An assessment of the effect of human faeces and urine on maize production and
water productivity
page 1 / 10
Edward Guzha,
a *
Innocent Nhapi
b
and Johan Rockstrom
c
a
Mvuramanzi Trust, Box MR 103 Marlborough, Harare, Zimbabwe
b
Department of Civil Engineering, University of Zimbabwe, Box MP167, Mt. Pleasant, Harare, Zimbabwe
c
Stockholm Environment Institute, Box 2142, SE 103 14 Stockholm, Sweden
Abstract
The key challenge facing many catchment authorities in Zimbabwe and elsewhere is the challenge of
feeding the growing populations within their catchment boundaries. Modern agricultural practices
continue to mine valuable crop nutrients through increased food production to satisfy ever-increasing
food demand. In recent diagnostic survey of smallholder agricultural sector in the Manyame catchments
of Zimbabwe it was revealed that exhausted soils depleted of their natural mineral and organic
constituents by many years of cropping with little fertilization or manuring were the major factors
contributing to low yields and poor food security in this sector in Zimbabwe. The objective of the study
was to assess the effect of using sanitized human excreta on maize production and water productivity.
The study involved six volunteer farmers with four 10 m x 10 m trial plots each with the following
treatments the control, commercial fertilizer treatment urine only plot, and the feacal matter and urine
plot. .Harvest determination was carried by weighing the yield from each of the treatment plots and
comparisons done .Water productivity was computed by calculating the amount of water used to produce
a tone of maize per ha The study showed that human excreta improves maize crop production and water
productivity in rain-fed agriculture. The study recommends that the ecological sanitation concept and the
reuse of human excreta both humanure and (ecofert) urine can be considered as alternative excreta
management options in catchment areas.
Keywords: Human excreta, humanure, ecofert, water productivity
1. Introduction
The challenge of feeding tomorrow’s world population is largely dependent on improved water
productivity, making optimal use of the available land (Rockstrom, 2003). This could be achieved by
improving soil fertility management by using readily available nutrients from ecological sanitation toilets.
Rain-fed agriculture plays an important role in this respect because 80% of agricultural land world-wide is
under rain-fed agriculture (Rockstrom, 2003). It is anticipated that water productivity enhancement in rain-
fed agriculture could be achieved by integrating nutrient recycling through human excreta use.
Global crop nutrient sources, especially potassium (K) and phosphorus (P), continue to be depleted as
the demand for food to satisfy growing world population increase. It is estimated that the current world
phosphorous reserves will only last for 100 - 150 years (Otterpohl et al., 1996). The known reserves of
currently exploitable phosphate rock are estimated at about 40 billion tons. At the peak rate of
consumption (150 million tons per year) these reserves will last more than 250 years. In addition there
are vast phosphate resources present in the earth crust which, with today’s technology, are not yet
commercially exploitable. Although nitrogen is the earth’s most abundant element (the atmosphere is
78% nitrogen gas) and an essential component of all life, plants can only use nitrogen fixed with
hydrogen and oxygen in the form of inorganic compounds. The current over-exploitation of nitrogen from
the atmosphere in the production of artificial fertilizers is going to upset the nitrogen balance (Gijzen and
Mulder, 2001). . The global fertilizer consumption has generally risen over the past years (Fig. 1) and if
this trend is not reversed soon, will lead to an unsustainable food production situation. It is therefore
Corresponding author.
E-mail address: eguzha@zol.co.zw or eguzha@yahoo.co.uk (E. Guzha)
An assessment of the effect of human faeces and urine on maize production and
water productivity
page 1 / 10
important that humankind aim at efficiently utilizing the available resources so that they would also be
available to future generations. Some schools of thought suggest the use of short, closed cycles in water
and waste management. They argue that the logical path/way of disposing human waste is in agriculture
as this makes use of valuable nutrients, whilst at the same time achieving environmental benefits
associated with excreta disposal into water bodies.
0
20
40
60
80
100
120
61 64 67 70 73 76 79 82 85 88 91 94 97 2000
Year
Fertilizer (kg/ha)
More fertiliser, more food, but more pollution too
0
20
40
60
80
100
120
61 64 67 70 73 76 79 82 85 88 91 94 97 2000
Year
Fertilizer (kg/ha)
0
20
40
60
80
100
120
61 64 67 70 73 76 79 82 85 88 91 94 97 2000
Year
Fertilizer (kg/ha)
More fertiliser, more food, but more pollution too
Fig. 1. Global fertilizer use from 1961 (Source FAO)
The cost of commercial fertilizers cannot be afforded by most poor societies and this is also the sector
that does not have access to cattle manure, thereby forcing these people to do without these fertilizers.
