Ecological Development of
Valley View University, Accra, Ghana

Increasing the Efficiency of Agroecosystems

The challenge in crop production is to design a strategy that, despite the extremely harsh environmental conditions, enables the farmer to grow healthy produce in a sustainable way while at the same time makes efficient re-use of nutrients and water contained in organic wastes possible.
Low yields in the region are primarily due to limited water availability and poor fertility of the highly weathered and nutrient depleted soils. Annual precipitation is below 800 mm and varies strongly between years. Since local evapotranspiration, in the magnitude of 1600 mm, exceeds rainfall the climate is semi-arid. Large scale irrigation is not feasible due to the absence of natural water resources. Fertiliser use by farmers is marginal as a result of restricted buying power, frequent supply shortage and ignorance of the plant-nutrient interaction. To ameliorate savannah agriculture the allocation of water and nutrients to crops is among other duties required.

Water conservation measures at VVU latterly include ditches and mounds for rain water harvesting, terraces as well as tight ridging to prevent uncontrolled rainwater runoff. Further it is intended to increase the soil's water holding capacity and infiltration rate through the application of compost.
A key feature of the project is its alternative sanitation technology, allowing nutrients and water to be recovered for the use in agriculture. These technologies, including dry urinals and water saving separation toilets, collect urine or urinewater mixture of which both are disinfected by storage and consequently ready to be utilized as fertiliser. Flush water with faecal matter from the separation toilet is deposed either into a biogas plant or peripheral septic tanks. The developing sludge can be used as soil conditioner after undergoing composting treatment. Co-composting of household wastes, yard trimmings and tree-prunings with sludge is due to its water content rain independent. Grey water (from sink, shower, wash basin and laundry) can be re-used to irrigate crops.
Through implementation of these resource conserving technologies, a complex circular flow system is established. Nutrient and water entering the campus are collected in shared facilities, processed and used in agriculture. Nutrients cycle back to the cafeteria with the produce. In order to maximise efficiency losses through percolation and surface discharge must be minimised. To ensure high environmental and hygienic standards, establishment and routine operations are accompanied by scientific evaluation of nutrient flows, pathogen load and acceptance.

 

 

 

  

2: Urine Tank    

 

 Kontakt


   Prof. Dr.-Ing. D. Glücklich    Dipl. Ing. Nicola Fries

   Bauhaus-Universität Weimar    99421 Weimar

 

 e-mail


   oekolog.bauen@uni-weimar.de

 

 


3: Compost Pile  

Diversification within Agroecosystems

VVU reserved on campus 20 hectares for farming. The division of the area into four productive sections enables a continuous supply of a variety of produce and offers at the same time a wide range of options for the application of sanitary products. Further, diversity of species with specific temporal water demand and dissimilarity in drought-resistance reduces the risk of total loss during times of aridity, while assuring high yields when there is ample precipitation:

  • Agroforestry, including drought resistant tree species, e.g. cashew, mango, starfruit, guava and oranges, will occupy a major portion of the land [6]. Cultivation of trees allows for the productive use of water supplied by irregular precipitation and constitutes a persisting sink for urine based fertiliser and compost.
  • Staple food crops e.g. maize and cowpea are cultivated under rain-fed conditions during both long and short term rainy season (March to July and September to October). Research concentrates on the investigation of the most suitable model for growing cereals and legumes, fertilised with ecological sanitation products under local conditions.
  • In a fruit orchard, more water demanding species, e.g. paw-paw and banana are grey water irrigated and intercropped with pineapples and passion fruit.
  • Vegetable cultivation is supported by irrigation with grey water. Main research will focus on techniques enhancing high water productivity.




4-5: Maize Field