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Successful demonstration activities in the use of toilet compost and urine as a source of nutrients for growing crops.

 

Peter Morgan

Aquamor, Harare.

 

As the concept of ecological sanitation becomes more well known throughout the world, so does the need for adequate demonstration that the processed excreta, whether it be toilet compost, urine or a combination of both, is valuable and can actually play a useful role in increasing food production. Whilst the recycling of nutrients derived from human excreta is one of the main tenets of ecological sanitation, many if not most ecosan projects around the world concentrate first on the provision of an ecological toilet, mostly of the urine diverting type, with recycling the products taking very much a secondary place in project initiatives. In practice and perhaps in the majority of projects, both urine and dried faeces are more conveniently “disposed of” into shallow pits. Urine may drain away unused. 

 

It must be accepted that not all users of ecological toilets are prepared to handle processed excreta at all – it is indeed a very foreign concept to most. Those who are prepared to handle the material are more likely to be “farmers” or “gardeners” and those that practice some form of agriculture already and already know the benefits of compost and manure. But even amongst this category, there is often doubt that urine and human manure is safe, let alone that it can actually increase the production of food.

 

Southern Africa is a sub-region characterised by a diverse range of peoples. The majority are poor with a much smaller proportion living under highly sophisticated conditions. For this reason a wide range of eco-sanitary hardware is used in the sub-region under the broadened umbrella of ecological sanitation, to cater not only for people accustomed to modern flush toilets, but also for those who may only have used the pit toilet before and in many cases no toilet at all.

 

The sub-region is also characterised by poor worn out soils, and unless they are fertilised or treated with manure, crop yields are often poor. Most people living in the rural areas will practice some form of subsistence agriculture and in several countries backyard agriculture is also practiced in both peri-urban and urban areas.

 

Where backyard agriculture is already practiced, commercial fertiliser or manure may be used to increase production, but an ever increasing proportion find these commodities either too expensive to buy or difficult to acquire. Under these conditions, the use of urine and compost derived from ecological toilets can actually make meaningful increases in production, both of vegetables and maize. Such practices can therefore have great practical value as well as forming strong links between the disciplines of sanitation and agriculture. And this of course is one of the most important aims of ecological sanitation. The back yard scenario is particularly suitable for the recycling of human excreta. In several countries in the sub-region, notably Malawi, Mozambique and Zimbabwe, backyard vegetable and maize production is commonly practiced, even in the urban and peri-urban areas. This is performed as a survival mechanism and perhaps because the forefathers have practiced it for generations. It is in such places where there may be huge potential for wider scale on-site reuse of processed human excreta. It is also possible that with the new source of nutrient rich materials derived from the toilet, those formerly disinterested in backyard gardening may develop an interest.

 

Those living in highly populated urban areas may not practice any form of agriculture at all - the population density may be too high and the practice of back yard gardening may never have taken root. Where backyard agriculture is not practiced at all, either because space does not permit or because there is no history of growing food in this way, excreta derived from ecological toilets must either be disposed of into some nearby pit or removed on a commercial basis to be dumped or processed elsewhere. The very considerable quantities of urine produced must also dealt with in some way.  In many locations of this type it is still possible to plant hardy trees or shrubs to gain access to the nutrients available in excreta.

 

At the present time there is little knowledge, even amongst avid back yard gardeners in Southern Africa, of the potential of processed human excreta to increase food production. Perhaps this lies in the wake of an era when commercial fertilisers were promoted with great vigour, not only by industry but also by government. Even as the era of organic farming and permaculture takes route so does the potential for reuse of all organic materials. But it is true to say that even at thus time, organic farmers and those who practice permaculture caste eyes of doubt about the recycling of human excreta.

 

Thus there is at this time a need to adequately demonstrate and convince those that already practice some form of agriculture that there may be potential in the re-use of processed human excreta, particularly in the back-yard environment. This paper describes a series of simple experiments where this increase in production of both vegetables and maize has been demonstrated and analysed in the backyard scenario.