To ensure sustainable food security is achieved through increased food production, it is essential that
cheap and readily available nutrient sources are considered. It is for this reason that ecological
sanitation, ecosan, is now being promoted, offering an alternative to fertilizer with the added benefit of
soil conditioning. In fact, each person is capable of producing enough fertilizer for his food needs (Table
1).
Table 1: Potential for nutrient production from human waste in Zimbabwe
Annual maize needs in Zimbabwe 1,800,000 tonnes
Maize needs per capita/yr for 11,600,000 people in Zimbabwe 155 kg/cap.yr
Assuming 1 ha produces 7 t of maize. 1 ha produces maize for 45 people
Therefore, fertiliser requirements at 175kg/ha per person for N 3.9 kg N/cap.yr
Therefore, fertiliser requirements at 30kg/ha per person for P 0.7 kg N/cap.yr
Compare with sewage
N production at 10 g N/cap.d 3.7 kg N/cap.yr
P production at 2 g P/cap.d 0.7 kg P/cap.yr
An assessment of the effect of human faeces and urine on maize production and
water productivity
page 1 / 10
This paper is based on a study on the potential for utilizing human waste (faeces and urine) for the
production of maize conducted from November 2003 to May 2004 in the Marondera district if Zimbabwe.
The study was based on pilot scale aiming at assessing the potential production based on the yield
(production per unit area) and effect on water productivity (haversted weight per unit volume of water).
2.0 Methodology
2.1. Study area
The study was conducted in the Marondera District Ward 14, in the Chihota Communal Lands (Fig. 2).
The district has a population of 155,000 according to the 2002 national census figures (CSO, 2002). The
soils are predominant wee-drained sand soils which are generally not suitable for intensive crop
production. The water table is shallow at about 3 m. As a result, Mvuramanzi Trust, a locan non-
gvernmental organization, has been promoting the use of ecosan toilets of the Urine Diversion type which
are constructed above-ground type to avoid encountering the water table. The study area falls under
natural region 2 and 3 characterized by average to moderate rainfall ranging between 430mm –
630mm.The rainfall comes around the 15 of October, but is highly variable. Cropping season faces high
rainfall variability with midseason dry extending to as long as three weeks. In some bad seasons the
midseason dry spell causes complete crop failure.
2.2. Experimental setup
The study was designed as a two factor experimental design consisting of 10 m by 10 m randomized
blocks with three (3) repetitions to ensure statistical validity. The major factor investigated was nutrients.
The nutrient factor was assessed on four (4) four levels of treatments consisting of the following:
i. Plot 1: control plot where maize was planted and allowed to grow without any crop nutrients applied.
ii. Plot 2: Normal artificial fertilizer treatments of compound D (NPK 7:18:7) as basal fertilizer treatment
and ammonium nitrate (34.5%) as top dressing were both applied at the rate of 6g per crop, as per
manufacturer’s recommendations.
iii. Plot 3: urine (ecofert) was applied at the rate of 100 ml per crop as the basal treatment and 100 ml as
the top dressing treatment after 4 weeks and when the crop was at knee level, in line with normal
fertilizer application practices in the area.
iv. Plot 4: faecal matter (humanure) was applied as basal fertilizer at the rate of 80 g per planting station,
whilst urine was applied at 100 ml per plant.
The plots were randomly arranged in the sense that no particular treatment had a fixed position in all the
fields. Numbers 1 to 4 were assigned to these treatments as described above for easy computation and
presentation. Plant growth in terms of leaf area stem thickness were monitored at 8 weeks and recorded
for each plot. Measurement of the harvest was done by weighing the maize stalk, the maize cobs and the
maize seed or cereal.
