Experiments
using urine and humus derived from ecological toilets
as a source of
nutrients
for growing
crops.
Peter Morgan
2003
Experiments using urine
and humus derived from ecological toilets
as a source of nutrients for growing crops.
Peter Morgan
The need to improve
home-based agriculture, in a world which lacks sufficient food and where top
soils are often leached out and infertile is a pressing challenge - but where
will the nutrients and humus come from? Commercial fertilizers are beyond the
means for huge numbers of people who grow food in their own back yards, and
animal manures may also be out of reach for those living in the peri-urban
fringe. Home made compost is one realistic possibility, and the great wealth of
nutrients known to be present in human excreta, another. Perhaps the best is
when compost and processed human excreta are mixed and added to the soil.
Currently however, most human excreta is completely lost to agriculture.
It finds its way into deep pit latrines
or into sewer pipes or septic tanks – and has little chance to add new life and
vitality to the topsoil where plants grow.
Fortunately the
world of ecological sanitation is rising to meet this immense global challenge,
where the nutrients available in human excreta, representing a huge and as yet
almost untapped source of “plant food,” are processed in such a way that they
can have enormous potential to benefit agriculture and food production.
Those who believe in
permaculture and organic farming are well aware that plants enjoy growing in a
living fertile soil and not one that lacks life and is just fed nutrients
alone. Fortunately human faeces can change into a remarkably fertile humus,
which can act as an excellent soil conditioner, improving the texture as well
as nutrient levels held in the soil. The urine itself is known to be filled
with nutrients useful for plant growth. But even the use of urine requires that
the soil contains humus, if the nutrients it contains are to be released in a
form which the plant can use for growth. If we are serious about utilising the
precious nutrients which arise from human excreta in agriculture, we must also
take into account the nature of the soil itself. Thus in forming links between
ecological sanitation and improved food production, good agriculture practice
and a culture of soil improvement must be encouraged.
Most eco-toilets used
throughout the world today employ the concept of urine diversion, where the
urine and faeces are separated and processed independently, making them easier
to process. Popular and successful as this method is, it is by no means the
only method of effectively recycling the nutrients held in our excreta. In a
revival of a traditional technique used for generations in many countries in Africa
and elsewhere, the ancient concept of planting trees in decomposing excreta
held in pit latrines is once again becoming more popular. This simple yet
elegant technique is now accepted as belonging to a family of alternative ways
of recycling nutrients held in human excreta and has enormous potential for the
future, especially in poor developing countries.
Recycling nutrients by growing trees in shallow pits - the Arborloo method.
The Arborloo refers to a
simple, low cost, shallow pit toilet where the toilet slab and structure are
portable and move from one pit site to the next at about one yearly intervals.
Thus a new, shallow, (0.6m – 1m deep) pit is dug every year. Once nearly full,
the used pit is topped up with soil and a young tree is planted and protected.
Sounds all too simple, and yet it is a most effective way of recycling the
nutrients held in human excreta. The tree roots invade the organic material
once converted into humus and take up the nutrients and convert them into
vegetative growth and fruit.
Under suitable planting conditions most trees can grow well on latrine
pits
Vigorous banana growth on Arborloo
pit in Zimbabwe
The Arborloo method differs
somewhat from the more traditional method of planting trees in old abandoned deeper
pit latrines. With the Arborloo, both soil and wood ash are
regularly added to the pit contents during the year of use. These additional
ingredients hasten the production of humus and prepare a “pit soil” which is
very suitable for tree growth and more so that composted raw excreta alone.
Also the pits are dug deliberately shallow, which makes them easy to excavate
for the family, but perhaps more importantly, also distances them more from the
underground water table, thus reducing the risks of underground water
contamination. In addition, the more rapid formation of humus in shallow pits
which have a mix of ingredients may also reduce the potential risks of
pathogens contaminating underground water. The composting process is aerobic,
and not so anaerobic as in the deep pit latrines, where excreta may remain
unchanged for years, especially in the deeper zones. So, to put it simply, trees have an easier time of penetrating
shallow Arborloo pits with their humus and can utilise most of
the nutrients which become available. The young trees are planted in a layer of
soil about 10cm – 15cm deep placed above the pit contents. Trees die if they
are planted directly in excreta.
The Arborloo is a portable
toilet structure placed over a shallow pit. It moves on a “never ending
journey” through the lands, a tree being planted in soil placed over the pit
contents. This example comes from Malawi, where arborloo’s are very popular
(Photo: Jim McGill)
Obviously this
technique is most suited to places where there is space to plant a tree. The
method is becoming very popular in countries like Mozambique, Malawi, Zambia,
Kenya and Zimbabwe, and is being tested in South Africa. Its low cost and
forgiving nature and the fact that the excreta is never touched by human hand
are seen as important features. The growth of a new tree every year, which can
turn into fruit orchards or wood lots is seen in a very positive light by the
users. There are reports from a number
of countries of the fruits being larger and the trees altogether more healthy
than similar trees planted nearby in the topsoil.
