Invasive species in east Africa: current status for informed policy decisions and management

Invasive alien species are the second leading cause of biodiversity loss in the world today. A number of hypotheses have been advanced to explain the proliferation of invasive species. These hypotheses include deficiency of natural enemies in the introduced range, increased competitive ability, increased resource availability and emergence of more vigorous genotypes in the introduced range. In East Africa policy gaps that range from lack of information on invasive species management to how the available information is managed exist. Major gaps include, a deficiency in the number and interest of scientists studying invasion species biology, which subsequently leads to lack of interest in the learning institutions, severe deficiency in predictive and monitoring capacity, lack of coordinated control measures, and poor preparation in government departments. This report serves to identify the major gaps and provide information to assist in the prioritization and optimization of invasive species control and management. It recommends a need for scholars and institutions to develop curricula and recruit more scientists in this discipline. It also recommends an integrative approach, regional coordination and collaboration including sharing of information in an easy and practical language. The review further encourages the government and development agencies at the national and the local level to provide funding and incentives for low and localized programs to slow the spread of existing invasive species in order to protect the yet uninvaded ecosystems. The adaptation of these recommendations will result to control strategies and policy framework based on sound empirical information. It is expected that the report will be valuable for land, environmental managers and other stakeholders.Key words: Invasive species, East Africa, policy, managemen

Properties of Prosopis juliflora and its potential uses in Asal areas of Kenya

A study was done to determine the potential for processing and using Prosopis juliflora for commercial purpose. The effects of the plant on the soil were evaluated as a measure of determining its influence on the environment. Preliminary analysis of three soils samples per site where showed that the highly infested areas had higher moisture content of 10.5+1.35% and was significantly different at 5% level. The pH value of 8.7+1.03 was slightly lower compared to the low infested areas and was not significantly different at 5% level. However, both soils had almost the same bulk density and ECE of 1.1 g/cm3 and 0.03 dm/S respectively. The soil calcium content of 0.88+0.009 mg/l in the high density area was significant low at 5% level whereas the organic carbon content of 1.13+0.027% was significantly high. No significant difference was observed for the magnesium, sodium, potassium, organic matter and phosphorus content at 5% l. Plant samples of Prosopis juliflora were also tested for their nutritive values, especially the leaves, pods, bark and roots. Preliminary results showed that the leaves contain the highest amount of calcium of 6.38+0.248%. However, the leaves are not consumed green by the animals indicating high toxicity. The pods, bark and roots were also found to contain significant proportions of calcium at 5% level. The different parts of the plant had relatively lower phosphorus content of less than 0.25%. Magnesium was higher in the bark at about 3.5% whereas potassium was higher in the pods at about 2%. Nitrogen was higher in the leaves at about 2.5% indicating the suitability of the plant leaves as a nitrogen fixer in the soil. The tissues also showed very high content of vitamin C especially in the green pods (46.3+5.18 m/100g). Thus the pods, leaves and bark can be used as natural sources of vitamin C. The high ash content of 8.9+1.19% in the bark was significantly different at 5% level when compared to the content of the leaves but not other plant parts. This showed high roughage in the plant parts. The nutritive value of the pods showed their high potential for development of nutritive products including juice, wine, gum, powder, essential oils and beverages. The yield for aloe roots as fermenting agent was about 7.1% on 9th day in Prosopis extract having sugar media, 6.3% for yeast, Prosopis extract and honey on the sixth day and 6.1% for extract, sugar and baobab on the sixth day.Key words: Prosopis juliflora, properties, analysis, potential use