An assessment of the effect of human faeces and urine on maize production and
water productivity
page 1 / 10
Fig. 2. Location map of Marondera District in Zimbabwe
Block A Farmer 1 & 4
Ecofert Control Humanure Commercial
fertilizers
Commercial
fertilizers
Humanure Ecofert Control
Block B Farmer 2 & 5
Control
Ecofert Humanure Commercial
fertilizers
Commercial
fertilizers
Control Ecofert Humanure
Block C Farmer 3 & 6
Commercial
fertilizers
Humanure Ecofert Control
Control Ecofert Humanure Commercial
fertilizers
Block A Farmer 1 & 4
Ecofert Control Humanure Commercial
fertilizers
Ecofert Control Humanure Commercial
fertilizers
EcofertEcofertEcofert ControlControl HumanureHumanureHumanure Commercial
fertilizers
Commercial
fertilizers
Commercial
fertilizers
Commercial
fertilizers
Humanure Ecofert ControlCommercial
fertilizers
Humanure Ecofert ControlCommercial
fertilizers
Commercial
fertilizers
Commercial
fertilizers
HumanureHumanureHumanure EcofertEcofertEcofert ControlControl
Block B Farmer 2 & 5
Control
Ecofert Humanure Commercial
fertilizers
Control Ecofert Humanure Commercial
fertilizers
ControlControl EcofertEcofertEcofert HumanureHumanureHumanure Commercial
fertilizers
Commercial
fertilizers
Commercial
fertilizers
Commercial
fertilizers
Control Ecofert HumanureCommercial
fertilizers
Control Ecofert HumanureCommercial
fertilizers
Commercial
fertilizers
Commercial
fertilizers
ControlControl EcofertEcofertEcofert HumanureHumanureHumanure
Block C Farmer 3 & 6
Commercial
fertilizers
Humanure Ecofert ControlCommercial
fertilizers
Humanure Ecofert ControlCommercial
fertilizers
Commercial
fertilizers
Commercial
fertilizers
HumanureHumanureHumanure EcofertEcofertEcofert ControlControl
Control Ecofert Humanure Commercial
fertilizers
Control Ecofert Humanure Commercial
fertilizers
ControlControl EcofertEcofertEcofert Humanure Humanure Humanure Commercial
fertilizers
Commercial
fertilizers
Commercial
fertilizers
Fig. 3. Layout of the experimental fields used for growing maize with 4 treatments in each case
An assessment of the effect of human faeces and urine on maize production and
water productivity
page 1 / 10
2.3. Determination of water use efficiency
Water use efficiency was determined by adding the total amount of rainfall recorded throughout the
cropping season and calculating the average rainfall using the following formula:
Average Rainfall = Total Precipitation (mm)/ No of rainfall events (1)
Daily rainfall records were made using a “famer’s raingauge”, graduated conical flask type. On the actual
amount of water available to the plant was determined from the following water balance equation:
P = E + T + D + R + δS (2)
Where P = rainfall, mm, determined from rain gauge measurements
E = evaporation, mm,
T = transpiration, mm,
D = drainage, mm,
R is runoff, mm,
δS is change in storage, mm
It was assumed that there would be no runoff considering the daily rainfalls recorded, and the soil
characteristics that affect infiltration and porosity were considered to be the same in all the experimental
plots.
2.4. Determination of water productivity
Equation 2 was used in MS Excel computations to generate water balance and respective water use
efficiencies of different treatments. In the calculation of water productivity, the following collected data
were entered into excel spread sheet treatments: total and average rainfall, supplementary irrigation
(where applicable), average weight of stalk, average weight of cobs and total weight of grain. All the data
was expressed in kgs per hectare. Equation 3 was used to calculate the water productivity.
Wpet = (WP)T/(1-e(by)
5
(3)
Where Wpet = green water productivity (m3ton-1
(WP)T = productive green water productivity m3t-1
1-e)(by)5 = b is a constant and
y = grain yield (t/ha)
(after Rockstrom and Falkenmark, 2000)
The water use efficiency WUE or Wpet parameter is defined in this study as the volume of transpiration
(m
3
) needed to produce 1 ton of dry matter grain yield (m
3
ton
-1
) (WUET).
3. Results and analyses
3.1. Growth monitoring
Plant growth was assessed in terms of plant height, leaf height, and leaf length (Fig. 4).
An assessment of the effect of human faeces and urine on maize production and
water productivity
page 1 / 10
(a) (b)
(c)
Fig. 4 Crop growth analysis based on (a) height, (b) leaf width, and(c) leaf length
A summary of the growth monitoring measurements revealed that humanure + ecofert treated plots had
the tallest crop with the longest leaf length followed by the ecofert only treatment which has the widest
leaf length and the same stem thickness. Growth monitoring graphs (Fig. 4) show that the maize crop
treated with humanure had better plants in terms of height, stem thickness, leaf length and width. One
other distinction was that growth measurement showed that commercial fertilizer treated crops had
longer leaves than all other plots because.