Another important feature is
that this method is, in essence, a revival of an established concept. Mbachi
Msomphora (pers.comm. 2001) reports of the frequent planting of banana trees on
old latrine pits in Malawi. She also reported of the Cham’mwamba tree (Moringa oliefera) and Mtumbu tree (Kirkia
acuminata) being planted on abandoned full pit latrines in Malawi. The
practice is also quite widespread in Africa (Rwanda , Kenya, Mozambique,
Malawi, Zambia and even Zimbabwe). It was used by the Pilgrim Fathers when they
arrived in the New World (Steve Esrey. pers. comm. 2001) The fact that it is so
widely practiced means that it is logical and acceptable from the users point
of view.
Nutrient levels in Arborloo
soil
Analysis of Arborloo
pit soil shows significantly elevated levels of all the major nutrients
required for good plant growth, compared to normal topsoil, as the table below
shows. In this case Arborloo pit soil was a combination of faeces, urine and poor
topsoil only, revealing the high source of all the major plant nutrients
derived from the excreta alone.
Analysis of Arborloo pit soil
compared to a mean of various topsoils
Soil source pH N* P* K* Ca* Mg*
Local topsoils
(mean of 9 samples) 5.5 38 44 0.49 8.05 3.58
Arborloo (one yr. after tree planting. N=2) 5.95 111 309.5 0.95 11.07 5.1
*Nitrogen
(N*) and Phosphorus (P*) are expressed as ppm and Potassium (K*), Calcium (Ca*)
and
Magnesium (Mg*) as ME/100gms.
The initial growth of tree
roots takes place within the 0.6 cu.m. of this enriched soil formed each year,
and normally ensures healthy root growth for the future tree. This may be due
to the high levels of phosphorus present in the pit soil, a nutrient well supplied
from human faeces. Tree root invasion of the organic soil may be slow at first,
depending on the rate of humus formation, but inevitably tree growth becomes
rapid. This process may take up to two years depending on the soil/excreta mix
and the type of tree and level of watering and protection. Trees vary in their
reaction to the humus and the proportion of soil to human excreta will also
vary from one pit the other. The higher the soil content, the faster the
conversion of excreta to humus. The inclusion of wood ash provides more potash
and addition of leaves also improved the final texture and elevates nutrient
levels of the processed “pit soil.”
Evidence of enhanced tree growth.
Quantitative evidence of
enhanced fruit production in trees planted on Arborloo pits is not yet
available, although there are numerous visual reports of healthy trees and
vigorous fruit growth from many countries. Fruit trees like banana, mango,
guava, mulberry, avocado, paw paw and several citrus species respond positively
to the organic pit environment, provided they are planted in topsoil and not in
the excreta itself. A wide variety of
indigenous trees also respond positively including such species as Brachystegia
glaucescens (mountain acacia), Acacia abbyssinica (African thorn
bush), Albizia gummifera
(peacock flower) and Swartzia madagascariensis (snake bean tree). In Malawi the indigenous tree Kirkia
acuminata, and the exotic and valuable “Moringa tree” (Moringa oliefera),
are traditionally planted on old latrine pits (Mbachi Msomphora
pers.comm.) In Kenya the “Neem” tree (Azadirachta
indica) which has so many valuable properties also grows well in this
organic environment (Obiero Ong’ ang’a pers.comm.). The eucalyptus species also
grow rampantly in this medium as well as many other tree species (see Vol. III
of Ecological Sanitation by PRM).
A young tree has been planted in an Arborloo
pit in Malawi
(photo: Jim McGill)
Citrus tree growing on Arborloo pit
in Kenya
The Arborloo, is the simplest
and cheapest eco-toilet system used within the technical range of systems
possible under the eco-san umbrella. Because of its ease of use and maintenance
it is ideal as an entry point into the world of eco-sanitation, and one of the
best examples of “closing the loop.” But perhaps the most important aspect of
this concept is its link to the tree. The world lacks trees and they have such
a beauty and value of their own which adds to the world we live in. There is no
part of the world that would not benefit by having more trees. The tree is one
of Nature’s marvels. It can be the provider of food, fuel, building materials
and medicine. It helps to stabilise the soil and offers shade. It provides leaf
litter and thus provides additional fertility to the soil, It also provides
beauty and richness to our environment.
Recycling nutrients by making humus in shallow pits – the Fossa alterna method.
In many ways this system,
which also composts excreta in shallow pits, works like the Arborloo.
