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The production of traditional African vegetables is an age-old tradition among the people of the northern region of Ghana. However, the knowledge base of traditional African vegetable production remains local due to a lack of research and policy support. Therefore, the adoption of improved technology among traditional vegetable farmers is generally low and impedes efforts to promote widespread cultivation, consumption and even commercialisation. This study aims at clarifying potential factors that determine the adoption of technologies by traditional African vegetable farmers in the northern region of Ghana. One hundred and five (105) respondents in five communities and across two administrative districts in the northern region were selected for an in-depth survey using a combination of quantitative and qualitative data collection methods. In addition, a logit regression was used to determine the effect of various factors on technology adoption by farmers. Among the factors, the educational level of a farmer, access to credit, farm size, experience in farming and access to extension support were found to be important factors affecting the decision of traditional African vegetable farmers to adopt improved technology. The results of this study can help enhance the effectiveness of policy re-orientation towards a more effective commercialisation of traditional African vegetables in Ghana and elsewhere.

To quantify carbon (C) and nitrogen (N) losses in soils of West African urban and peri‐urban agriculture (UPA) we measured fluxes of CO₂‐C, N₂O‐N, and NH₃‐N from irrigated fields in Ouagadougou, Burkina Faso, and Tamale, Ghana, under different fertilization and (waste‐)water regimes. Compared with the unamended control, application of fertilizers increased average cumulative CO₂‐C emissions during eight cropping cycles in Ouagadougou by 103% and during seven cropping cycles in Tamale by 42%. Calculated total emissions measured across all cropping cycles reached 14 t C ha⁻¹ in Ouagadougou, accounting for 73% of the C applied as organic fertilizer over a period of two years at this site, and 9 t C ha⁻¹ in Tamale. Compared with unamended control plots, fertilizer application increased N₂O‐N emissions in Ouagadougou during different cropping cycles, ranging from 37 to 360%, while average NH₃‐N losses increased by 670%. Fertilizer application had no significant effects on N₂O‐N losses in Tamale. While wastewater irrigation did not significantly enhance CO₂‐C emissions in Ouagadougou, average CO₂‐C emissions in Tamale were 71% (1.6 t C ha⁻¹) higher on wastewater plots compared with those of the control (0.9 t C ha⁻¹). However, no significant effects of wastewater on N₂O‐N and NH₃‐N emissions were observed at either location. Although biochar did not affect N₂O‐N and NH₃‐N losses, the addition of biochar could contribute to reducing CO₂‐C emissions from urban garden soils. When related to crop production, CO₂‐C emissions were higher on control than on fertilized plots, but this was not the case for absolute CO₂‐C emissions.

An experiment was conducted to find out the effects of some pre-germination seed treatments on germination of mango (Mangifera indica L.) seeds and initial growth of mango. Seeds obtained from a local mango variety at Nyankpala were sown in polyethylene bags filled with topsoil for the experiment. The four treatments used were; seeds sown without seed coats (SW), seeds without seed coats soaked in cool water of 5ºC for 12 hours before sowing (SSC), seeds without seed coats soaked in warm water of 15ºC for one minute before sowing (SSW) and seeds with seed coats sown to serve as the control (SC). Randomized Complete Block Design was used and each treatment was replicated three times. The parameters measured were germination percentage, height of seedlings, leaf length of seedlings, number of leaves and stem diameter of seedlings. Data obtained were analyzed using Analysis of Variance and the differences were determined by using Tukey-Kramer multiple comparison test. All the treated seeds recorded more than 80% of germination three weeks after sowing, with SSW recording the highest value of 91%. In general, the treated seeds performed significantly (p < 0.05) better than the control for the parameters studied. SSW is recommended for adoption since it performed optimally better than the other treatments in terms of number of leaves (7.67), leaf length (14.71 cm), leaf width (4.41 cm), stem diameter (1.82 cm) and plant height 20.86 cm).