3.2. Maize yield
Maize from different 10 m x 10 m plots were harvested shelled, dried and weighed, with the data
expressed as yield per hectare (kg/ha) (Fig. 5). These results also showed that the ecofert + humanure
treatment was the best followed by ecofert only.
An assessment of the effect of human faeces and urine on maize production and
water productivity
page 1 / 10
Fig. 5 Average grain yields/ha harvested from the four treatments
3.3. Statistical analysis
The statistical analysis of variance treatment effect was analyzed using the Student – Newman Kenls
(SNK) and it showed that yield from humanure + urine (ecofert) treatment (Plot 4) was significantly
larger than the control treatment (1) at p = 0.05) There was no significant statistical difference between
humanure + ecofert treatment and commercial fertilizer or ecofert treatment alone. The study showed
that a much higher yield is obtained if a farmer uses both humanure and ecofert. For example, in the
above figure the harvest from humanure plots is above 3.5 tons/ha and the yield for ecofert treated crop
is slightly above 3 tons/ha. Yield from commercial fertilizer plots is around 2.5 tons/ha and that of the
control is shown to be 1.5 ton/ha. In real practice, however, the yield from a field where no nutrient was
applied could be as bad as zero.
3.4. Water productivity
Figure 6 shows that treatment 4 (humanure + ecofert) used less water per unit weight of maize produced.
This shows that ecosan has a potential to enhance water productivity.
Fig. 6 Water productivity from different treatment sites
An assessment of the effect of human faeces and urine on maize production and
water productivity
page 1 / 10
Water use efficiency ranged from 2,000 – 2,300 m
3
/ton for a non-fertilized crop in the control plot (1).
WUE
et
for crops fertilized with chemical fertilizers compound D and Ammonium Nitrate (2) and ecofert (3)
alone ranged between 1,650 m
3
/ton– 1,700 m
3
/ton. The highest water productivity or efficiencies was
found on plot (4) the crops fertilized by a combination of humanure and ecofert, with WUE
et
of about
1,300 m
3
/ton from different treatments. The study suggests that humanure plus ecofert has the highest
water use efficiency followed by ecofert only, followed by commercial fertilizer. Cultivating without any
nutrient is an inefficient use of scarce water resources.
3.5. Field water balance
Equation 2 was used to compute the water balance. Computation of data was used in order to generate
evapo-transpiration (ET) and drainage (D). Table 2 shows the estimated water balance of the
experimental plots. Using the data from the water balance Table 4.1 above, percentage of water used by
the crop as evapo-transpiration (ET) and the one being lost as drainage (D) was calculated.
Table 2 shows the water balance at the experimental plots the assumption here is that the R is zero
Treatment P (mm) SI (mm) ET (mm) R (mm) D (mm)
C (1) 631 3 411 0 222
CF (2) 631 3 439 0 194
E (3) 631 3 447 0 186
H (4) 631 3 481 0 152
N.B. P is Precipitation, SI is Supplementary Irrigation, ET is Productive Evapotranspiration, R is Runoff,
and D is Drainage
The total water supplied to each experimental plot was calculated and an average worked out. Using the
data from the water balance Table 4.1above, percentage of water used by the crop as evapo-
transpiration (ET) and the one being lost as drainage (D) was calculated. Figure 4.5 below is an attempt
to show the water balance in the control experimental plot.
Figure 7 Water balance in a control plot
The total water supplied to the
humanure plot was calculated
and an average worked out
Using the data from the water
balance table 4.1 above,
percentage of water used by
the crop as evapo-
transpiration (ET) and the one
being lost as drainage (D) was
calculated.
Figure 7 and 8 below shows
the water balance in the
control experimental plot.
An assessment of the effect of human faeces and urine on maize production and
water productivity
page 1 / 10
Figure 8 Water balance humanure + ecofert plots
The above diagrams show the
different water partitioning of
supplementary irrigation (SI) +
rainfall (P) at the experimental
field level. Figure A shows water
partitioning on a field where the
farmer is not applying any form of
nutrient amendment. On such the
study seems to indicate 65% of
the total water supplied is used for
productive evapo-transpiration
(ET) while 35% is lost as
underground drainage (D) and
also to contribute to underground
water recharge.