 

Sources of nutrients

 

Urine contains most of the nitrogen produced in excreta and valuable amounts of potassium and phosphorus which are the main nutrients used in plant growth. Urine is collected in all urine diverting toilets and can also easily be collected in bottles, potties and other containers. Green vegetables and maize can benefit enormously from the large amounts of nitrogen found in urine.

 

Toilet compost can be collected from those urine diverting toilets where soil and ash is added to the excreta and where the mix is allowed to compost, either in the toilet vault itself or in a secondary compost site. Toilet compost can also be collected from shallow pit composters like the Fossa alterna where a mix of excreta (urine and faeces) together with soil, ash and preferably leaves too have been mixed and allowed to compost. Such compost resulting from this mix of ingredients can easy be dug out of shallow pits after a year of composting and mixed with topsoil. Trees also grow well on this material and planting trees on old compost pits offers perhaps the simplest method of recycling the nutrients in excreta. Fruit trees like banana and mulberry do particularly well. Toilet compost is less rich in nitrogen that urine, but it contains valuable amounts of all the major nutrients and is rich in phosphorus. It also adds humus and living material to barren soils. Dessicated faeces will also contain some potassium and phosphorus, but with minimal humus and living content. 

 

It is not difficult to demonstrate the usefulness of toilet compost and urine on the plants commonly grown in the sub- region. In the experiments described below the source of toilet compost was the Fossa alterna a popular low cost eco-toilet in countries like Malawi and Mozambique. An analysis shows that, compared to many top soils, shallow pit toilet compost and composted faeces from urine diverting toilets contain valuable nutrients which plants can use.

 

 

 

 

 

 

 

 

Analysis of compost derived from urine diverting and pit composting eco-toilets

 

Soil source                                                      pH        N*         P*         K*         Ca*       Mg*

 

Urine diverting toilet compost

(faeces, soil, wood ash)                                      6.72      232       297       3.06      32.22    12.06

 

Fossa alterna pit soil

Faeces, urine, soil, ash (mean of 10 samples)    6.75      275       292       4.51      11.89    5.14

 

Local topsoils

(Harare area. 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.  1 ppm = 1 mg/kg.

 

1. Effect of enhancing vegetable growth by mixing toilet compost with poor topsoil in containers.

 

In a series of simple experiments vegetables like spinach, covo, lettuce, green pepper, tomato and onion were grown in 10 litre containers filled with very poor local topsoil and their growth was compared with plants grown in similar containers filled with a 50/50 mix of poor topsoil and toilet compost. 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.

 

Plant and growth period.

Weight at cropping

Poor top soil only

Weight at cropping

50/50 mix topsoil/toilet compost

Spinach.  30 days.

72 grams

546 grams (7 fold increase)

Covo.  30 days.

20 grams

161 grams (8 fold increase)

Covo 2. 30 days.

81 grams

357 grams (4 fold increase)

Lettuce.  30 days

122 grams

912 grams (7 fold increase)

Onion. 4 months

141 grams

391 grams (2.7 fold increase)

Green pepper . 4 months

19 grams

89 grams (4.6 fold increase)

Tomato.  3 months

73 grams

735 grams (10 fold increase)

 

 

Left Photo: The photo shows spinach grown on poor soil (from Epworth) in left bucket compared to spinach grown on the same poor soil mixed with an equal volume of Fossa alterna soil (right bucket) after 30 days of growth. The harvest was increased 7 times (546 gms compared to 72 gms).

Right Photo: The photo shows covo grown on poor soil (from Epworth) in the left bucket compared to covo grown on the same poor soil mixed with an equal volume of Fossa alterna soil (right bucket) after 30 days of growth. The harvest was increased 4 times (357gms compared to 81 gms)

  

Left Photo: The photo shows lettuce grown on poor soil (from Epworth) in left bucket compared to lettuce grown on the same poor soil mixed with an equal volume of Fossa alterna soil (right bucket) after 30 days of growth. The harvest was increased 7 times (912 gms compared to 122 gms).