Urban agriculture in developing countries contributes to food diversity and security of the urban population. Its importance will increase in the future because of fast-growing urbanization. Little is known about nutrient fluxes and balances of these high input agricultural systems, which are characterized by high fertilizer use, often combined with wastewater irrigation. Adding biochar to soil has shown the potential to decrease nutrient leaching, increase yields and nutrient use efficiency. Therefore, we installed lysimeters in a multi-factorial field experimental in Tamale, Northern Ghana. The treatments included a control (no amendments applied), biochar at 20 t ha−1, mineral fertilization according to the farmers’ practice and a combination of biochar amendment and fertilization. All treatments were irrigated with tap water or wastewater. The results show higher water losses under wastewater irrigation (+ 33%). The addition of biochar had no effects on nutrient leaching, balances or water flux. Leaching losses of nitrogen were around 200 kg N ha−1 when irrigation exceeded the crop demands. When irrigation was more appropriate, the leaching rates were 50–100 kg N ha−1. The leaching of Mg and Ca almost doubled in some seasons and negative mass balances under mineral fertilization entailed soil acidification. Nitrogen balances varied strongly depending on the season, irrigation water qualities or fertilization (− 50 to 222 kg NO3-N ha−1). We conclude that the high nutrient load associated with the commonly-practiced wastewater irrigation entails large leaching losses. These cannot be curbed by biochar application and should be accounted for in fertilizer management in urban vegetable production.

Rapid urban growth in sub-Saharan Africa challenges food supply of cities. As food and other organic matter are transported from production areas to consumption points, water, which has been used for their production, is transported virtually. This study aimed at determining the magnitude and sources of virtual water flows in food trade of two West African cities, in order to better assess food provisioning risks and water resource use and planning. To this end, flows of unprocessed food from local, regional, national and international sources were systematically recorded at all roads leading to Tamale, Ghana and Ouagadougou, Burkina Faso. The survey was conducted within two years covering the peak (November - December) and lean season (March - April), respectively, for six days in a row. Virtual water flows were computed by multiplying the flow quantities (t yr−1) by their respective virtual water contents (m3 t−1). Results showed that virtual water of all food commodities imported to Tamale and Ouagadougou were 514 and 2105 million m3 yr-1 respectively, out of which 68% and 40% were re-exported to other regions of the country. The data also showed major seasonal variation in virtual water flows across the year. Reflecting their dominating role in local diets, cereals contributed most to the total virtual water inflows in both cities. Southern Ghana is the major net virtual water importer from Tamale through cereals, legumes, vegetables, and livestock. The Northern Region of Ghana, on the other hand, is a net exporter of virtual water in all food groups apart from fruits. In Ouagadougou, large flows of virtual water were imported in cereals, specifically rice from Asian countries, via Ivory Coast.

Two proposed containers (50 kg-polypropylene sack and 50 kg-wooden crate) were compared with existing packaging containers (100 kg-polypropylene and jute sacks) to transport sweetpotato storage roots from major aggregation sites to distant urban market centers. The extent of breaks, bruises and the impacts, incurred by storage roots packaged in the different containers, were assessed. Additionally, at the urban market centers, the visual quality of the transported storage roots was evaluated by both aggregators and consumers. The benefit cost ratio (BCR) for each of packaging options was calculated to ascertain their profitability for sweetpotato roots transportation. The existing polypropylene/jute sacks resulted in significant major breakages in both years (p = 0.028, 0.016) after transportation for the Afram Plains-Accra route in truck. The donkey-driven carts or tricycles used for the Bawku-Bitou route did not show any significant (p > 0.05) influence on the storage roots contained in the existing polypropylene/jute sacks. The average impact recorded at both loading and offloading sites was significantly different (13.4 - 19.3 g vs. 0 - 30.0 g; p = 0.045) for all the containers. The proposed 50 kg-woodencrate had a significantly superior (mean rank of 127; p < 0.0001) visual quality compared with the other packages. All the packaging options showed profitability, because they had a BCR > 1.40, except for the 50 kg-wooden-crate. The 50 kg-polypropylene container delivered better quality roots to urban market centers than the existing packaging containers, and was more profitable than the 50 kg-wooden crates. The 50 kg-polypropylene container is recommended for the transport of sweetpotato storage roots in Ghana.

