Chaya – Cnidoscolus aconitifolius

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Local context


Nicaragua is located in the middle of Central America and is the largest country in the region in terms of land area (130.373 km2). Population wise, Nicaragua is a medium-sized country for the region with more than 6 million inhabitants (WHO 2016). Nicaragua has a rich variety and high amount of natural resources, but despite this it is still one of the least developed countries in Latin America (World Bank, 2016; UNDP, 2016).
According to the Foundation for Sustainable Development (FSD), Nicaragua has a deficiency of safe drinking water even though it possesses the largest fresh water resources in Central America (FSD, 2016). This could contribute to health problems and a higher risk of disease-spreading (WHO, 2013). Because of economic development and with the help of new infrastructure projects the access to sanitation has increased in the country, but despite this, differences remain between urban and rural areas when it comes to access to clean water and sanitation (WHO, 2015; FSD, 2016).
Around 75% of Nicaragua’s forests have already been converted to pasture ground or is being used for large-scale mono agriculture (Alves Milho, 1996; FSD, 2016). There are still large areas of forest left in Nicaragua, and to slow down the effect from climate change such as erosion, it is vital that the remaining forests are kept intact. Large-scale farms and plantations in Nicaragua also has a history of heavy pesticide use which has led to contamination of people and the environment (Corriols, 2010). Livestock farming, cotton and banana plantations require large amounts of land and freshwater which both claim resources and potentially outcompete smaller and more sustainable agriculture and permaculture farming.


The region of Chontales was once part of the largest rainforest in Central America, but has now been significantly reduced (INEC, 2001). The forests of Villa Sandino which is the municipality where the experiments were conducted, have gone from 29 % of the land in the year of 1963 to only 1% in year 2001 (CIPP, 2009, INEC, 2001). The yields in Chontales are much lower than in the lowlands near the Pacific Ocean and many farmers in the area have abandoned the agriculture practices to engage in large scale cattle farming, a practice that generates low vegetation landscapes that is prone to flooding, mudslides and erosion during wet season, and wind-erosion in dry season. The expanding of cattle farming into the second growths forests is the main reason for deforestation in Chontales today (Klein, 2000; Yamamoto, Ap dewi & Muhammad, 2007).

Casa Montesano

This field study was carried out at the experimental agroecological permaculture farm Casa Montesano (11˚59ˊ70˝ N 84˚53ˊ06˝ E). The farm is located at 349 m above sea level in the area around Villa Sandino, in the Chontales region, central Nicaragua. The annual average temperature at the site is between 25 and 28 degrees Celsius and the climate can be described as humid tropical and the yearly average precipitation is around 2000 mm (Haller, 2011; INEC, 2011). The land use of the areas around Villa Sandino is dominated by either cattle farming or large-scale agriculture. Nearly half of the residents of Villa Sandino live under the poverty line per the UN definition, with many people working for large farm owners and livestock producers to be able to afford to purchase food (CIPP, 2009). The area mostly lacks sanitary infrastructure and water flush toilets and sewage systems are not widespread. Basic latrines are the common practice for deification.
CIPP is a Nicaraguan non-profit organization whose purpose is to support sustainable development in rural Nicaragua. The organisation informs and educates people and farmers in different permaculture projects to steer away activities from those sectors that contribute to continued deforestation. CIPP have provided courses in permaculture design and practices and initiatives have been taken to promote sustainable occupations such as beekeeping and small-scale farming (CIPP, 2009).

Urine diversion

There are several different methods to separate urine in latrines and outhouses to avoid mixing urine and excreta. For this study, the separating solution was selected, where a separator is placed on a current toilet base, leading the urine to storage outside of the outhouse via a PVC tube (Figure 1).
Figure 1. The process of the selected urine separation method showed complete with the separator, PVC-tube and jerry can.
When implementing urine separation, a storage solution for the urine is needed. The storage method and size could vary but for this experiment a 25-litre plastic jerry can with a sealed lid was chosen. This will ensure easy handling of the urine and the urine can be poured directly into a watering can or such. The use of a Jerry can also reflect the urine levels produced by a small-scale farm or a household (Sattari, 2013).