Right Photo: The photo shows onion grown on poor soil (from Epworth) in the left bucket compared to onion grown on the same poor soil mixed with an equal volume of Fossa alterna soil (right bucket) after 4 months of growth. The harvest was increased nearly 3 times (391gms compared to 141gms). Whilst this a significant increase in onion production, the best crops are produced on very rich organic soil. Onions are hungry feeders.

 

2.  Preparing and managing an eco-garden linked to an ecological toilet

 

In this case a small vegetable garden measuring 5m X 3.5m was prepared near an ecological toilet (Fossa alterna). The garden had been used previously for growing vegetables and was already partly fertilised. The compost produced from the toilet was dug out of the pit, after 9 months of composting in this case, and piled in heaps over part of the garden and then mixed in with the topsoil, thus enriching the soil further in that section. Another section was untreated with compost. Rape and spinach were planted in both treated and untreated sections of the garden. The main crop was harvested after 30 days, with smaller crops being harvested over the following 60 day period. The results are shown below, indicating an increased production for both spinach and rape.

 

Plant and growth period.

 

Weight at cropping. Existing vegetable garden. No. plants

Weight at cropping

Existing vegetable garden + toilet compost. No. plants

Increase in production over 30 day growth period

Spinach.  30 days.

2349 gms (24)

4153 gms (25)

(X1.76)

Rape. 30 days

1928 gms (25)

2478 gms (23)

(X1.28)

 

Plant and growth period.

Weight at cropping. Existing vegetable garden. No. plants

Weight at cropping

Existing vegetable garden + toilet compost. No. plants

Spinach. Second 30 days

508  gms (20)

429 gms (19)

Rape. Second 30 days

622 gms (22)

576 gms (19)

Spinach. Third 30 days

170 gms (18)

172 gms (12)

Rape. Third 30 days

186 gms (14)

179 gms (14)

Total vegetable (90days)

5763 gms

7987 gms (x 1.38)

 

Most of the nutrients available in the toilet compost were used up to provide the first major harvest after 30 days. The relative increase in production would have been greater had the soil been poor, as earlier experiments described in this paper show. By linking the eco-toilet with the eco-garden, a direct link is made between sanitation and agriculture. With a small family Fossa alterna about 700 litres of compost would become available annually for the garden. Fully composted or dehydrated faeces from urine diverting toilets could also be used. In fact the addition of a variety of composts (leaf, garden, toilet), could and should be added to such a garden to increase soil fertility and crop production. In addition, regular applications of diluted urine can lead to crop yields being sustained over a longer period for green vegetables like rape and spinach where the leaves are cropped regularly and new ones grow. Soaking the soil with a 5:1 mix of water and urine once a week, with intermediate watering, would be sufficient to sustain production for the active life of these valuable plants, which about 6 months. This method is described later for spinach and rape planted in containers.

 

 

Preparing the bed of the eco-vegetable garden. In this case an old vegetable bed is being prepared by weeding, digging down and mixing the soil over an area of approximately 15 sq.m. The vegetable garden was divided into three beds, each of about 5 sq.m. each.  Two heaps of Fossa alterna humus have been excavated. The 360 litres of humus was divided into two piles of 180 litres each. This volume of humus was sufficient to enrich two of the three beds in this vegetable garden. The humus was applied to each bed by distributing 12 piles, each of 15 litres over the bed with 0.5m between each pile. Thus 12 piles were made over each bed (12 X 15 litres = 180 litres). The humus was spread out over the surface with a hoe (badza) and then dug in and mixed with the local soil to a depth of about 10cm. This was then spread out over the surface as evenly as possible with a rake and then dug in and mixed with the topsoil.  