The research was conducted to establish the effects of triple super phosphate and rhizobia inoculant on yield of soybean (Glycine Max (L)) seed quality in the Northern region of Ghana. Multi-locational trials were adopted and three different locations were used. Soybean foundation seeds obtained from Savannah Agriculture Research Institute were subjected to three different treatments on the field. These treatments were TSP + Inoculant, TSP only, Inoculant only and a control plot as a check. Randomize complete block design was used to allocate the treatments to the various plots. Data collected from the field included: number of days from seeding to germination, flowering and pod formation; nodule formation; plant height, number of pods per plant per treatment (Pod load), number of days to maturity, seed weight at harvest per plant per treatment (1000 seed weight) and finally, the yield was determined after harvest. Results revealed that the treatments (TSP + Inoculant, TSP only and Inoculant only) generally enhanced growth, development and yield of soybean seed as compared to the control plots in almost all the locations. The application of Rhizobia inoculant contributed significantly to the development of the soybean plant. It aided the fixation of atmospheric nitrogen into the soil which improved its fertility that led to the significant increase in the number of nodules that were formed by the plant. The pod load was very high for all the treated plots. They were fully filled with seeds which were evidence in the yield obtained from the trials. TSP in combination with inoculants gave a very good yield of 2.66 Mt/ha and was significantly higher than all the other treatments. This result is a clear indication of how phosphorus fertilizer and inoculant positively affected the yield. Seed producers should be encouraged, in addition to good agronomic practices, to apply the recommended dosage of inoculant and TSP to their seeds and soybean fields respectively. This would lead to early maturity and high yields. Keywords: Soybean seed, Northern region of Ghana, Phosphorus, Inoculant, Yield

High urbanization pressure in Sub-Saharan Africa led to changes in the composition and configuration of rural and peri-urban agricultural production systems and to the establishment of highly market-oriented urban farming systems. Trees and shrubs, as a key component of agroecosystems, provide ecosystem services that support food security and agricultural productivity. However, the relationship between landscape structure, land use intensification, species diversity and functional diversity of woody plant communities particularly within the semi-arid environment of West Africa has received little attention. We combined GIS analyses and field sampling of woody plant communities of 72 agricultural systems located in rural, peri-urban and urban areas of Tamale (Ghana) and Ouagadougou (Burkina Faso). From a landscape perspective, peri-urban systems in Ouagadougou formed a transition or interacting zone between rural and urban systems and were shaped by urban growth dynamics whereas in Tamale peri-urban systems constituted a simplification of the rural parkland habitats and was mainly determined by agricultural intensification. Woody plant communities showed a high functional richness along the rural-urban gradient and provided a variety of ecosystem services, with food provisioning as main good. A trade-off between two regulating services, bio-control of pests and pollination services, could be observed within urban and in part within peri-urban farming systems. Hence, obtaining a holistic understanding of how landscape structure that is shaped by city growth and agricultural intensification affects ecosystem services is fundamental if West African urban farmers are to be politically supported in their efforts to manage landscapes effectively and to ensure agro-ecosystem multi-functionality and productivity.

Agricultural production needs to increase, particularly in sub-Saharan Africa, many rural people are undernourished, and the urban population is growing rapidly. It is worrisome that on many West African soils with low cation exchange capacity and soil organic carbon content, mineral fertilization is rather inefficient. Under these conditions, wherever available untreated wastewater is used for irrigation despite the potential health risks to producers and consumers. For intensively cultivated soils with high mineralization rates, biochar application has been advocated as a promising management option. However, the agronomic benefits of wastewater reuse in agriculture and its interaction with biochar have received only limited attention. This study therefore investigated the effects of mineral fertilizer application and biochar amendment at two water quality and quantity levels on soil moisture, plant nutrition and biomass production on a Petroplinthic Cambisol over 2 years. Rice husk biochar applied at 20 t ha−1 significantly increased fresh matter yields in the first five cropping cycles by 15%, and by 9% by the end of 2 years. Compared with clean water, wastewater irrigation increased yields 10–20-fold on unfertilized plots during the dry seasons, while a fourfold increment was observed in the wet seasons. This seasonal difference is likely a result of the high sequence of irrigation events during the dry season. In this study, fertigation with wastewater contributed significantly to plant nutrition and nutrient recovery while yield-increasing biochar effects disappeared over time. Soil moisture was enhanced by up to 9% due to biochar amendments under unfertilized conditions.