The twin pits used in this system are shallow, usually about 1.2 metres deep
and placed between 0.5m and one metre apart. Like the Arborloo, a combination
of soil, wood ash and if possible, leaves, are added to the shallow pit in
combination with urine, faeces and anal cleansing material. Unlike many double
vault pit systems, only a single
latrine slab is used and this alternates every year from one pit to the other
and then back again. The challenge of the Fossa alterna, as this system is
called, is to induce the
rapid conversion of excreta into a safe and workable humus within the time it
takes to fill the second pit with excreta and soil/ash. This would not be
possible in the normal pit latrine, where only excreta are added. But where
soil and ash are added regularly, and in sufficient quantity, the whole process
of humus formation is accelerated. In small to medium sized families, (around 6
persons) humus is formed in well drained pits well within the filling time of
the second pit. This being the case, it therefore becomes possible to alternate
the use of the pit on a yearly basis. This effectively makes the system
permanent, because every year a pit of valuable humus is formed, and is easily
excavated, thus making available an empty pit for the next year’s use. This
method has been particularly successful in Mozambique under a programme
supported by WaterAid. In this programme the portable slab and twin pits are
used within a single permanent superstructure.
Every year approximately 600 litres of fertile humus is formed in the
composted pit and this can be used on vegetable gardens. Where the toilets are
used by more people, the pits are dug deeper
- to 1.5 metres (Ned Breslin. pers. comm.) or a third shallow pit can be
introduced.
In the Fossa alterna the use of the toilet
alternates at 12 month intervals between two
shallow pits,
which are protected with a ring beam or brickwork at the pit head. Soil and ash
are added regularly to the pit contents, which helps to convert the excreta
into humus.
Fossa alterna in an urban suburb of Harare
Interior of the Fossa alterna.
The bucket contains a mixture of dry soil and wood ash (4:1)
The Fossa alterna does not
occupy much space and if correctly managed
provides many years of trouble free service and fertile humus every year
Fossa alterna in WaterAid’s successful programme in Niassa
Province in Mozambique.
Here the structure is not portable, as in the Zimbabwe examples. The two
shallow pits are placed within the structure. A bathroom is also provided.
These are very popular.
Nutrient levels in Fossa alterna pit
soil
Analysis of Fossa
alterna pit soil reveals, like the Arborloo, a rich humus with high
levels of all the major nutrients required for plant growth, compared to normal
topsoil. Levels of the major nutrients: nitrogen are increased about 7 times,
phosphorus about 6 times and potassium about 9 times in studies undertaken in
Zimbabwe.
Analysis of Fossa alterna pit
soil compared to a mean of various topsoils
Soil source pH N* P* K* Ca* Mg*
Local topsoils (mean
of 9 samples) 5.5 38 44 0.49 8.05 3.58
Fossa alterna pit
soil (mean of 10 samples) 6.75 275 292 4.51 11.89 5.14
*Nitrogen
(N*) and Phosphorus (P*) are expressed as ppm and Potassium (K*), Calcium (Ca*)
and
Magnesium (Mg*) as ME/100gms. 1 ppm = 1
mg/kg. To obtain ppm from ME/100gms multiply
by 10
and the atomic number (39.1 for potassium).
These figures, taken from 10
different Fossa alternae, reveal how rich the mix of human excreta and
topsoil can be. “Fossa soils” are characteristically high in all the
major plant nutrients, notably phosphorus. In each of these tested cases only
poor local topsoil was added, without the inclusion of either wood ash or
leaves. The addition of wood ash, in addition to elevating the level of potash,
also helps to reduce odours and fly breeding in the pit. It also makes the
reaction slightly more alkaline. The addition of leaves greatly improved the
texture of the final product as well as elevating nutrient levels. This humus
has a good balance of nutrients and plants grow well in it. Normally it is
mixed with an equal volume of topsoil before planting vegetables.
The value of Fossa
humus, dug out of fully
composted pits was studied by mixing it with an equal volume of very poor sandy
top soils taken from a peri-urban settlement called Epworth, close to Harare,
and also a rural location called Ruwa. These are areas of exceptionally poor
topsoil, typical of so many locations in Africa. Without soil enhancement few
plant can grow in such soils. Soil
analysis of the poor soils (Epworth and Ruwa) enhanced with Fossa
alterna humus are shown below.
Analysis of poor soils (Epworth and Ruwa) with Fossa alterna pit soil
Epworth soil 4.1 23 54 0.07 1.72 0.50
Fossa alterna pit soil 6.4 197 299 2.94 26.64 4.77
Resulting mix of Epworth and FA soils 6.4 78 356 1.01 15.75 1.78
Ruwa soil 5.5 27 5 0.29 10.23 4.11
Fossa alterna pit soil 6.5 319 196 3.26 13.70 7.26
Resulting mix of Ruwa and FA soils 6.4 91 247 0.88 3.05 2.49
*Nitrogen
(N*) and Phosphorus (P*) are expressed as ppm and Potassium (K*), Calcium (Ca*)
and
Magnesium (Mg*) as ME/100gms.
Evidence
of enhanced vegetable growth.
