References
- ATSDR (Agency for Toxic Substances and Disease Registry). 1999. Health guidelines comparison values (first quarter of 1999). Atlanta, GA: ATSDR.
- Crush J, Hovorka A, Tevera D. 2010. Urban food production and household food security in southern African cities. Urban Food Security Series no. 4. Cape Town: African Food Security Urban Network.
- Douglas BF, Magdoff FR. 1991. An evaluation of nitrogen mineralization indices for organic residues. Journal of Environmental Quality 20: 368–372. doi: 10.2134/jeq1991.00472425002000020006x
- Falen CLJ. 2003. Organic fertilizers. Crop Production and Soil Management Series FGV-00349. Fairbanks: University of Alaska.
- Hanlon EA. 1992. Determination of total Mn, Fe, Cu and Zn in plants by atomic absorption techniques. In: Plank OC (ed.), Plant analysis reference procedures for the southern region of the United States. Southern Cooperative Series Bulletin 368. Athens, GA: Georgia Agricultural Experiment Stations, College of Agricultural and Environmental Sciences, University of Georgia. pp 48–50.
- Jansson SL. Persson J. 1982. Mineralization and immobilization of soil nitrogen. In: Stevenson FJ (ed.), Nitrogen in agricultural soils. Madison: American Society of Agronomy. pp 229–252.
- Mapanda F, Mangwayana EN, Nyamangara J, Giller KE. 2005. The effect of long term irrigation using wastewaters on heavy metal contents of soil under vegetables in Harare, Zimbabwe. Agriculture, Ecosystems and Environment 107: 151–165. doi: 10.1016/j.agee.2004.11.005
- Myers RJK, Palm CA, Cuevas E, Gunatilleke IUN, Brossard M. 1997. The synchronization of nutrient mineralization and plant nutrient demand. In: Woomer PL, Swift MJ (eds), The biological management of tropical soil fertility. New York: John Willey and Sons. pp 81–116.
- Okalebo JR, Gathua KW, Woomer LP. 2002. Laboratory methods of soil and plant analyses: a working manual (2nd edn). Nairobi: Sacred African Publishers.
- Rowell MD. 2001. Decomposition and nitrogen mineralization from biosolids and other organic materials: relationship with initial chemistry. Journal of Environmental Quality 30: 1401–1410. doi: 10.2134/jeq2001.3041401x
- Sims JT, Stehouwer RC. 2008. Recycling of nitrogen through land application of agricultural, municipal and industrial by-products. In: Schepers JS, Raun W (eds), Nitrogen in agricultural systems. Madison: American Society of Agronomy. pp 769–774.
- Sommers LE, Nelson DW, Parker C, Graveel J. 1980. Optimum utilization of sewage sludge on agricultural land. Annual Report from Purdue Agriculture Experimental Station to Regional Project W-124. West Lafayette: Agricultural Experiment Station, Purdue University.
- Vhurumuku E. 2000. Measurement of food security and vulnerability in Zimbabwe urban areas. USAID Famine Early Warning Systems Network, Harare, Zimbabwe. 10 pp. Available at http://pdf.usaid.gov/pdf_docs/Pnadd548.pdf [accessed 18 February 2014].