 

 

The beds were watered and then seedlings planted. In this case spinach and rape. 50 plants were sown in each of three beds making a total of 150 plants. After 4 weeks a good harvest of green vegetables has grown ready for the first cropping. In the bed mixed with extra Fossa alterna soil, the spinach harvest was increased by 1.7 times, and rape 1.4 times, despite  the existing bed being already quite adequate in terms of soil nutrients. After 6 weeks and two croppings the increase had been reduced slightly to1.6 times (spinach) and 1.3 times (rape). After 8 weeks and three croppings the total weight of spinach cropped on Bed A was 4754 gms, compared to 3027 gms on Bed B. After 8 weeks and three croppings the total weight of rape cropped on Bed A was 3233 gms, compared to 2736 gms on Bed B . Thus overall the application of the humus increased the spinach crop by 1.57 times and the rape crop by 1.18 times. The vegetables in this case were prepared for sale in neat bundles. Urine application, best diluted with water (3:1 or 5:1) once or twice a week to the plants would increase the output further.

 

3. Toilet compost as a potting soil

 

Toilet compost (particularly from the Fossa alterna) can also be used as a good potting soil. Its relatively high level of phosphorus and moderate level of nitrogen is good for establishing seedlings and young plants. It is an excellent medium in which to plant maize and vegetable seeds, which grow well without extra feeding prior to the later application of urine (diluted in the case of vegetable and undiluted in the case of maize).

 

The compost is dug out, sieved to extract stones and other material and then added to seeds trays or small pots in which the seeds are planted. In the case of maize planting, a hollow is made in the topsoil and a measured amount of toilet compost (500gms) is added. The seeds are planted in this compost. Toilet compost is valuable and can be stored in sacks after being dug out of pits or urine diverting secondary composting sites.

 

 

The toilet compost, in this case Fossa alterna humus is dug out of the pit and stored in sacks. To make potting soil, sieve this and also break up larger lumps. The sieved soil is ideal for the germination of seeds. In the photo on the right, fly larvae shells can be seen, attesting to the origin of the material. This potting soil is then added to a series of small plastic pots or seedling trays. The seeds are planted, in this case spinach. The small pots can be placed in a tray of water to keep moist. Without further feeding they grow into healthy seedlings. When the seedling is about 10cm high it can be transferred from the small pot into a 10 litre bucket or into a vegetable bed.

 

4. The effect of urine application on growth of green vegetables

 

Several experiments have been undertaken with the effect of diluted urine on vegetables grown in containers. The effect is shown clearly here on Rape and Spinach, two popular green vegetables in Zimbabwe. It should be noted that those plants held in containers and water fed only will eventually use up most of the nutrients held in the limited volume of soil, whilst those regularly fed with nutrients derived from urine will flourish by comparison, as the plant food in the form of diluted urine is regularly supplied. Thus the effect of urine application in containers is more noticeable than plants grown in beds.

 

4a Rape

 

Rape is one of the most popular vegetables grown in Zimbabwe. It is used a great deal in relish eaten with maize meal in combination with onion, tomato and meat. It responds well to being grown in containers which are fed urine diluted with water. In this trial, rape was fed diluted urine (3:1) twice a week. The urine application led to a 5 fold increase in harvest after 28days. This is an excellent response to urine.

 

Plant                            Liquid plant food         frequency of application          weight  harvested       

Rape                            water only                     normal watering                         160 gms   (9 plants)

Rape                            3:1 water/urine               0.5 litres 2 X per week                822 gms   (9 plants)

 

     

Left: Photo shows 3 basins (on left) which were water fed and on right 3 basins fed with a 3:1 water/urine mix, twice a week. The effect only became noticeable after 10 days treatment. After 28 days water/urine application the effect is very noticeable (photo on right with water treatment below and urine treatment above. Some of the basins are obscured. Rape yield was increased about 5 times.