In a series of simple
experiments vegetables like spinach, covo, lettuce, green pepper, tomato and
onion were grown in 10 litre buckets or basins of Epworth or Ruwa soil and
their growth was compared with plants grown in similar containers filled with a
50/50 mix of Epworth (or Ruwa) soil and
Fossa
alterna soil. When Fossa soil is excavated from the
pits it is normally mixed with an equal volume of local topsoil to prepare beds
or containers for planting vegetables. In each case the growth of the
vegetables was monitored and the crop weighed after a certain number of days
growth. The following chart showed the results of these trials. FA* denotes
soil taken from Fossa alterna pit. The extra growth is due to FA
enhancement.
|
Plant. Top soil type. Growth period. |
Weight at cropping Top soil only |
Weight at cropping 50/50 mix topsoil/FA*soil |
|
Spinach on Epworth 30 days. |
72 grams |
546 grams (7 fold increase) |
|
Covo on Epworth 30 days. |
20 grams |
161 grams (8 fold increase) |
|
Covo 2. on Epworth 30 days. |
81 grams |
357 grams (4 fold increase) |
|
Lettuce on Epworth. 30 days |
122 grams |
912 grams (7 fold increase) |
|
Onion on Ruwa 4 months |
141 grams |
391 grams (2.7 fold increase) |
|
Green pepper on Ruwa 4 months |
19 grams |
89 grams (4.6 fold increase) |
|
Tomato on Ruwa 3 months |
73 grams |
735 grams (10 fold increase) |
All these results clearly show
a dramatic and meaningful increase in vegetable yield resulting from the
enhancement of poor spoil (Epworth and Ruwa) with the Fossa alterna humus.
In similar trials with
maize, three seedlings were planted in 2 buckets containing Epworth soil and also
2 containing the Epworth/Fossa mix. After 3 months a total cob weight of
110 gms (6 cobs) was recorded for 6
maize plants growing on Epworth/Fossa
soil, but only 2.5 gms for
the 6 plants growing on the plain poor Epworth soil alone. Although this is a huge
increase, the Fossa alterna humus contained in the buckets did not provide
sufficient nutrients to take the maize to full yield. Urine was necessary in
these trials to provide the maize with sufficient nutrient to gain full cob
weight which can exceed 300 gms per cob (see later).
Spinach growing on poor sandy soil (left) and the same soil enhanced
with an
equal volume of humus taken from a Fossa
alterna pit (right).
Lettuce growing on poor sandy soil (left) and the same soil enhanced
with an
equal volume of humus taken from a Fossa
alterna pit (right).
Covo growing on poor sandy soil (left) and the same soil enhanced with
an
equal volume of humus taken from a Fossa
alterna pit (right).
Onion growing on poor sandy soil (left) and the same soil enhanced with
an
equal volume of humus taken from a Fossa
alterna pit (right).
Recycling
nutrients derived from the urine diversion method.
There are many systems of
urine diversion used throughout the world. Most separate urine from the faeces
in a urine diverting pedestal or squat platform. In most cases the urine is fed into a tank where it is stored for
later use. The faeces invariably fall into a vault where lime or wood ash is
also added leading to desiccation Where there are twin vaults, the pedestal is
moved from one vault to the other at approximately one year intervals to allow
the faeces to dehydrate. However urine can be collected in a variety of ways
other than in urine diverting toilets. Men can urinate into bottles direct or
into “desert lilies” (a funnel over a container placed in some discrete place)
and women into a variety of “potties” both separate from and attached to the
conventional flush toilet.
In a system called a “skyloo”
used in Zimbabwe, a urine diverting pedestal is mounted over a single vault and
the faeces fall into a 20 litre bucket, followed by a mixture of soil and wood
ash (mix 4:1). Urine is diverted to a plastic container. The bucket of faeces,
soil and ash is allowed to fill up and is then transferred to a “secondary
composting site” which may be a shallow pit, trench or jar, where more soil is
added. The most interesting system for secondary composting is the 30 litre
split cement jar, where the mix of faeces, soil and ash are transferred, with more
fertile being added after every application. 3 or 4 bucket fulls will fill the
jar which is then watered down and left to compost for about 4 months. At the
end of this period a very rich humus is formed. Vegetables (particularly
tomatoes) grow very well in this humus, as do flowers and a wide variety of
trees (which can be started off in the jars). Soil analyses of this humus
formed in the jars shows a well balanced and high level of nutrients.
Experience has shown that this humus is an excellent medium for growing a wide
range of plants.
Urine diverting toilet used by the writer
The urine diverting pedestal. Urine passes down the front through a
plastic pipe into a
20 litre plastic container. Faeces drop down vertically into a bucket
held in the vault
beneath. Dry soil and ash (and toilet paper) are also added to the
bucket.
Urine is collected in this 20 litre plastic container.
The brick built vault houses the bucket. The rear has a ferrocement
Door to gain access to the vault.
Rear vault access door removed. The 20 litre bucket is inside.
