Heavy Metal Pollutants and their Concentrations in Fish (Barbus Species) in Sosiani River, Kenya

The presence of heavy metal pollutants in fish caught from River Sosiani, a small river that passes through Eldoret town, Kenya was studied in February and September, 1995. Heavy metals studied were: Cadmium, Chromium, Lead, Zinc, Copper, Manganese, Iron, Calcium, Magnesium and all these were detected in fish tissues, such as muscles, gills and liver, using Atomic Absorption Spectrophotometer. The levels for different metals varied for different tissues. For example in muscle Cadmium level ranged from 0.0 mg/kg to 0.031(0.02 mg/kg) and Chromium level was from 0.007 (0.01 mg/kg to 0.03). Similar variations were observed for different metals in liver and gills. Magnesium, Calcium, Zinc and Iron levels were the highest in this analysis for fish tissues. Two factor Anova showed significant variation in the mean metal concentration at 5% level of significance in September at Huruma and 20% level of significance for Ellingirini Dam in the same month. In February two factor Anova showed significant variation at 20%, 5% and 1% level at the same sampling points. The level of mean metal concentrations in the fish tissue and samples analysed were lower than the recommended WHO values. Discovery and Innovation Vol. 13 no. 3/4 December (2001) pp. 178-183 KEY WORDS: heavy metal pollutants, tissue concentration, environmental concern, depletion, industrial applications Résumé La présence de métaux lourds polluants dans les poissons pêchés du fleuve Sosiani, un petit fleuve qui traverse Eldoret, a fait objet d'une étude en février et septembre, 1995. Les métaux lourds étudiés étaient le cadmium, le chrome, le plomb, le zinc, le cuivre, le manganèse, le calcium, le magnésium. Tous ces métaux ont été détectés dans les tissus de poissons tels que muscles, branchies et foie, au moyen d'un spectrophotomètre d'absorption atomique. La concentration de divers métaux a varié pour différents tissus examinés. Par exemple dans les muscles, la concentration du cadmium est allée de 0,0 mg/kg à 0,031 (0,02 mg/kg), tandis que le chrome allait de 0,007(0.01 mg/kg) à 0,3 (0,02 mg/kg). Des variations similaires ont été observées pour différents métaux dans le foie et les branchies. Les concentrations du magnésium, du calcium, du zinc et du fer étaient les plus élevées dans les tissus examinés. L'ANOVA bi-factoriel a montré une variation significative dans la concentration moyenne de métaux, au seuil de 5% de signification, en septembre à Huruma, et 20% de signification pour le barrage d'Ellingirini, à la même époque. L'ANOVA bi-factoriel pour le mois de février a montré une variation significative au seuil de 20%, 5% et 1%, aux mêmes points d'échantillonnage. La concentration moyenne des métaux dans les tissus de poissons et autres échantillons analysés était inférieure aux normes recommandées par l'OMS. Discovery and Innovation Vol. 13 no. 3/4 December (2001) pp. 178-183 Mots-clés: métaux lourds polluants, concentration dans des tissus, problème environnemental, dégradation, traitements industriel

Yield Evaluation of Maize-Bean Intercropping in a Semi-Arid Region of South Africa

Information on the effect of row orientation on land productivity of intercropping systems, especially in a semi-arid environment is limited. Field trials were, therefore, carried out under full irrigation and rainfed conditions in a semi-arid region of South Africa (Bloemfontein, Free State) during 1998-2002. The trials evaluated the intercrop yield advantage in terms of land equivalent ratio (LER), energy value (EV) and monetary value (MV). Treatments included three cropping systems (sole maize, sole bean, and the intercrop) and two cultural practices, namely, row orientation (north-south row vs east-west row) and sowing date (November/December and January). Intercropping showed a higher yield advantage in terms of LER and EV compared to sole cropping. Therefore, intercropping has potential for increasing yields in the semi-arid regions of South Africa. Monetary value is influenced by fluctuations of the price ratio of crops, so it is not always a useful factor for evaluating the yield advantage.L'information sur l'effet de l'orientation en rangé sur la productive des terres des systèmes d'intercultures, spécialement dams un environnement semi-aride est limite. Les essais sur le terrain étaient par conséquent menés sous une irrigation complète et conditions de pluie dans une région semi-aride de l'Afrique du sud [Bloemfontein, /état libre] on cours de 1998-2002. Les essais évaluaient l'avantage de la production d'interculture en termes de proportion équivalente de terre [LER], la valeur d'énergie [EV] et la valeur monétaire [VM]. Les traitements avaient inclus trois systèmes de cultures [maïs seul, haricot seul et une combinaison maïs-haricot] et deux pratiques culturales, à savoir, l'orientation en rangé nord-sud contre rangé Est-ouest] et la date des semailles [Novembre/Décembre et Janvier]. L'inter-culture a monté un avantage supérieur en terme de LER et EV, comparer aux cultures seules. Par conséquent, les cultures en combinaison ont une potentialité d'augmenter les rendements en région semi-aride de L'Afrique du sud. La valeur monétaire est influencée par les fluctuations de la proportion des prix de récoltes, donc n'est pas toujours un facteur utile pour l'évaluation de l'avantage du rendement

