Urban agriculture improves people’s livelihoods in developing countries. An experiment was carried out to assess effects of soil fertility, mulch and tillage on soil organic carbon (SOC), aggregate stability (Ima), bulk density (BD), steady state infiltration rate (SSIR) and maize yield. Cattle manure (CM) + mineral N fertilizer, 0 or 5 t ha⁻¹ mulch and reduced tillage (RT) or conventional tillage (CT) treatments were imposed on sandy and red clay soils in Harare. After two cropping seasons, soil samples were taken from 0–5, 5–15 and 15–30 cm depths and SSIR was measured on site. RT significantly improved (p < 0.01) SOC and Ima in the 0–5 cm depth by at least 6% over CT. SOC and Ima increased by at least 13% under CM + mineral N fertilizer compared with sole mineral fertilizer. CM + mineral N fertilizer increased SSIR by at least 17% over sole mineral fertilizer, whilst mulching improved SSIR by at least 8% and RT by 27% in both soils. Maize yields significantly increased (p < 0.05) by at least 3.7 times in both soils under mineral fertilizer. Principal component analyses showed that yield could be predicted using BD on sandy soils and Ima and SSIR on red clay soils.

Poor soil fertility and increased frequency of mid-season droughts have made it difficult for urban farmers to get sustainable crop yields against a background of unemployment and reliance on urban agriculture for livelihoods in Harare and Chitungwiza. It is important to know soil fertility and water management practices used by urban farmers so that their performance can be evaluated and gender influence on their use assessed. The objectives of this study were (i) to identify soil fertility and water management practices used by urban farmers and their effect on maize yields and (ii) to determine the influence of gender on their use. Results showed a dominance of women (62.4%) over men (37.6%) in carrying out farming activities. Farmers used a combination of either poultry manure, sewage sludge or cattle manure with mineral fertilizers and attained an average maize grain yield of 1.5 t/ha. More women used organic fertilizers than men, but they applied lower rates leading to lower yields. Quantity of mineral fertilizer and sewage sludge used was significantly correlated with gender. More women than men used ridges and furrows, raised beds and mulching as water management practices. Development programs targeted for these farmers should consider gender in their design to ensure sustainability. Key words: Gender, manure, soil fertility, urban agriculture, water management.

Urban farmers in Harare grow vegetables in soils fertilised with poultry manure (PM) and sewage sludge (SS). Feed and storage management influence nutrient supply of these organic amendments. Nitrogen mineralisation of PM and SS were determined in a non-leaching and aerobic incubation experiment. Effects of these amendments on yield, nitrogen (N) and heavy metal uptake by vegetables grown in soils treated with 150 kg N ha⁻¹ from compound mineral fertiliser (7 N:14 P₂O₅:7 K₂O), PM (2.26% N) and SS (3.26% N) were studied. Phosphorus (P) and potassium (K) were added at rates of 50 kg P ha⁻¹ and 60 kg K ha⁻¹, respectively. A second crop was grown without adding amendments. Poultry manure mineralised faster than SS. Yield was significantly higher (p < 0.05) in mineral fertiliser amended soil for the first crop whilst organic amendments resulted in significantly higher yield in the second crop. First-crop nitrogen uptake increased by 53% and 100% (Brassica napus), 92% and 158% (Brassica juncea) over the control for SS and PM, respectively. Zinc, copper, cadmium and nickel uptake was higher with SS than in the other treatments and their concentrations were lower than European Union permissible limits. Poultry manure can be used in place of mineral fertiliser, whilst SS requires early or supplementary application of mineral N for early plant growth.

Wild foods and geophagic material are important in the nutrition of communities along Zimbabwe’s Great Dyke, a serpentinic ultramafic (SUG) and surrounding granitic geological (GG) environment. However, the health risks associated with consumptions of these in terms of toxic geogenic contaminants (TGC) is largely unknown. The study objective was to evaluate the health risks associated with consuming wild foods and geophagic materials from these environments. Health risk assessments were determined using Hazard Quotient, Hazard Index (HI) and Life Cancer Risk (LCR) for 10 TGCs, in wild foods and geophagic material. High human health risks (HI ≥ 1) were found in six wild foods and geophagic material under the SUG environment, compared with five wild foods and geophagic material under the GG environment. Wild foods and geophagic materials exceeded the tolerable risk level of 1x10-4. Their LCR values ranged from 1.22 x 10-3 to 8.77 × 10-2. All TGCs had a high LCR values above the tolerable risk level, except for Cu, Fe, Mn and Zn. Infusion reduced the LCR values for TGCs with only Pb in GG environment decreasing to below tolerable risk level. Communities should apply selective consumption and avoid F. sycomorus and geophagic materials with cancer risks.

Background: Wild foods and geophagic material are important in the nutrition of communities along Zimbabwe’s Great Dyke, a serpentinic ultramafic (SUG) and surrounding granitic geological (GG) environment. However, the health risks associated with consumption of these in terms of toxic geogenic contaminants (TGC) is largely unknown. The study objective was to evaluate the health risks associated with consuming wild foods and geophagic materials from these environments. Methods: Health risk assessments were determined using the hazard quotient, hazard index (HI) and life cancer risk (LCR) for 10 TGCs in wild foods and geophagic material. Results: High human health risks (HI ≥ 1) were found in six wild foods and geophagic material under the SUG environment compared with five wild foods and geophagic material under the GG environment. Wild foods and geophagic materials exceeded the tolerable risk level of 1 × 10⁻⁴. Their LCR values ranged from 2.11 × 10⁻¹ to 6.83 × 10⁻⁷. All TGCs had high LCR values above the tolerable risk level, except for Cu, Fe, Mn and Zn. Conclusions: Infusion reduced the LCR values for TGCs, with only Pb in the GG environment decreasing to below tolerable risk level. Communities should apply selective consumption and avoid F. sycomorus and geophagic materials with cancer risks.