soil fertilization with human urine and salinization...

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 Mokhtar1,2, Fujii Takahisa3, Hijikata Nowaki4, Funamizu Naoyuki5

1

Outline of Today’s presentation Paper ID:

…..

1. Research Background

2. Research Objectives and Assumptions

3. Approach and Methodology

4. Results and Discussion

5. Conclusions

2

1. Research Background Paper ID:

270

• 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


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


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).

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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

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Physical and chemical soil characteristics

Daily values of evaporation in planted pots (Obtained from the water balance in the pot experiment)

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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.

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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

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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.

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• Model calibration and validation

• Laboratory measurements: soil water retention parameters (Θr and Θs), Soil bulk density.

• Manual Tuning (hydraulic conductivity K, solute reaction parameters, …)

─ Different initial estimates

─ 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.

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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


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

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※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


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

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• 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/

Thank you!

Mokhtar Guizani

[email protected]

11-15 June 2018, Murcia, Spain

mailto:[email protected]

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• Model calibration and validation

• 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

19


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.

soil fertilization with human urine and salinization...

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