 

 

Left: The relative yields of water fed and water/urine fed rape grown on 10 litre basins after 28 days application. The plants have just been harvested for the first time. Right: the same plants almost a month later just before the second crop was harvested. Yellowing and mauve colour on some leaves begin to show after 2 months of urine application at this rate, indicating that the plants are beginning to weaken. This is probably due to over application of nitrogen from the urine. Longer trials like this provide the best indications of the most suitable water/urine treatment under these conditions.  A weaker 5:1 application given to the plants once a week may be better in the longer term

 

4b Spinach

 

Like rape, several harvests can be taken from the same plant over a period of several months. It is ideally suited for growing in containers which are fed diluted urine as shown below. During the first month, the urine application (3:1, 0.5 litres, twice per week) led to a 3.4 fold increase in harvest after 28days, compared to water fed plants. During the second month the urine dose was reduced to 5:1, twice a week and during the third month and after, the urine dose was reduced further to 5:1, once per week. 0.5 litres of the diluted urine is applied to each basin (containing 3 plants) per treatment. The plants are watered at all other times.

 

Plant                           Liquid plant food      frequency of application      weight harvested

                                                                                                                        At 28 days      

 

Spinach (22plants)    Water only                  normal watering                      741gms

Spinach (22plants)    3:1 water/urine            0.5litres 2 X per week             2522gms

 

 

Photos taken of the 16 basin spinach trial.

Basins to the left of the green band are urine fed (3:1 water/urine mix with 0.5 litres of the diluted urine being applied to each treated basin twice per week). Those to the right are water fed only. Photo on left taken on 3rd December 2003 on the first day of urine treatment. Photo on right taken on 31st December 2003, 28 days after first urine treatment. The effectiveness of the urine treatment is very positive and very clear to see

 

The total collected spinach harvest of urine treated spinach on the left( 2522gms)  and water treated spinach on the right (741gms) after 28 days of growth.  This is a 3.4 fold increase in production. All  plants are watered at all other times. Spinach responds very well to this type of treatment.

 

5. Effect of urine application on maize planted on poor sand soils

 

Maize is a vitally important crop in Southern Africa and it responds remarkably well to the application of urine (usually applied undiluted). Extensive trials have been carried out on the effects of urine on maize growth (Guzha (2004), Morgan (2002). The growth of the plant and the final size of the cob is closely related to the supply of nitrogen if all other factors like rainfall and sunlight are not restricting. With standard commercial fertilisation the seed is planted together with 10gms a general fertiliser known as compound D (1:2:1) which contains about 1 gm of N. A second application of ammonium nitrate, (containing 34.5% nitrogen). provides another 3.4gms of N, making a total of nearly 5gms. Sometimes more nitrogen is applied as the grain filling stage begins. For most people in Southern Africa who do not have a rich protein diet, urine contains about 5gms per litre nitrogen (Håkan Jönsson pers. comm.). Thus one litre of urine provides about the same amount of usable nitrogen as a dose of standard commercial fertiliser.

In various pre-field trials with growing maize on poor sandy soil in containers (not reported here), there was a close relationship between volume of urine applied and final cob weight.  More urine led to larger cobs as the graph below shows.

 

 

The maize yield is related to the amount of urine supplied

 

Left:  The maize 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.  Right: Urine treatment also improves maize cob yield significantly. The total yield of cobs from maize planted in three 10 litre basins is shown. 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. This is a very high rate of urine application, but one happily accepted by the maize plants in the containers which were irrigated frequently with water to keep the maize plants healthy.

Part of the total harvest in the M14 experiment in basins showing the effect of urine treatment on maize. The maize plants held in basins which were fed only water produced a pathetic yield as the available nutrients were quickly used up by the maize. However where diluted urine was applied regularly, the growth of maize was considerably enhanced in proportion to the amount of urine added.