Yield evaluation of maize-bean intercropping in a semi-arid region of South Africa

Information on the effect of row orientation on land productivity of intercropping systems, especially in a semi-arid environment is limited. Field trials were, therefore, carried out under full irrigation and rainfed conditions in a semi-arid region of South Africa (Bloemfontein, Free State) during 1998-2002. The trials evaluated the intercrop yield advantage in terms of land equivalent ratio (LER), energy value (EV) and monetary value (MV). Treatments included three cropping systems (sole maize, sole bean, and the intercrop) and two cultural practices, namely, row orientation (north-south row vs east-west row) and sowing date (November/December and January). Intercropping showed a higher yield advantage in terms of LER and EV compared to sole cropping. Therefore, intercropping has potential for increasing yields in the semi-arid regions of South Africa. Monetary value is influenced by fluctuations of the price ratio of crops, so it is not always a useful factor for evaluating the yield advantage. Key words: Land equivalent ratio, Phaseolus vulgaris, row orientation, Zea mays RÉSUMÉ L\'information sur l\'effet de l\'orientation en rangé sur la productive des terres des systèmes d\'intercultures, spécialement dams un environnement semi-aride est limite. Les essais sur le terrain étaient par conséquent menés sous une irrigation complète et conditions de pluie dans une région semi-aride de l\'Afrique du sud [Bloemfontein, /état libre] on cours de 1998-2002. Les essais évaluaient l\'avantage de la production d\'interculture en termes de proportion équivalente de terre [LER], la valeur d\'énergie [EV] et la valeur monétaire [VM]. Les traitements avaient inclus trois systèmes de cultures [maïs seul, haricot seul et une combinaison maïs-haricot] et deux pratiques culturales, à savoir, l\'orientation en rangé nord-sud contre rangé Est-ouest] et la date des semailles [Novembre/Décembre et Janvier]. L\'inter-culture a monté un avantage supérieur en terme de LER et EV, comparer aux cultures seules. Par conséquent, les cultures en combinaison ont une potentialité d'augmenter les rendements en région semi-aride de L\'Afrique du sud. La valeur monétaire est influencée par les fluctuations de la proportion des prix de récoltes, donc n\'est pas toujours un facteur utile pour l\'évaluation de l\'avantage du rendement. Mots clés: Proportion équivalente de terre, Phaseolus vulgaris, orientation en rangé, Zea mays African Crop Science Journal Vol.12(4) 2004: 351-35

A simulation model of cereal-legume intercropping systems for semi-arid regions II. Model application

Smallholder farmers in Africa practice traditional cropping techniques such as intercropping. Intercropping is thought to offer higher productivity and resource milisation than sole cropping. In this study, risk associated with maize-bean intercropping was evaluated by quantifying long-term yield in both intercropping and sole cropping in a semi-arid region of South Africa (Bloemfontein, Free State) with reference to rainfall variability. The crop simulation model was run with different cultural practices (planting date and plant density) for 52 summer crop growing seasons (1950/1951-2001/2002). Eighty-one scenarios, consisted of three levels of initial soil water, planting date, maize population, and bean population, were simulated. From the simulation outputs, the total land equivalent ratio (LER) was greater than one. The intercrop (equivalent to sole maize) had greater energy value (EV) than sole beans, and the intercrop (equivalent to sole beans) had greater monetary value (MV) than sole maize. From these results, it can be concluded that maize-bean intercropping is advantageous for this semi-arid region. Soil water at planting was the most important factor of all scenario factors, followed by planting date. Irrigation application at planting, November/December planting and high plant density of maize for EV and beans for MV can be one of the most effective cultural practices in the study region. With regard to rainfall variability, seasonal (October-April) rainfall positively affected EV and MV, but not LER. There was more intercrop production in La Nina years than in El Nino years. Thus, better cultural practices may be selected to maximize maize-bean intercrop yields for specific seasons in the semi-arid region based on the global seasonal outlook. (c) 2004 Elsevier B.V. All rights reserved