In urban and peri-urban agricultural production systems of Sub-Saharan African cities, diverse and functional complex weed communities may help to maintain biodiversity and ecosystem services and therefore indirectly support crop performance. However, effects of agricultural intensification and urbanisation on important weed diversity in the West African region had received so far little attention, although in Burkina Faso and Ghana up to 90 per cent of the population depends on agriculture as a main source of income generation. Hence, our research focussed on the analysis of changes in weed assemblages’ structure and function of okra fields that were cultivated under different management intensities and were embedded into the rural, peri-urban and urban environment of two West African cities: Ouagadougou (Burkina Faso) and Tamale (Ghana). We found a strong relationship between gender and market orientation of okra cultivation. Market orientation of okra farmers was also a major driver in shaping weed species assemblages and led to the development of a distinct weed assemblage in urban areas that even showed higher diversity in weeds’ function. Morphological plant traits (life form, seed properties) were most affected by agricultural practises; distribution pattern of ecological traits (seed dispersal mode, pollination vector) seemed to be influenced additionally by environmental characteristics with less entomophilous but more ornithochorous weed species on okra fields within urban areas. Our results revealed that the management of okra was highly variable and that this variation was influenced by farmers’ socioeconomic background leading to changes in soil properties. These in turn may alter the functional diversity of beneficial weed communities beyond changes in species richness by potentially harming the provisioning of ecosystem services such as pest control and pollination.

An experiment was carried out to study the sensitivity of amaranthus to different sources of soil nutrients and different amounts of irrigation water at different temperatures. Nitrogen (N) rich materials (compost/poultry manure) and carbon (C) rich material (biochar) used included poultry manure + rice husk biochar (PM+RB), poultry manure + sawdust biochar (PM+SB), rice husk compost + rice husk biochar (RC+RB), sawdust compost + sawdust biochar (SC+SB) mixed at 10 ton ha-1 N rich material to 5 ton ha-1 C rich material. Rice husk compost only, Sawdust compost only (at 10 ton ha-1 for each of RC and SC), NPK (400 kg ha-1) and no amendments as Control were also used. Two irrigation amounts (0.1124 mm and 0.225 mm per pot), were imposed resulting in 12 treatment combinations, in a completely randomized design with 4 replicates. The experiment was repeated under two different temperatures of 37 and 30°C in the glass house and pot house, respectively. Data on growth, yield, water use and nutrient leaching were collected. PM+RB produced the tallest plants (31.67 cm) with 0.1124 mm irrigation at 30°C. PM+SB treated plants had more leaves (17) with 0.1124 mm amount of irrigation water at 37°C. NPK treated plants gave the highest stem girth (5.87 cm) and highest SPAD value (42.5%) with 0.1124 mm amount of irrigation water at 37°C. Leaf area index was highest (43) at 30°C for plants receiving NPK and 0.225 mm amount of irrigation water. NPK treated plants gave the highest fresh biomass of 36.93 g at 30°C but lowest biomass (13.01 g) at 37°C. PM+SB gave the highest fresh biomass weight of 16.7 g at 37°C and highest volume of leachate (123 ml) with 0.225 mm irrigation water at 30°C. At 37°C, SC gave the highest leachate volume (166 ml). The study indicates a good potential for sustaining crop yield with organic materials under increasing temperature and declining water resources that may be associated with changing climate. Key words: Amaranthus, compost, biochar, climate change, irrigation frequency.

Experiments were carried out in the laboratory with the aim of accessing the effectiveness and parasitism by Trichogramma evanescens to prevent Corcyra cephalonica from infesting rice in paper and jute bags. Eight small jute or paper bags filled with 5 kg of organic rice grains were prepared and the openings sealed. Sentinel egg cards were prepared with thirty fresh eggs of C. cephalonica glued onto small pieces of paper cardboard. Eight sentinel egg cards were introduced into a plastic box measuring 60 × 40 × 21 cm, i.e four cards on top surface of the bag and the box bottom, respectively. Approximately 500 adults of T. evanescens were released 10–30 cm away from the egg cards. The control boxes contained no parasitoids; there were five replicates for all treatments and controls. Two experimental conditions were tested, i) placing a single T. evanescens-release unit with sentinel egg cards placed every 3–4 days without any further replacement of the release unit for three weeks, ii) both new host eggs and T. evanescens release units were replaced every 3–4 days. Mean emergence of C. cephalonica was significantly (p > 0.001) suppressed by the release of T. evanescens. There was statistically no significant difference on the number of emerged moths on paper bag compared to jute bag. All sentinel egg patches were visited by T. evanescens. There was no correlation between the distance (10–30 cm) at which the sentinel egg cards were placed away from the T. evanescens release point and the number of parasitized C. cephalonica eggs. There was no decrease in parasitism over time. The results demonstrate that T. evanescens has the potential for host-location ability and parasitism of C. cephalonica both on paper and jute bags. This parasitoid could be a promising candidate for the biological control of moth pests in bagged stored products.