Also various experiments both in containers and in field conditions have shown that on porous sandy soils this one litre of urine is best applied in a series of smaller applications to avoid losses of nitrogen due to leaching following heavy rain during the active vegetative growth and grain filling stages. The rainfall pattern in Southern Africa is often characterised by heavy storms followed by lengthy periods without rain, as the graph below shows.

 

 

Applying urine

 

Where undiluted urine was applied a urine applicator made from a pill bottle with 125mls capacity was used in both backyard and field trials. The first 125mls was applied on planting day (day 0) under the seed (the seed is planted in 500gms of toilet compost). Further applications of 125mls urine were applied 0+3, 4, 5, 6, 7, 9, and 11 weeks to make a total of 1000mls.

 

Field Trial with maize in Epworth

 

Epworth is a large peri-urban settlement of about 200,000 people close to Harare. It was chosen as an experimental site to demonstrate the effectiveness of urine as an alternative to commercial fertilizer for maize production because it is characteristic of the conditions under which millions of people live both in peri-urban and rural areas in Southern Africa. Natural Epworth topsoil is sandy, porous, almost without nutrients and applied nutrients can easily be lost by leaching during heavy storms. Without commercial fertilizer or manure, maize and vegetable crops are generally very poor on soils of this type. However despite this backyard soil in Epworth is characteristically patchy with variable nutrient level. This is because over the years sections of land have been fertilized with manure and compost, and sometimes commercial fertilizer, particularly in delineated vegetable gardens. So there is some carry over of nutrients from year to year, particularly from manure and compost.

 

In the current trial a small existing backyard maize field was chosen which also housed an ecological toilet (Fossa alterna). 200 maize were planted and individually treated with a total of one litre urine during the vegetative and grain filling stages. A further 40 plants were not treated with urine. 40 additional plants were treated with standard fertilizer. At harvesting and for comparison a small sample of cobs was also taken from an adjacent field where no treatment of any type had taken place. Seed was planted in mid November and cobs harvested in mid March a period of 4 months.

 

 

 

 

Results

 

There was much variation between individual plants in all sections (apart from field 2) of the trial, mainly due to the variable existing nature of the soil even within each section of the experimental field, and probably due to earlier applications of manure, compost or fertilizer. This variation is characteristic of such fields and gardens. This variation was less evident in the urine fed section, where the treatment had a significant effect on maize growth and cob size – with more consistently larger cobs.

 

 

Section                                                          No. Plants     Mean cob      Equivalent

                                                                                                Wt. (gms)      grain wt. (gms)

Untreated (field 2)                                         15                    82.4                            41

Untreated (field 1)                                         36                    138.11                        75

Treated: commercial fertilizer (field 1)        34                    166.97                        97

Treated: urine (1 litre per plant – field 1)    196                 243.11                        148

 

Overall mean cob weight was increased by 1.76 times (138gms to 243gms) by urine application when compared to the untreated section. When plotted against grain weight, this increase in cob weight (X 1.76) represents a doubling in the yield of grain. When plotted on a graph, a 138gm cob yields around 75gms of freshly stripped grain compared to the larger 243gm cob which yields 148gms of grain.

 

 

The relatively high mean for untreated maize (field 1) was probably due to a sub-surface bed of manure or compost in one patch of the control zone which promoting healthy growth of a few plants making up 27% of the total cob weight in this section. The mean cob weight of urine treated maize (243gms) was about three times the mean cob weight (82gms) of sample cobs taken from another untreated field nearby, more typical of the area, where cob weights were more consistently poor. In terms of grain weight this is an increase of four times.

 

The urine was produced by the family itself and probably contained about 5gms/litre nitrogen, approximately the same as the nitrogen applied with commercial fertilizer. Residents in the area were impressed by the effect of urine treatment, which was plainly visible and cost nothing, but did require effort on the part of the householder. Put in simple terms the treatment of individual maize, planted on poor sandy soils, with one litre of urine spread over the growth period resulted in a doubling of grain output. This must be seen as a result worth the effort in such conditions.