Experiment site

The experiment was performed on the experimental agroecology permaculture farm Casa Montesano, in the region of Chontales. The soil at the experimental site is classified as ultisol per the USDA definition (USDA, 2016) and it has a pH of 5.15 (Haller, 2011). Samples of the soil from the experiment site has previously been collected and analysed at the agriculture university laboratory in Managua. These results can be viewed in table 1.
Table 1. Physical and chemical characterization of the soil at the experimental site (Haller, 2011, approved for publishing).
To ensure that the influences from external elements such as weather, pests, livestock and diseases on the experiment are kept to a minimum, consulting local competence, including a gardener, was an important part when choosing the site, the crops and the methods for planting and watering. After consultation, the crops were planted directly in the soil and the experimental site was fenced off to keep any larger animals from entering.

Preparation and planting

The experiment site (Figure 3) is a lot of near 35 m2 that had been unused for over one year prior to the experiment. Before planting, the site was manually cleared of all vegetation with a machete. The experiment site was divided into two plots where one was to be fertilized with urine and the other not fertilized. Both plots received the same amount of added water.
At the experimental site, in total 12 different squares were created with an area of 1 m2 each. Each m2 was separated by 50 cm alleys on all sides, to allow easy access and avoid contamination from the surrounding squares. A 100 cm separation alley was created in the middle of the field to create a clear divide between the six squares that was being fertilized with urine, and the six squares that was not fertilized (Figure 2).
Figure 2. Planting scheme for the Beans and Chaya. The left half, coloured in grey, was not fertilized while the right half, coloured in yellow was fertilized with urine.
Figure 3. A picture on the planting process from the experimental site at casa Montesano.
In this experiment, a triplicate was used. For the beans, each square meter was prepared with 6 holes with the depth of 2 cm. The holes were lined up in two rows with approximately 20 cm spacing between the holes and 40 cm spacing between the rows. In each hole 3 pre-soaked beans were planted with a layer of surrounding topsoil for protection. In total 18 beans were planted per square meter. For the Chaya, 9 cuttings were planted in each m2, at a depth of 2 cm. The cuttings were lined up in 3 rows with 20 cm spacing between the holes and 20 between the rows. In total 108 beans were planted in 36 holes and 42 Chaya cuttings were planted (table 2).



When selecting the crops for this experiment several aspects were considered. One important aspect was that the crop should be locally occurring and could be utilized as a food crop. Other aspects considered were growth cycle, pest and disease resistance.
The common beans were selected since it is locally occurring and one of the most important source of food in Nicaraguan cuisine and eaten daily by many Nicaraguans. The plant has a relative short growing-cycle and creates seeds which is beneficial for comparing results.
In previous fertilization-experiments where the common bean was studied, damage from pests and insects has been reported (Haller, 2011). The beans furthermore respond moderately to Nitrogen fertilization (Maingi, Shisanya, Gitonga & Hornetz, 2001).
For those reasons, a second crop was selected, which would give the experiment a higher chance of showing effects of urine fertilization on crops. The second crop chosen is the perennial shrub Cnidoscolus aconitfolius henceforth referred to as Chaya, which is commonly used in Central American cooking as a spinach and is known to have strong resistance to pests, insects and weather. Both types of crops were locally available and could be traced back to the source ensuring no pesticides or modifications in the genealogy had been done. Seeds from recent harvested bean plants on a close by farm together with Chaya cuttings of similar thickness from Casa Montesano was collected.

Beans – Phaseolus vulgaris

A species of the bean, (Phaseolus vulgaris), and henceforth referred to as the common bean was sourced from a local family to ensure high quality and traceability. The common bean is, beside corn and rice the most important commodity for local food security and it is eaten almost every day (Munguía, Sotelo & Viana, 1996; Haller, 2011). It was also chosen since it can be important from a diffusion perspective if one of the most important commodities would show gains from urine fertilization. The common bean also has a relatively short growth cycle of under 2 months which is a requirement to be able to monitor the results of the experiment and if necessary in replanting crops that gets affected from external elements. The common bean has a long cooking time, which further eliminates risks that could be associated with urine fertilization.