Emptying bucket contents into a 30 litre split cement jar
Several jars in which the mix of faeces, soil, paper and wood ash are
Composting. Plants like tomato thrive in such jars and often grow
spontaneously.
Analysis
of “skyloo” humus composted in 30 litre cement jars
Soil source pH N* P* K* Ca* Mg*
Skyloo humus (faeces,
soil, wood ash) 6.72 232 297 3.06 32.22 12.06
Fossa alterna pit soil (mean of 10 samples) 6.75 275 292 4.51 11.89 5.14
Local topsoils (mean of 9 samples) 5.5 38 44 0.49 8.05 3.58
*Nitrogen
(N*) and Phosphorus (P*) are expressed as ppm and Potassium (K*), Calcium (Ca*)
and
Magnesium (Mg*) as ME/100gms.
In many ways the humus
formed in the jars is similar to Fossa alterna humus, and has a well
balanced mix of nutrients. It has proved to be an excellent medium in which to
grow seedlings as well as mature plants. The living content of the “jar humus”
is very high – it is a most valuable product and enjoyed by many plant species
grown in it. These results testify to the great value of faeces without the
inclusion of urine. In fact both products are very valuable, the urine best as
a liquid feed applied diluted with water.
Using the nutrients in urine to enhance the growth of plants.
Each of us excretes about
580 kg urine per year (for adults) - about 1.5 litres per day, and this
contains many nutrients useful to plant growth. In recent figures released in
China by Gao, Shen and Zheng (2002), urine
contains 96.98%water, 0.53 % (3.08 kg/yr) nitrogen (mostly urea), 0.04% (0.23
kg/yr) phosphorus, and 0.14% (0.81 kg/yr) potassium. By comparison 113.7 kg of
human faeces are produced per year containing 80.7% water, 1.16% (1.31 kg/yr)
nitrogen, 0.26% (0.29 kg/yr) phosphorus and 0.03% (0.03 kg/yr) potassium (a low
figure for potassium compared to other analyses). Thus the urine produces 4.12 kg/yr NPK compared to the faeces
which produces 1.63 kg/yr. (thank you
Xiao Jun for offering this valuable information). Overall most nutrients
are released in the urine, but these new figures indicate that the annual
production of phosphorus is greater in faeces than in the urine.
Two 10 litre basins planted with rape and spinach. The basin on the left
has been fed with a 3:1 mix of water and urine, three times per week
interspersed
with normal watering. The basin on the right has been irrigated with
water only.
A problem faced with
urine when used as a feed for plants is that it has a very high proportion of
nitrogen and salt (Na Cl) compared to phosphorus and potassium. Most garden
fertilizers for vegetables contain more phosphorus than nitrogen. Phosphorus is
valuable for root growth, nitrogen for vegetative growth like leaves and
potassium helps the ripening and fruiting process. The great value of urine
lies in its universal availability and zero cost. Consequently it has immense
potential value and has been used for many generations as a plant food in some
countries, notably in the Far East. Because of its high nitrogen content it is
particularly useful for feeding leafy vegetables, which enjoy a high nitrogen
diet.
Plant trials with urine
The following trials were
performed on a variety of vegetables and maize using urine diluted with water
at a ratio of three parts water to one of urine as a liquid feed. Seedlings were planted in containers, either
10 litre buckets or10 litre cement basins and irrigated with water first for a
period (1 – 4 weeks) to stabilise in their new environment. Fast growing
vegetables like lettuce, spinach, covo and rape were irrigated with water first
for 1 – 2 weeks before urine application after transplant and tomatoes were
watered for a period of one month before urine application. Thereafter 0.5
litres of a 3:1 water/urine mix. was applied to the buckets or basins on each
urine application, this being the volume that the 10 litres of soil could
absorb. The 3:1 mix was applied three times per week in this trial interspersed
with regular watering at other times to keep the plants turgid and healthy.
Young seedlings do not tolerate the 3:1 mix well and need to stabilise before
the water/urine mix applied. They tolerate a 5:1 mix better. When the plants
are very young diluted urine can retard plant growth or even kill the young
plants.
For the maize trials,
carried out mostly in 10 litre cement basins, the urine was diluted in the
range 3:1, 5:1 and 10:1 with water. The plants were fed with urine either 3
times per week with the 3:1 mix (U1 application), once per week with the 3:1
application (U2), once a week with the 5:1 application (U3), once a week with
the 10:1 application or with water only. Plants being fed the water/urine mix
were also watered regularly at all other times to keep the plants healthy and
turgid. After a specified growing period, the crop was harvested and weighed. A
chart showing these various trials are given below. All watering was by hand -
using a watering can – the old and reliable method.