 

The response of the maize in this trial to commercial fertilizer was surprisingly (and uncharacteristically) poor, with only a 1.2 times increase in mean cob weight.  This may have been due to the very poor and irregular rainy season characterized by single heavy storms followed by long periods without rain. Under these conditions soluble nitrogen (from urine or ammonium nitrate) may be quickly lost into deeper soil by leaching in these porous sandy conditions. The more regular weekly application of urine, undertaken in this experiment, appears to have partly overcome the leaching effect.

 

      

The field is prepared by digging and holes are made 30cms apart in rows 90cm apart. The 20 litre drum of collected urine is shaken up (to mix the phosphorus) and added to a 20 litre bucket. Date 5.11.2004

 

   

Using a dispenser, 125mls of urine is added to every hole

        

This is followed by one pea tin full (500gms) of toilet compost taken from the Fossa alterna or other composting toilet. Two seeds are then planted in the compost and pressed down and then covered with the topsoil. If seeds are in short supply then a single seed can be planted. Over 90% of registered maize seed will germinate. Another seed can be planted if a single seed does not germinate.

 

     

The seeds are pressed into the compost and covered with topsoil awaiting the rains

 

 

If two seeds had germinated, which was normally the case, one was removed and planted elsewhere. Urine is decanted from the larger 20 litre plastic storage vessel and poured into a bucket from where it is poured next to the plant with a small urine applicator made from a plastic pill bottle – volume 125mls.  

 

 

This photo was taken at the time when the last of the urine was applied. In the treated area (right) the growth of maize has been good and cobs are already forming. On the left the untreated area shows smaller and paler plants with reduced cob formation. The effect of urine is clearly visible.

Comparisons with maize growth in more fertile soil

 

For comparative reasons a similar trial was undertaken at the Friend Foundation in Tynwald near Harare. In this case a plot was chosen where animal manure (mainly donkey and dog) had been previously added to the soil over a period of time. This may be similar to a field or garden where kraal manure has been regularly added. This had the overall effect of enriching the soil, although the enrichment can be patchy.

 

Area 1 of the plot was planted with 70 maize which were treated with 1000mls of urine, applied over the growth and grain filling period in 5 applications. The seed was planted in 500mls of toilet compost. Area 2 of the plot was planted with 50 maize in toilet compost with a single 125ml application of urine. Area 3 of the plot was planted with 70 plants which were not treated with toilet compost or urine. The remainder of the plot (area 4) was planted with maize growing on manure treated soil without any further addition of urine or toilet compost. Maize was planted on 6th December 2004 and reaped on 24th March 2005. In each area the weight of each cob was measured. In area no. 4 which was the largest, a sample of 20 plants were measured. The results are as follows.

 

Area    Additional Treatment                                               total wt cobs  (no.)  mn.cob wt.

1          toilet compost + 1litre urine                                        24 354gms (68)          358.14

2          toilet compost + 125mls urine                                                18 050gms (51)          353.92

3.         Original manure only                                                   13 457 (66)                  203.89

4.         Original manure only                                                   6 708 (20)                    335.40

 

Under conditions where the soil is already enriched with manure, the presence of toilet compost and urine appears to have made little difference to the overall growth of the maize plants and final weight of cobs. The patchiness of the general area in terms of soil fertility is revealed by the differences in cobs weights from areas 3 and 4, neither of which were treated with either urine or toilet compost. The fertility derived from the manure enriched soil appears to have overridden the effects of toilet compost and urine in this experiment, where the application of either 1000mls urine or 125mls urine made little difference to the final yield of plants. The experiment also revealed that even within a small plot or field there can be much variation in the growth of maize plants depending on the nature of previous additions to the soil over localized areas. This was also revealed in the maize trial undertaken in Epworth.