Chaya – Cnidoscolus aconitifolius

The second crop chosen for the field study were the Cnidoscolus aconitifolius, commonly known as Chaya which is a leafy shrub that grows in Central America. The leaves can be used as a spinach and it is rich in protein, calcium and iron. It is known for being fast-growing, can survive harsh conditions such as drought and heavy rain and it has a good resistance to insect damage due to its content of a hydrocyanic acid in the leaves. Seeds from the Chaya plant is not normal, instead cuttings are the common method for plantation (CTA, 1999; CIPP, 2016). Due to the mildly poisonous acid in the raw Chaya, it is recommended for it to be cooked before eating, which is corresponding well to recommended risk handing barriers for urine fertilized commodities (Richert et al, 2010).

Urine as fertilizer

The use and characteristics of urine as fertilizer has been thoroughly researched in previous studies from around the world. Spångberg from Sweden’s university of agriculture (SLU) studied different rest- and by-products as fertilizers in the study “Plant Nutrients from Waste and By-Products – A life Cycle Perspective”. Human urine was one of the resources tested and is was deemed to be the best performing alternative to chemical fertilizers in many parameters (Spångberg, 2014). The use of urine as a fertilizer was also deemed to lower the energy use and the emissions of greenhouse gases compared to chemical fertilizers. Spångberg also states that one of the most important benefits from using organic instead of chemical fertilizers is that phosphate mining is not utilized and that instead phosphorous is recycled back into the soil (Spångberg, 2014).
Human urine as fertilizer is normally diluted to avoid burning the plants. According to Spångberg, 1 part urine with 10 parts of water is a good dilution rate (Spångberg, 2014), But anything from 1:0 to 1:15 would be possible depending on the local conditions and the amount of available urine (Richert et al, 2010). For successful implementation of the technology of urine fertilizing, clear and easy recommendations on the applications should be practiced. It is important to consider the plants different needs and cultivation stages: Some plants have greater need for nutrients in their early stages of cultivation and when entering their reproductive stage the take up of nutrients heavily declines. As a rule, the fertilization should be focused on the first ¾ of the time from sowing (Richert et al, 2010).
There are several different methods for applying urine fertilizers. It is not recommended to apply the urine directly on the plant and its leaves since this could lead to foliar burning due to the high content of ammonia in the urine (Richert et al 2010; Spångberg, 2014). If the fertilization is done during sunny days or when rain is absent, a small ditch can be created next to the plants were the urine could be poured. This method would help avoiding evaporation of the urine and prevent salination build-up in the soil (Rodhe, Richert-Stintzing, Steineck, 2004; Richert et al, 2010).
A good way to introduce urine as a fertilizer in new regions may be to start with experiments and demonstrations on local level. This will potentially show that the benefits of urine as a fertilizer is applicable on the local agriculture practice or in a household. The experiments could be simple demonstrations of the application and difference in yield between use of urine fertilizer and no fertilizer. It can also be more scientific performed experiments that can establish results in nutrient value and perfect application rate of urine to maximize the yield. If looking at urine fertilization from a eutrophication point of view, the leaching from reusing urine as a fertilizer is normally small compared to letting the urine stay in the pit latrine. It is also safer to use the urine as a fertilizer than letting it out in sewage systems since the soil both absorbs the nutrients and is better on degrading potential risks such as pathogens (Hammer & Clemens, 2007; Jönsson, et al, 2013).