ENHANCING PRODUCTION THROUGH OPTIMISATION OF DPPH AND RADICAL SCAVENGING ACTIVITY OF GRAPE SEED EXTRACTS

Polyphenols are important for their pharmacological activity and positive contribution to cellular processes within the body. They have the capacity to protect against oxidation of High Density Lipids (HDL) and, thus help the body to retain HDL, while removing the problematic Low Density Lipids (LDL). Polyphenols also possess anti-ulcer, anti-carcinogenic and anti-mutagenic activities. The objective of this study was to evaluate the effect of temperature and grain size of grape seed on the efficiency of extraction of polyphenols from grape seed, using the compressed hot water and solvent extraction techniques. Polyphenols were extracted from milled (<0.5 mm) and whole grape seed, using compressed hot water (high temperature and high pressure) and solvents (Acetone, Methanol and Ethanol). The total polyphenol content and DPPH radical scavenging activity of the extracts were determined using spectrometer and the active compounds identified using HPLC. Total polyphenol content increased with extraction temperature, but decreased at 200 \ub0C. The difference in polyphenol extracts from the milled and whole seed decreased with increase in temperature, but was more evident at 135 \ub0C. The 2 hour extracts showed relatively higher values than those for 1 hour, with the lowest difference occurring at 165 \ub0C and the highest at 180 \ub0C. Solvent extracts from whole seeds were very low compared with the milled seeds, with acetone showing the highest value of 105 mg g-1 dry matter for polyphenol content and 110 mg g-1 of dry matter for DPPH radical scavenging activity. Methanol had the lowest value (78 mg g-1 dry matter) for polyphenol extracts and 80 mg g-1 for the DPPH radical scavenging activity. The main extract compounds were gallic acid, catechin and epicatechin.Les polyph\ue9nols sont importants eu \ue9gard \ue0 leur activit\ue9 pharmacologique et leur contribution positive aux processus cellulaires dans le corps. Ils sont dou\ue9s d\u2019une capacit\ue9 protective contre l\u2019oxydation des Lipides \ue0 Densit\ue9 Elev\ue9e (HDL) et, ainsi aident le corps \ue0 maintenir le HDL, tout en \ue9liminant les probl\ue9matiques Lipides \ue0 Basse Densit\ue9. Les polyph\ue9nols poss\ue8dent aussi des activit\ue9s anti-ulc\ue8res, anticarcinog\ue8nes et antimutag\ue8nes. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer les effets de la temp\ue9rature et taille des grains de raisin sur l\u2019efficacit\ue9 de l\u2019extraction des polyph\ue9nols des grains de raisin, utilisant une eau chaude compress\ue9e et des techniques d\u2019extraction au solvant. Les polyphenols \ue9taient extraits des grains entiers de raisin et des grains moulus (<0.5 mm) \ue0 l\u2019aide d\u2019une eau chaude compress\ue9e (temp\ue9rature \ue9lev\ue9e et haute pression) et des solvants (Ac\ue9tone, M\ue9thanol et Ethanol). La concentration totale des polyph\ue9nols et l\u2019activit\ue9 d\u2019absoption du radical DPPH des extraits \ue9taient d\ue9termin\ue9s \ue0 l\u2019aide du spectrophotom\ue8tre et les compos\ue9s actifs identifi\ue9s par HPLC. La concentration totale des polyph\ue9nols a augment\ue9 avec la temp\ue9rature d\u2019extraction, mais a diminu\ue9 \ue0 200 \ub0C. La diff\ue9rence dans les extraits de polyph\ue9nol des grains moulus et entiers a diminu\ue9 avec l\u2019augmentation de la temperature, mais \ue9tait plus \ue9vidente \ue0 135 \ub0C. Les extraits de deux heures ont montr\ue9 des valeurs relativement plus \ue9lev\ue9es que ceux d\u2019une heure, avec les diff\ue9rences les plus faibles apparaissant \ue0 165 \ub0C et les plus \ue9lev\ue9es \ue0 180 \ub0C. Les extraits de graines enti\ue8res aux solvants \ue9taient de faible quantit\ue9 en comparaison avec ceux des grains moulus, les valeurs les plus \ue9lev\ue9es \ue9tant de 105 mg g-1 de mati\ue8re s\ue8che de polyph\ue9nol et 110 mg g-1 de mati\ue8re s\ue8che d\u2019absorption du radical DPPH obtenues en utilisant l\u2019ac\ue9tone comme solvant. Les extraits obtenus au m\ue9thanol comme solvant \ue9taient encore en plus faible quantit\ue9 avec 78 mg-1 de la mati\ue8re s\ue8che pour les extraits du polyph\ue9nol et 80 mg g-1 pour l\u2019activit\ue9 d\u2019absorption du DPPH. Les principaux compos\ue9s de ces extraits \ue9taient des acides galliques, des cat\ue9chines et des epicat\ue9chines

Morphological diversity of Kenyan papaya germplasm

Papaya is one of the major fruit crops of the tropical regions of the world. It shows considerable phenotypic variation in morphological and horticultural traits that can be utilized in its genetic improvement. In Kenya, wide range of papaya germplasm exists and has not been characterized. Therefore, there is difficulty in differentiating the papaya accessions in the different regions of Kenya. Characterization of papaya germplasm is normally accomplished by use of morphological descriptors, hence as a first step, a germplasm collection from within Kenya was gathered and its morphological diversity was assessed. The papaya germplasm was collected from Coast, Nyanza, Western, Rift Valley, Eastern and Central provinces of Kenya and characterized in the field using morphological descriptors based on fruit, flower, stem and leaf characteristics. The morphological characters were recorded andmorphological data from sixty accessions were submitted to principal component and Neighbor- Joining cluster analysis. Accessions from Coastal, Western, Rift Valley and Nyanza provinces showed the widest morphological diversity with those from Eastern and Central provinces showing the least diversity. Fruit shape, fruit diameter, tree habit, leaf size and flower color showed the greatest variation in principal component analysis. The high diversity observed within the accessions points to ample possibilities of obtaining desirable trait combinations in specific cultivars.Keywords: Kenya, papaya, germplasm, morphological characterizatio