Determining Daily Radiation Interception in a Semiarid Inter-cropping System

Information on canopy radiation transmission is essential to understand energy balance in soil-plant-atmospherecontinuum, as net radiation is a major part of the energy balance. Compared with horizontally homogeneouscanopies, there could be large measurement errors in radiation transmission through heterogeneous canopies suchas row crops and inter-crops. In such canopies, the radiation transmission needs to be determined with greatcare. This study analysed the diurnal distribution of radiation transmission through maize and bean canopies inmono-cropping and inter-cropping using the data collected from field experiments in a semi-arid region of SouthAfrica, where solar radiation is not a limiting factor for plant growth. The results suggested that when the radiationtransmission is measured only at a given time, the measurement should be taken just before mid-morning (9:00–10:00) or mid-afternoon (14:00–15:00). This study further suggested feasibility of a simple rational model to estimatethe daily fraction of radiation intercepted by the canopies from the radiation interception measured at solar noon

A simulation model of cereal-legume intercropping systems for semi-arid regions I. Model development

Cereal-legume intercropping plays an important role in subsistence food production in developing countries, especially in situations of limited water resources. Crop simulation can be used to assess risk for intercrop productivity over time and space. In this study, a simple model for intercropping was developed for cereal and legume growth and yield, under semi-arid conditions. The model is based on radiation interception and use, and incorporates a water stress factor. Total dry matter and yield are functions of photosynthetically active radiation (PAR), the fraction of radiation intercepted and radiation use efficiency (RUE). One of two PAR sub-models was used to estimate PAR from solar radiation; either PAR is 50% of solar radiation or the ratio of PAR to solar radiation (PAR/SR) is a function of the clearness index (K-T). The fraction of radiation intercepted was calculated either based on Beer's Law with crop extinction coefficients (K) from field experiments or from previous reports. RUE was calculated as a function of available soil water to a depth of 900 mm (ASW). Either the soil water balance method or the decay curve approach was used to determine ASW. Thus, two alternatives for each of three factors, i.e., PAR/SR, K and ASW, were considered, giving eight possible models (2 methods x 3 factors). The model calibration and validation were carried out with maize-bean intercropping systems using data collected in a semi-arid region (Bloemfontein, Free State, South Africa) during seven growing seasons (1996/1997-2002/2003). The combination of PAR estimated from the clearness index, a crop extinction coefficient from the field experiment and the decay curve model gave the most reasonable and acceptable result. The intercrop model developed in this study is simple, so this modelling approach can be employed to develop other cereal-legume intercrop models for semi-arid regions. (c) 2004 Elsevier B.V. All rights reserved

Productivity of maize-bean intercropping in a semi-arid region of South Africa

Food shortage is known to have been caused by overpopulation, natural disasters and poor food distribution. In areas facing food insecurity, such as Africa, peasants or small-scale farmers have practised intercropping since old times. In this study, an investigation was carried out to determine whether intercropping increased production for small-scale farming in a semi-arid region (Free State, South Africa). Crop productivity of maize and bean intercropping systems was evaluated in terms of crop yield and growth. The effect of radiation and water utilisation by these systems was measured to determine their productivity. Field trials were carried out during three summer crop growing seasons (plant densities, row orientation and sowing date trials. In all growing seasons, rainfall was below normal, and air temperatures were normal. The total land equivalent ratios for yield and growth ranged between 1.06 to 1.58 and 1.38 to 1.86 respectively, showing yield and growth advantage of intercropping. Concerning radiation and water use, the intercropping of maize and beans had both radiation and water use efficiencies (RUE and WUE, respectively) as high as maize sole cropping, and intercropping RUE and WUE were greater than bean sole cropping. >From these results, it has been concluded that maize-bean intercropping can be recommended to small-scale farmers in this semi-arid region. Water SA Vol.29(4): 381-38

Food Poverty in Kisumu, Kenya

This chapter investigates the extent of food insecurity in Kisumu and examines the sources of food of the city’s residents. Seventy-one percent of sampled households in Kisumu were found to be moderately or severely food insecure with limited dietary diversity. The chapter argues, on the basis of the Lived Poverty Index findings present here, that food insecurity in Kisumu is an outcome of poverty, but that this poverty needs to be understood as multidimensional. The policy discourse around food security in Kisumu centres on encouraging food production to alleviate food insecurity. However, just 1% of households reported sourcing food from growing in Kisumu in the past year, and 3% from livestock owned by the household. The vast majority of food was sourced from market sources. These findings on food sources in conjunction with Lived Poverty Index findings suggest that the problem of food insecurity is systemic and requires responses beyond providing access to land and the promotion of urban agriculture