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Urine diversion

Urine diversion in the context of this study refers to the separation of urine from the human excreta in an outhouse or similar rural toilet. There are several methods for how this can be done: It can be via a separate urinary or outhouse just for urine, or it can be done by just not urinating at all in the outhouse and instead urinate in a container such as a watering can or outside.
The potential benefits from urine diversion are many. When urine is separated from excreta, the volume of the latrine will fill up at a slower rate and the emptying frequency of the latrine will be reduced. Lower emptying frequency ensures easier handling of the excreta. According to Heimonen-Tanski & Wijk-Sijbesma it can also reduce the social stigma that is associated with the implementation and use of outhouses in the development world (Heimonen-Tanski & Wijk-Sijbesma, 2005). A lower emptying frequency also reduces risks with pathogens spreading, which is most critical during the emptying process.
Heimonen-Tanski & Wijk-Sijbesma’s study also concludes that urine diversion outhouses can have a positive effect on the hygiene with reduced smells and less manual labour with emptying the latrine. It is also a positive consequence that by separating the urine from the excreta you get a liquid fertilizer that can be used to get higher yields in small scale agriculture. It is also beneficial that the phosphorus in the urine is reused for planting instead of using chemical fertilizers were phosphate rock has been harvested in the creation of the fertilizer (Heimonen-Tanski & Wijk-Sijbesma, 2005; Cordell & White, 2011).
Human excreta and urine are rich in nutrients which is the reason why systems to collect and distribute it as a fertilizer has existed throughout history (Richert et al, 2010). If the excreta and urine are separated the excreta will be more concentrated due to not being mixed with the high amount of water that urine contains. In the composition of human waste, most of the nitrogen and phosphorous is available in the urine, while most of the bacterial pathogens and other hazards are to be found in the excreta (Richert et al, 2010). If the human excreta are being composted and used as manure, it should however be taken in to consideration that the lack of the nutrients in the excreta when the urine has been separated will affect the overall nutrition value of the compost. However, when mixed with excreta, most of the nitrogen in urine is transformed into nitrogen gas or ammonia and not suitable for soil fertilization, which would be an argument that it is better utilized in urine fertilizer than in compost (Kirchmann & Pettersson, 1995; Schönning, 2001)
Urine separating toilets can be a valuable investment, primarily in developing countries and foremost in rural areas were the standard water flush toilets not yet has been implemented. A urine separating toilet investment does not have to include any real expenses but can be implemented in different ways depending on the materials and practices available in the local contexts. Another important benefit with implementing urine separating systems is that no claim on freshwater is needed. Also, contrary to water flush toilets, a urine separating system means that valuable nutrients don’t get lost or deteriorate in sewage systems.
In Nicaragua, several different implementations of urine separation were discovered during the field experiments. In a Permaculture farm, called Bona fide and located on the island of Ometepe. A system is implemented with an outhouse with two toilets, one for human excreta and one for urine only, making it easy for both sexes to use sitting down. The urine is led out via a pipe and stored in a container for use as a liquid fertilizer on the farms plants and nursery (Figure 4). In another permaculture farm and combined eco-hostel, also on the Ometepe Island, a system was put in place were users are requested to use a separate urinal instead of urinating in the many outhouses on the farm. The urinal is a squat toilet, which leads to unequal use between the sexes were men stands up and women must squat. It also is some distance between the urinal and the other toilets making it tediously for proper separation.
Figure 4. Storage solution for urine at the permaculture farm Bona fide, on Ometepe island.
To separate the urine with the urinal method or physical separation has its benefits with low to no implementation cost and a straight forward use. The drawbacks with voluntary urinary is that it makes it harder to control that no urine is mixed with the excreta since it is easier to ignore the separation process if not proper understanding or motivation for the system is shared by the users, for example in a public toilet. With a urine separating device that separates the urine in the outhouse, the separation will be constant and automatic, and both sexes can use the toilet in the same way as if there were no separating to be done at all.