Plant trials with urine for various vegetables,
tomatoes and maize.
|
Plant and container |
Urine/water
application |
Duration of growth |
yield |
|
Lettuce (10 litre
bucket) |
water only |
30 days |
230 gms |
|
Lettuce (10 litre
bucket) |
3:1 urine. 0.5 li X
3 per week for 3 plants |
30 days |
500 gms (2 fold
increase) |
|
Lettuce (10 litre
bucket) |
water only |
33 days |
120 gms |
|
Lettuce (10 litre
bucket) |
3:1 urine. 0.5 li X
3 per week for 3 plants |
33 days |
345 gms (2.8 fold
increase) |
|
Spinach (10 litre
bucket) |
water only |
30 days |
52 gms |
|
Spinach (10 litre
bucket) |
3:1 urine. 0.5 li X
3 per week for 3 plants |
30 days |
350 gms (6 fold
increase) |
|
Covo (10 litre
basin) |
water only |
8 weeks |
135.5gms |
|
Covo (10 litre
basin) |
3:1 urine. 0.5 li X
1 per week for 3 plants |
8 weeks |
204 gms (1.5 fold
increase) |
|
Covo (10 litre
basin) |
3:1 urine. 0.5 li X
3 per week for 3 plants |
8 weeks |
545 gms (4 fold
increase) |
|
Tomato (10 litre
bucket) |
water only |
4 months |
1680 gms ( 9 plants) |
|
Tomato (10 litre
bucket) |
3:1 urine. 0.5 li X
3 per week for 3 plants |
4 months |
6084 gms ( 9 plants) (3.6 fold increase) |
|
Maize (M8 trial) (10 litre basins) |
water only |
3.25 months |
21 gms (mean 3 cobs) |
|
Maize (M8 trial) (10 litre basins) |
3:1 urine. 0.5 li X
1 per week for 3 plants (U2) |
3.25 months |
135 gms (mean 3 cobs) (6.4 fold
increase) |
|
Maize (M8 trial) (10 litre basins) |
3:1 urine. 0.5 li X
3 per week for 3 plants (U1) |
3.25 months |
318 gms (mean 3 cobs) (15 fold increase) |
|
Maize (M14 trial) (10 litre basins) |
water only |
3 months |
6 gms (mean 9 cobs) |
|
Maize (M14 trial) (10 litre basins) |
10:1 urine. 0.5 li X
1 per week for 3 plants u4 |
3 months |
62 gms (mean 8 cobs) (10 fold
increase) |
|
Maize (M14 trial) (10 litre basins) |
5:1 urine. 0.5 li X
1 per week for 3 plants u3 |
3 months |
138gms(mean 16 cobs) (23 fold
increase) |
|
Maize (M14 trial) (10 litre basins) |
3:1 urine. 0.5 li X
1 per week for 3 plants u2 |
3 months |
169gms(mean 18 cobs) (28 fold
increase) |
|
Maize (M14 trial) (10 litre basins) |
3:1 urine. 0.5 li X
3 per week for 3 plants u1 |
3 months |
211gms(mean 19 cobs) (35 fold
increase) |
Urine has a pronounced effect on maize, especially when grown in
containers
In the trials, maize plants were grown in 10 litre cement containers and
fed with
varying amounts of urine. In this case the plant on the right is being
fed with a
3:1 mix of water and urine (0.5 litres) three times per week. The maize on
the
left is irrigated with water only. The difference is striking.
Total yield of cobs from maize planted in 3 -10 litre basins. On the
left the maize was fed 1750mls urine per plant over the 3.5 month growing
period, resulting in a crop of 954 gms. A reduced crop resulted from reduced
input of urine (middle). Maize plants on the right were irrigated with water
only. This produced a very poor yield.
A single photo shows the effect of different amounts of urine applied to
maize plants over a 3 month period. On the left (U1) the plants have been fed a
3:1 water/urine mix three times per week (125 mls per plant per week). This has
led to a mean cob weight of 211 gms. The 3:1 mix was applied to the U2 group
once a week (40 mls per plant per week) and has led to a mean cob weight of 169
gms. A 5:1 mix was applied to the U3 group once a week (27 mls per plant per
week) and has led to a mean cob weight of 138.2 gms. A 10:1 mix was applied to
the U4 group once a week (15 mls per plant per week) and has led to a mean cob
weight of 62 gms. Those plants fed water only produced a mean cob weight of
only 6 gms. 99.4% of the total cob mass shown in this photo is derived from the
nutrients provided by the urine.
These various trials
reveal the great value of urine when used as a liquid feed for various plants,
and particularly for leafy vegetables (lettuce, spinach, covo). The application
of urine at the rate of 125mls per plant per week when diluted with 3 parts of
water (U1) increased the yield of lettuce by 2 – 3 times, spinach by
6 times, covo by up to 4 times. Even for tomatoes which prefer a
better balance of nutrients and certainly more potassium, crop output was
enhanced by a factor of 3.6 times compared to plants irrigated in
containers with water only. Maize too, responded very well to urine application
when grown in basins, under experimental conditions. Compared to maize grown in
basins without urine application the yield increases by factors which ranged
between 6 and 35 times when fed urine. These are significant improvement
in crop yield with the only source of available extra nutrients being released
from the urine.
