
evaporation rates, only 20% of the sodium ions were washed out from planted pots. a
Soil water content, leachate and Nitrogen concentration measurements were used to
calibrate the water flow and solute transport processes with no water or osmotic stress
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3. Results and Discussion
Because the initial existing salt contents are
known (22.6 g/m2) and the salts removed by leachate and/or
plant uptake are deduced from experimental measurements,
stored salts in the soil can be obtained.
These findings confirm that evapotranspiration is a predominant factor, and water is removed from soil while salts are left behind. In addition, phytoremediation did not exhibit good results because sorghum is not a good halophyte plant. Therefore, based on these results, salt washout can be expected in bare soils during the rainy season, while sorghum- planted soils will accumulate salt.
Therefore, washout by rainfall may be more efficient than cleanup crops during the rainy season. significant amounts of the applied salts remained in the soil column.