Other studies

Today, results from studies and projects around the world where the use of urine fertilization has been tested are widely available. Even though the amount of results coming in are growing there is still knowledge gaps existing, leading to the need of more studies in different parts of the world and to reach out with the available results to a broad spectre of people, both professionals and the public (Richert et al, 2010). Training sessions in Nepal in 2011 that consisted of 4 whole day sessions for the local farmers increased the rate of urine separating households from 37% to 65%. The training included information about the benefits of urine application. One example that was used to convince the farmer was a local who grew spinach that when it was fertilized with urine grew in a faster rate and turned out both greener and when it was cooked it had a better taste. Human urine has for a long time been utilized as fertilizer frequently in small scale farming and its likes, but its practices has not been much documented. In South Africa, diluted urine was used as a fertilizer for corn, tomato, cabbage and spinach cultivation. It was found that urine was a good source of nutrients for the crops.
In South Africa, the effects were tested of very high levels of urine being applied to vegetables. The results show that, under the local conditions, very high rates of urine led to increased salinity in the soil and lower yields (Richert et al, 2010). In another study conducted in South Africa the cost and benefits of using separated urine as a fertilizer compared to using chemical fertilizer and no fertilizer on crops showed that even though the construction costs of urine separating toilets was higher, it had the greatest total economic benefits and it was recommended as the solution for improving soil fertility. A similar study in Niger compared the cost of constructing a urine separating toilet to the value it created in terms of fertilizers. The results showed that the advanced construction would pay for itself within 2 years from only the value of the fertilizers that could be sold on the local market for less than the chemical fertilizers (Richert et al, 2010).
In Sweden, urine was tested as a fertilizer on Barley in a study in the end of the nineties. The study concluded that the N effect of urine was corresponding to around 90% of that of chemical fertilizers. Studies in Germany also on Barley showed that the fertilizing effect of urine was higher than that of mineral fertilizers (Richert et al, 2010).
A study on sanitation in Bangalore, India concluded that urine diverting toilet systems was a contributor to better sanitation and at the same time, reusing the urine as a fertilizer helped the local farmers to save money and achieve better food security. Studies in Ghana during 2004-2005 investigated the nutrient efficiency of urine compared to chemical fertilizers. It concluded that, as a source of nutrients the efficiency of the urine was at a minimum the same as to chemical fertilizers (Richert et al, 2010). In Zimbabwe urine fertilization was applied to plants grown in cement basins and compared to unfertilized plants.
The application was 0,5 liters of a 3:1 water/urine mix which was added three times a week.
The results showed larger plants when urine was added.
Urine fertilization compared to both no fertilizer and chemical fertilizer on cabbage was studied in Finland and the results showed that the growth and size was higher in the urine fertilized cabbage compared to non-fertilized and chemical fertilized cabbage (Pradhan, Nerg, Sjöblom, Holopainen & Heinonen-Tanski, 2007). The study also concluded that damage from insects was lower on the urine fertilized compared to the chemical fertilized cabbage. The study also found that using urine as a fertilizer did not affect the taste or the hygienic quality of the cabbage (Richert et al, 2010). Cucumber was chosen in another Finnish study where urine separation was used to create fertilizer value. The urine fertilization was leading to slightly larger yields than its chemical counterpart. The cucumber was also tested for  pathogens and none was find. In a blind test on the taste more than 50% of the testers could identify the urine fertilized cucumber but did not prefer one over the other. In Mexico urine was tested as a fertilizer to be used inside greenhouses on lettuce. Compared to no fertilizer at all and chemical fertilizers, the urine was concluded to give the highest cultivation and had the best availability of Nitrogen for the crops, it was also tested in Mexico on amaranth were the results showed that together with different types of manure, human urine was giving the highest yields, while standalone urine gave around 40% more yield than the non-fertilized control (Richert et al, 2010). In India, urine from separating toilets was used on banana plants and at the rate of 50 liters per plant the average bananas per plants was 185 compared to 110.3 for the chemical fertilized plants. If potassium was added to the urine fertilization scheme, the average went up almost 50% compared to the results of the chemical fertilized plants (Richert et al, 2010).
Burkina Faso was the place for a test where urine from the households were collected and treated by being stored for certain times. After storage, the urine is sold as a liquid fertilizer to the farmers in the area. To avoid the stigmatization of urine to be a factor the collection from the household were done in yellow jerry cans and after storage the now fertilizer was poured in green jerry cans (Richert et al, 2010). Projects in Burkina Faso also included building 1000 urine diversion toilets both for households and public uses.

Table of contents :

1. Introduction
1.1 Background
1.2 Problem
1.3 Purpose
1.4 Objectives
1.5 Limitations
2. Method
2.1 Local context
2.1.1 Nicaragua
2.1.2 Chontales
2.1.3 Casa Montesano
2.1 Urine diversion
2.3 Experiment site
2.4 Preparation and planting
3.1 Crops
3.1.1 Beans – Phaseolus vulgaris
3.1.2 Chaya – Cnidoscolus aconitifolius
3.2 Urine as fertilizer
3.4 Urine diversion
3.5 Other studies
3.6 Nutrient value in urine
3.7 Chemical Fertilizers
3.8 Peak phosphorus
3.9 Risks with urine fertilizer use
3.9.2 Pathogens
4. Results
4.1 Urine separation
4.2 Urine fertilization
4.3 Yield
4.4 Spreading the technology
5. Discussion
5.1 Experimental results
5.4 Future studies
7. Acknowledgements


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