This study reports and analyzes nutrient balances in experimental vegetable production systems of the two West African cities of Tamale (Ghana) and Ouagadougou (Burkina Faso) over a two‐year period comprising thirteen and eleven crops, respectively. Nutrient‐use efficiency was also calculated. In Tamale and Ouagadougou, up to 2% (8 and 80 kg N ha⁻¹) of annually applied fertilizer nitrogen were leached. While biochar application or wastewater irrigation on fertilized plots did not influence N leaching in both cities, P and K leaching, as determined with ion‐absorbing resin cartridges, were reduced on biochar‐amended plots in Tamale. Annual nutrient balances amounted to +362 kg N ha⁻¹, +217 kg P ha⁻¹, and –125 kg K ha⁻¹ in Tamale, while Ouagadougou had balances of up to +692 kg N ha⁻¹, +166 kg P ha⁻¹, and –175 kg K ha⁻¹ y⁻¹. Under farmers' practice of fertilization, agronomic nutrient‐use efficiencies were generally higher in Tamale than in Ouagadougou, but declined in both cities during the last season. This was the result of the higher nutrient inputs in Ouagadougou compared to Tamale and relatively lower outputs. The high N and P surpluses and K deficits call for adjustments in local fertilization practices to enhance nutrient‐use efficiency and prevent risks of eutrophication.

In response to changing urban food systems, short supply chains have been advocated to meet urban food needs while building more sustainable urban food systems. Despite an increasing interest in urban food supply and the flows of food from production to consumption, there is a lack of empirical studies and methodologies which systematically analyse the actual proportion and nutritional significance of local and regional food supplied to urban markets. The aim of this empirical study therefore was to compare the geographical sources supplying food to the urban population (“foodsheds”) in Tamale, Ghana and Ouagadougou, Burkina Faso, to record the supplied quantities and to assess the level of interaction between the sources and the respective city. The study was conducted over two years, covering the seasons of abundant and short supply, via traffic surveys on the access roads to the two cities, and in the Tamale markets, resulting altogether in more than 40,000 records of food flow. Results indicated that food sources were highly crop- and season-specific, ranging from one-dimensional to multi-dimensional foodsheds with diverse sources across seasons. Across the commodity-specific foodsheds, city region boundaries were established. Within the proposed city region a relatively large proportion of smallholders contributed to urban food supply, taking advantage of the proximity to urban markets. While food provided from within the city region offers certain place-based benefits, like the provision of fresh perishable crops, a larger geographical diversity of foodsheds appeared to enhance the resilience of urban food systems, such as against climate related production failures.

An experiment (Completely Randomized Design) was set up to determine the effects of Clay Pot Sub-surface Irrigation (CPSI) and spacing on the growth and fresh weight of lettuce (Lactuca sativa). The treatments were: CPSI with spacing; 15 x 15 cm, 20 x 20 cm and 30 x 30 cm. Control treatments were Watering Can Irrigation (WCI) with the same spacing as above. Treatments were replicated three times given a total of 18 experimental units. Eighteen large enamel basins of 50/20 cm (diameter/height) were filled with good topsoil and a clay pot buried neck deep in each of the basins. Seedlings were planted in all the eighteen basins. Five Hundred mL of wastewater was applied daily to plants in each container having either clay pot or watering can treatment. Plant height increased from 2.50 to 4.25 cm within 6 Weeks after Transplanting (WAT) under CPSI and only increased from 2.14 to 2.99 cm under WCI. The CPSI also supported better leave growth and fresh weight. The fresh weight of lettuce increased almost two fold under 15 x 15 cm spacing compared to 20 x 20 and 30 x 30 cm.

Experiments were conducted to determine whether applying seed vernalisation or gibberellic acid treatment, alone or in combination, can induce flowering in cabbage plants raised from seeds and rato...