The second Figure 8 shows a scenario where a farm chooses to embark on a humanure + ecofert maize
production strategy. The study reveals that 76% of the total amount of water supplied to a field is taken
up by plants as total evapo-transpiration (ET) 11% above the water uptake in field where no nutrients
have been used. Consequently a relatively low flow 24% is lost as drainage D. Whilst they is much gain
to the farmer in terms of productive (ET) and corresponding grain yield, they is loss to the underground
water recharge from an (IWRM) perspective
Measurement of harvest from different treatment showed that a combination of humanure and ecofert
assures a farmer of a good return from his capital investment because of good yields. Taking the control
as our base yields increases of about 250% are achieved by using such a combination and increases of
above 200% is achieved by adopting an ecofert only strategy this is still higher than the commercial
fertilizer strategy which gives 166% increases in yields. Statistical analysis of the data using (SNK)
variance of effect analysis tool showed that they was a major statistical difference in harvest between
humanure + ecofert plots compared with the control but they was an insignificant statistical difference
between commercial fertilizer, ecofert and humanure + ecofert confirming the hypothesis that human
excreta works as good if not better that commercial fertilizers. The analyses also indicated that using
humanure + ecofert improves the water productivity in maize production under rain-fed agriculture
considerably.
5.0 Conclusions
Taking into cognisence research limitations such planting dates different farming practices and sample
sizes it can safely be concluded that. Humanure + ecofert improve the water productivity by above 10%
in rain-fed maize production ensuring more crop per drop of water. Water productivity for a crop where
humanure + ecofert is used ranges around 1300 m
3
/ton compared to a situation where nothing was used
which is about 2300 m
3
/ton.
6.0 Recommendations
Governments should revisit legislation and polices that concerns human excreta management and
disposal with a view of defining human excreta as a resource and not a waste. Ecological sanitation
toilets should be added on to the list of approved sanitation systems and technologies in the country so
An assessment of the effect of human faeces and urine on maize production and
water productivity
page 1 / 10
that it becomes an alternative system for people interested in reusing human excreta as fertilizer and also
in areas where it is impossible dig pit to construct Blair latrine
Acknowledgement
The author acknowledges financial assistance from WARFSA/Water Net, Mvuramanzi Trust and
logistical support from Marondera district government extension staff. Finally thanks goes to my late dear
wife Sarah Veronica Guzha and family for enduring my absence during this study.
References
Almaz and Gunda 1998. Ecosan economy and ecological sanitation experiences. SUDEA Addis
Ababa, Ethiopia
Braune and Marks, RF 1983. Appropriate Sanitation Options for Southern Africa. Water Science
Technology Volume 27 University of London UK
Cotton, A and Saywell, D 1998. On Plot Sanitation in Low Income Urban Communities.
Loughborough University UK.
CSO (Central Statistical Office) (2002) Census 2002: Zimbabwe, Preliminary Report, Central Census
Office, Government of Zimbabwe, Harare, Zimbabwe.
Drangert, J.O 1988. Historical overview of sanitation and urine blindness Linkshopping University.
Sweden
Steven Esrey and Ingvar Andersson 1998. Ecological Sanitation Closing the loop to Urban waste
management SIDA Stockholm Sweden
Johansson et al 1997. Reuse of human excreta in crop production paper at Stockholm Water
Symposium 1997 Sweden
Otterpohl, R, Albold, A and Grottker, M (1996) Integrating Sanitation into Natural Cycles: A New
Concept for Cities, in Staudemann, J, Schonborn, A and Etnier, C (Eds.) Recycling the Resource -
Ecological Engineering for Wastewater Treatment, Transtec Publications Ltd, Switzerland.
Rockstrom, J
1
Barron J
2
and Fox, P
2
2003.Water Productivity in Rainfed Agriculture Challenges and
Opportunities for smallholder Farmers in Drought-prone. Tropical Agro ecosystems. UNESCO-IHE
Institute for Water Education, Delft, The Netherlands and Department of Systems Ecology, Stockholm
University, Sweden
Rockstrom, J 2000.Water Resources Management in Smallholder Farms in East and Southern Africa
an overview. RELMA Nairobi Kenya
Rockstrom, J and Malin Falkenmark 2000. Semiarid Crop Production from a Hydrological
perspective: Gap between potential and Actual yields
Rockstrom, J 1999 On Farm Green Water Estimates AS A Tool for Increased Food Production in
water scarce regions The Royal Society
Rockstrom, J 2003 Water for food and nature in drought- prone tropics vapour shift in rainfed
agriculture The Royal Society published on line 18 November 2003.
Morgan, P 1999. Ecological sanitation development a compilation of manuals, Aquamor Pvt. Ltd
Harare.
Shinning, L 2001.The Utilization of human excreta in Chinese agriculture and challenges faced, South
China Agricultural University