These and other results from
an extensive series of maize trials reveal that the production of maize could
be increased on poor sandy soil, by the application of urine alone, but that if
the sandy soil had humus added, then the production went up further. Mean maize
cobs yields of 4.3 gms for poor sandy soil (Epworth) irrigated with
water only went up to 82.3 gms when soil was treated with urine only
(125mls per plant per week) and to 131.28 gms when the poor sandy soil
was mixed in equal proportions with Fossa alterna humus and also
treated with urine. This increase is partly due to the presence of the
nutrients in the Fossa alterna soil, but also due to the
increased number of nitrifying bacteria present in the humus which converts the
urea and ammonia in urine into nitrate ions which can be taken up by the
plants. The addition of Fossa alterna humus to poor Epworth soil
in equal proportions, but without urine treatment, only increased mean cob
weights from 4.3 gms to 27.9 gms. This indicates that the
presence of humus is an import requirement if the nitrogen in urine is to be
converted into a usable form which the
plants can take up.
Efficiency of use of urine
In all cases the yields of
both vegetables and maize was the highest when the highest dose of urine was
applied, but these were wasteful of urine. The results reveal that a lower dose
of urine was more effective in terms of gms of cob weight in relation to mls of
urine applied. These are best revealed in maize trial M14, where a total of 70
plants were examined. Figures are
given below for urine application to maize with corresponding cob yield and
also mls of urine required per gm. of cob yield.
Liquid feed No. weeks Total
urine applied per plant Mean cob weight
Water 12 none 6gms
U4* 12 180
mls 62
gms
U3* 12 324
mls 138.18
gms
U2* 12 480
mls 169.61
gms
U1* 12 1500
mls 211.25
gms
These figures reveal, as in
the M8 trial, that the maize cob output is related to the urine input and that
the highest urine input results in the highest output of cobs in terms of
overall yield. However the figures also reveal that the most effective use of
urine is not found in this highest dose rate as the chart below shows.
Mls
of urine required per gm weight of cob yield
Liquid feed Urine input per plant per week Mls urine required per 1 gm cob yield
U4 15mls 2,90
mls per gm cob
U3 27mls 2,34
mls per gm cob
U2 40mls 2,83
mls per gm cob
U1 125mls 7.10
mls per gm cob
Thus in terms of the most
effective use of urine, the U3 treatment was the most effective, as this used
20% of the maximum urine dose to produce 65% of the maximum cob output. The U2
treatment used 33% of the maximum urine dose to produce 80% of the maximum cob
output. These figures indicate that high doses of urine are not the most
effective way of using this liquid feed. But cob size is a factor of importance
considered by the consumer, and cobs produced in the U3 trial might have been
considered undersized. Thus one looks at the U2 treatment as the guide. If the
same amount of urine used to feed the U1 application was used to feed three
times the number of plants at the U2 application rate (about 40mls per plant
per week diluted with 3 X water), then the overall yield of cobs would have
been increased by a significant 2.4 times. In fact heavy doses of urine are
wasteful and not efficiently converted.
If urine is available in sufficient quantity, then an effective
treatment for maize would be U2 treatment for the 1st and 3rd
third months and U1 treatment for the second month. This regime would use a total
of 820mls urine per plant with the
possibility of little wastage of urine and producing a good cob weight per
plant. The largest cob produced in the trial weighed 356 gms. Remarkably
the plant grew 2.1 m high on just 100mm depth of soil.
Maize trials with urine
application on the fields are ongoing. Here the urine is applied neat in small
hollows made close to the plant, and the natural rainfall dilutes and flushes
it into the soil. These are complex experiments where the reaction of maize to
the urine depends on many factors including rainfall patterns, competition with
weeds and vegetables which are often planted next to the maize. Too much rain
and the nitrogen may be lost deeper down, too little rainfall and the urine may
not reach the roots. Also different soils react differently to the application
of urine, with some being better converters of the nitrogen than others. It is
hoped to report on urine trials on maize grown in fields at a later date.
Experimental maize field currently under investigation
These various experiments
reveal how valuable human excreta can be when used as a humus derived from
faeces or from a faeces/urine mix (Fossa alterna). They also
reveal the value of the urine when applied in a diluted form to a wide variety
of valuable crops.
Fossa alterna
humus when added to barren soil can provide an excellent medium for growing
vegetables in the back garden. Using the results from the trials, the annual
production of Fossa humus from the family toilet (approximately
600 litres/yr) when mixed with poor local topsoil might produce: 27 kg spinach
(first crop only – at least 2 crops can be reaped) or 17 kgs of covo
(first crop only – covo can be cropped for an extensive period) or 37 Kg rape
or 45 kg lettuce or 41 kg green pepper or 73 kg tomatoes or 40 – 50 kg onion.