The shea tree, Vitellaria paradoxa, is one of the most economically and culturally important indigenous tree species in the Sudano-Sahelian region. Its seeds contain a vegetable fat, internationally known as shea butter, which is widely used in edible, cosmetic and pharmaceutical sectors. Based on samples from 456 trees distributed in 17 locations across the species natural range from Senegal to Uganda, the fatty acid and tocopherol variation, and its relationship with geographic and climatic variables, was assessed in order to address the pattern and the origin of this variation across the natural range. Significant differ- ences between Western and Eastern regions for oleic, stearic acid, saturated-unsaturated acid ratio and c-tocopherol were identified that it is postulated maybe a result of genetic drift due to the evolutionary history of shea tree populations. Within regions the difference among stands was significant for most constituents; however the major part of the variation was observed among trees within stand (53-90 %). Relationships with climatic variables were not veri- fied, weakening evidence for clinal variation hypoth- eses suggested by previous studies.

An assessment of soil physical and chemical properties was carried out in Shea parklands of northern Ghana, selected along a North-south climatic gradient in 2011. The study sites were Paga, Nyankpala and Kawampe, which are located in the transitional and Guinea savannah zones of Ghana. For each site, 9 fallows and 9 cultivated fields were used, a total of 18 plots per site. Soil samples were collected at a depth of 0 to 30 cm and analysed for particle size distribution, pH, organic matter (OM), nitrogen (N), phosphorus (P), exchangeable bases, exchange acidity and effective cation exchange capacity (ECEC). The results revealed that the soils were strongly acid to neutral in reaction. The soils at Nyankpala parkland were comparatively more acidic (pH 80%) and deficiencies of basic cations were uncommon. Land use did not significantly influence the soil chemical properties. However, N values, were significantly higher in old fallows than in respect of new fallows and cultivated fields. Soil particle size distribution especially at Nyankpala was significantly influenced by land use, with fallow lands having more proportion of sand than that of cultivated fields. The extremely low P content (trace – 7.11 mg/Kg) of the soils might be due to P fixation which was commonly reported for soils in northern Ghana. However, if these soils were supplied with N fertilizers, seedling regeneration would be promoted due to the fact that increasing N levels and decreasing P levels in soil, results in significant increase in seedling dry weight as well as increasing uptake of total shoot N and C.

SummaryOsmotic priming of cabbage seeds with polyethylene glycol (PEG 6000), to prevent germination during a vernalising treatment, was investigated as part of a study into potential seed production in the tropics. A preliminary attempt to vernalise cabbage seeds had resulted in weak stemmed seedlings, with fungal infections, as a consequence of the non-primed seeds having germinated while still in the fridge at the low temperatures used for vernalisation (0° – 5°C). Two experiments to determine the effect of PEG 6000 on the viability and vigour of cabbage seed at non-vernalisation and vernalisation temperatures were carried out. In the first experiment, seeds of ten varieties of cabbage were imbibed separately in 302.44 g l–1 PEG 6000 in Petri dishes lined with filter papers moistened with PEG solution, or with distilled water as controls. The primed seeds were kept for 2 weeks at 25°C (non-vernalisation temperature) under an 8 h photoperiod, washed in distilled water and sown immediately into 4 cm-squar...

SUMMARY Cell membrane thermostability (CMT) and chlorophyll fluorescence (CF) were determined for ten lines of cabbage in order to select heat-tolerant varieties, to provide an improved method to screen for heat tolerance, and to determine whether there is a relationship between CMT and CF. Chlorophyll fluorescence parameters, especially variable fluorescence (Fv) and the ratio between Fv and maximum fluorescence (Fm), were found to be better than CMT for screening cabbage lines for heat tolerance. Fv values and the Fv/Fm ratio of stressed plants corresponded to high heat damage for the varieties ‘HRI 002605’, ‘HRI 003202’, and ‘HRI 007827’; and to low heat damage for the varieties ‘HRI 013011’, ‘HRI 005237’, and ‘HRI 006556’. The latter group may therefore be more tolerant of high temperature stress in the tropics. There were significant relationships (P < 0.05) between relative injury (RI), an index of CMT, and two of the CF parameters [miniumum florescence (Fo) and Fv/Fm] under stress conditions (35° ‐ 40°C). This suggests that parameters measured under stress temperatures are more reliable than those measured under non-stressed conditions when determining heat tolerance.