 

In terms of cob size harvested, those from Tynwald were considerably larger than those from Epworth. The overall size of cobs harvested from all areas in the Tynwald soil was 305gms (overall mean) considerably larger than the overall mean of 211gms harvested overall from Epworth. This is entirely due to the quality of the soil in which the plants were growing and the fact that Tynwald soil had far more humus and was able to retain water better than the sandy soil of Epworth. Maize plants treated with one litre urine in Epworth had an overall mean size of 243gms compared to 358gms in Tynwald.  These simple experiments also reveal that the overall effect of urine on the growth of plants is not only related to the amount of urine applied, but also to the quality of the parent soil. The poorer the soil, the more noticeable the effect.

 

The real test of the practicability of this type of treatment comes during subsequent growing seasons following the demonstration. Will the urine treatment method be repeated and copied by others? For a small maize field of 200 plants a total of 200 litres urine was required and the man and wife of the household coped with this production during the period of the experiment. But if larger numbers of maize plants were treated in the same way, collection and storage of urine would need to take place prior to the planting of maize. Urine can be stored in 20/30 litre plastic containers. Whilst the cost of these containers would be high initially, their use would continue over many years, making the overall investment worth while.

 

Use of urine on fruit trees

 

The regular application of diluted urine on fruit trees can also have beneficial effects. For trees like banana, mulberry and mango, for instance, the weekly application of diluted urine (2 litres of urine + 10 litres water) can increase both natural vegetative growth and fruit production, although no statistical evidence is available at the present time. The health and size of plants is the best indicator, and this is revealed by the regular application of urine. Fruit trees also benefit from extra potash which can be supplied from applications of wood ash. The application of manure or compost and a leafy mulch can also help the growth of all trees.

 

Overall Conclusions

 

These simple experiments and demonstrations show very clearly that both toilet compost and urine can have considerable value in enhancing the yield of both vegetables and maize – the most important components in the diet of most people living in Southern Africa. This is particularly the case where plants are grown on poor soils, which are common in Sub Saharan Africa. The toilet compost and urine are best used in combination, each providing special benefits. The greatest value of the toilet compost is its living component, which can bring beneficial organisms of various types to a dead and worn out soil, and also to its humus like properties, which helps retain water and also to the valuable supply of phosphorus as well as other important elements. The conversion of urine nitrogen into nitrate which the plants require is performed by soil bacteria. The greatest value of the urine is its generous supply of nutrients, particularly nitrogen, which can increase the yields of green vegetables and maize in a spectacular way.

 

The experiments described in the paper are of the simplest type. They fall within the realm of bucket-science - literally! They are easy to replicate and demonstrate. Planting hardy plants like spinach in containers and applying urine to some and water to others quickly demonstrates the beneficial effects of urine. It is the demonstration of the effect which most impresses those yet to be convinced.

 

Simple as the experiments are, the implications are considerable. At its best the application of toilet compost and urine to the most important food plants of the sub-region on the worst of soils can lead to significant increases of harvest, particularly in the back yard garden scenario. The improvement of harvests can be achieved further by using human material in combination with other organic materials like manure or compost. In a continent where the majority live on poor soils and are also hungry – such considerations must be taken seriously.

 

Acknowledgements

 

The writer wishes to thank the following people for their support and advice on the agricultural aspects of ecosan. Christine Dean, Baidon Matambura, Felix Murenga, Marianne Knuth, Annie Kanyemba, Jim and Jill Latham,  Edward Guzha, Paco Arroyo, Almaz Terrefe and Gunda Edstrom, Håkan Jönsson, Björn Vinnerås, Anna Richert Stinzing, Paul Calvert, Arno Rosemarin and Ingvar Andersson.  Also to staff of SEI, Stockholm and Bengt Johansson and Sida for their support which has made this work possible.

 

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Jönsson, H., Vinnerås, B., Richert Stinzing A. & Salomon, E. (2004). Guidelines on the use of urine and faeces in crop production. SEI Report no. 2 of 2004.

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*Available on CD from SEI, Stockholm and WSP – Africa, Nairobi.