Obviously there would be a mix of these crops produced in practice. As can be
seen from the equivalent weight of vegetables grown on poor soils alone, this
is a remarkable enhancement in vegetable production. What the eco-humus does in
addition to providing nutrients is to add humus to the soil, which has a great
value in its own right for increasing the effectiveness of urine
application. Urine application is much
less effective in barren soils which do not contain humus.
In terms of urine output, an
annual production of at least 1 000 000 mls (1000 litres) is possible from a
family of two adults and three children, even with some wasteage. There are
many ways of collecting urine in the homestead, filling bottles and potties
perhaps being the most likely in the absence of a urine diverting toilet. It is
interesting to speculate how much vegetable growth and maize cob yield would
result from the application of this annual production every year. The following
figures are calculated using data from the experiments described in this paper.
Crop mls urine required per gm of crop. Potential annual crop
Lettuce 5.5 mls
per gm of crop 181
kg/yr or
Spinach 5.0
mls per gm of crop 200 kg/yr or
Covo 7.3 mls per gm of crop 137 kg/yr or
Tomato 4.1 mls per gm of crop 243 kg/yr or
Maize 2.8 mls per gm of crop (U2 application) 352 kg/yr
Obviously urine
would have to be stored and made available for use at certain times of the year
when specific vegetables were growing. Also urine would be used for a variety
of applications by the enthusiastic gardener, which may include the enhancement
of flower beds as well as vegetables and trees. Whilst these figures are not
likely to be realised fully in practice they do reveal the huge potential of
urine application as an enhancer of vegetable and crop growth based on actual
results from the plant trials with urine.
The annual production of
both eco-humus from the family latrine (Fossa alterna or urine
diverting) and urine from various family sources, is only sufficient to enhance
the back yard family vegetable garden or a small maize field and no more. But this may represent, for each family, a
huge increase in vegetable production, especially in areas where the soil is
poor or access to manure or commercial fertilizer is difficult or expensive.
Barren gardens may be turned into gardens of plenty over the years.
The potential for increased
crop production is only one benefit to be gained from the introduction of this
new series of eco-toilets. The cheapness and ease of construction of both the Arborloo
and the Fossa alterna, makes possible the construction of a
family latrine at the home by the homesteaders themselves. This has been well
demonstrated in WaterAid’s excellent eco-san programme in Mozambique and also
in Malawi and Zambia. The construction of a simple concrete slab, using cement
and river sand is perhaps the most challenging technical difficulty. Yet in
Zimbabwe schoolgirls can perform this task with great ease, having been shown
the method. There is little very skilled workmanship required or heavy labour
needed to dig the shallow pits and the superstructures which are designed to
provide privacy only.
At a time when
rural, urban and peri-urban sanitation is in need of a practical uplift, and
perhaps a broader outlook is required, these eco-solutions may offer a ray of
hope, for they provide each family with a lot more than just a dumping ground
for excreta and garbage, which has been the case in the past. The links formed
between sanitation and the worlds of agriculture and forestry are practical and
exciting. They may have arrived just in time to give the sanitary world the
boost and novelty it now requires.
Acknowledgements
The writer wishes to
thank the following people for their support, advice and encouragement or for
promoting the concept of low cost eco-san in the field. The staff of the Friend
Foundation, in particular Mrs Christine Dean and Baidon Matambura, Moses Nyapokoto of Fambidzania, Marianne Knuth
of Kafunda Village, Annie Kanyemba, Jim and Jill Latham of the Eco-Ed Trust and
Ephraim Chimbunde, Edward Guzha and David Proudfoot of Mvuramanzi Trust in
Zimbabwe. Ron Sawyer, George Anna Clark and Paco Arroyo from Mexico. Ned
Breslin, Steven Sugden and John Kelleher and other colleagues in WaterAid, from
Mozambique, Malawi and Zambia and also Mbachi Msomphora from Malawi and Xiao
Jun from China. Obiero Ong’ang’a and Kinya Munyirwa from Kenya. Aussie Austin,
Richard Holden, Dave Still and Stephen Nash from South Africa. Almaz Terrefe
and Gunda Edstrom from Ethiopia – thanks for the early enlightenment. Uno
Winblad for pioneering this ecological view on sanitation and for his long
experience and valuable input. Many thanks to Paul Calvert for his valuable
insights and encouragement from India. Many thanks to Arno Rosemarin and staff
of SEI, Stockholm, who have supported the agricultural research sited in this
paper as part of the new EcoSanRes research programme. Many thanks also to Håkan
Jönsson and Björn Vinnerås for important inputs on the agricultural side and
urine use. Sincere thanks and much gratitude to the late and much missed Steve
Esrey from the USA. Ingvar Andersson and Rolf Winberg are much thanked for
their long support and personal encouragement. Also to Bengt Johansson and Sida
for their support which has made this new venture into ecological sanitation
possible. Finally to my wife Linda thanks for every possible support.
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