Effect of different rubber materials on husking dynamics of paddy rice

The conventional way to husk rice is to pass it between two rubber rollers that are rotating with a surface speed differential. The resulting normal pressure and shear stress causes the husk to be peeled away from the kernel. The process is suited to high-rice flow rates, but is energy intensive and can result in considerable wear to the surfaces of the rollers. The operating parameters for machines of this design are usually determined and set empirically. In this article, some experiments and calculations had been carried out in order to explore the mechanisms involved in husking rice grains using this method. A simple sliding friction rig with load cell and high-speed camera was used to observe the mechanisms that occur during husking. The husking performance of different rubbers was compared for changes in the applied normal load. It was found that grains rotate between the rubber counterfaces on initial motion before being husked. In addition, harder rubbers were found to husk a higher proportion of entrained grains at lower applied normal load. By measuring the coefficient of friction between rice and rubber samples, the shear force required to husk a given percentage of grains could be calculated and was shown to be constant regardless of rubber type. Based on the mechanism seen in the high-speed video, it was evident that there was a limiting shear stress that was the governing factor over the husked ratio

Effect of different rubber materials on husking dynamics of paddy rice

The conventional way to husk rice is to pass it between two rubber rollers that are rotating with a surface speed differential. The resulting normal pressure and shear stress causes the husk to be peeled away from the kernel. The process is suited to high-rice flow rates, but is energy intensive and can result in considerable wear to the surfaces of the rollers. The operating parameters for machines of this design are usually determined and set empirically. In this article, some experiments and calculations had been carried out in order to explore the mechanisms involved in husking rice grains using this method. A simple sliding friction rig with load cell and high-speed camera was used to observe the mechanisms that occur during husking. The husking performance of different rubbers was compared for changes in the applied normal load. It was found that grains rotate between the rubber counterfaces on initial motion before being husked. In addition, harder rubbers were found to husk a higher proportion of entrained grains at lower applied normal load. By measuring the coefficient of friction between rice and rubber samples, the shear force required to husk a given percentage of grains could be calculated and was shown to be constant regardless of rubber type. Based on the mechanism seen in the high-speed video, it was evident that there was a limiting shear stress that was the governing factor over the husked ratio

Simulation model for solar energy harnessing by the solar tunnel dryer

Models were developed to predict global solar radiation and the energy harnessed by a solar tunnel dryer, and simulated in Visual Basic 6.  In addition, the simulated data were compared with actual data.  Using a 10% absolute residual error interval, the developed model achieved 78.4% and 83.3% performance for global solar radiation and energy harnessing, respectively.  Further, the relationship between global solar radiation and the ten years mean satellite solar radiation, and that between the actual and simulated plenum chamber temperatures were linear, with coefficients of determination (R2) of 0.788 and 0.962.  Thus, it shows that there is the existence of strong correlation between satellite and predicted global solar radiation, and between predicted and actual plenum chamber temperatures.  Furthermore, Student’s t-test did not show any significant difference between simulated and actual data for solar radiation and energy harnessing.  Finally, this study shows that the developed model can be used to predict solar radiation and the energy harnessed by the solar tunnel dryer.Keywords: modeling, tunnel-dryer, global, direct, solar-radiation, plenum-temperature Citation: Kituu G. M., D. Shitanda, C. L. Kanali, J. T. Mailutha, C. K. Njoroge, J. K.Wainaina, and J. S Bongyereire. Simulation model for solar energy harnessing by the solar tunnel dryer.  Agric Eng Int: CIGR Journal, 2010, 12(1): 91-98

Heavy Metal Concentrations in Vegetables Cultivated and Sold in Machakos Municipality, Kenya

Heavy metal contamination of vegetables is a key aspect of food quality assurance since vegetables form a substantial proportion of the daily human diet. Health risks in urban populations due to exposure to heavy metals are on the increase because of the consumption of vegetables irrigated with wastewater. This study analyzed the concentration of Cd, Cu, Pb, Zn and Cr in spinach and kales grown using contaminated water of the Mitheu urban stream and those sold within Machakos municipality. Vegetable samples were collected once per month for a period of four months starting from June to September 2019. The mean heavy metal concentrations obtained were0.013 \u2013 3.19 mg/kg, 0.468 \u2013 1.706 mg/kg, 0.02 \u2013 0.368 mg/kg, 5.78 \u2013 26.7 mg/kg, and 0.104 \u2013 14.0 mg/kg for Cd, Cu, Pb, Zn and Cr respectively in kale samples from the different sampling sites. The heavy metal mean concentrations in spinach were 0.055 \u2013 0.575 mg/kg, 3.79 \u2013 5.55 mg/kg, 0.098 \u2013 1.49 mg/kg, 8.32 \u2013 20.7 mg/kg and 0.368 \u2013 4.43 mg/kg for Cd, Cu, Pb, Zn and Cr respectively. The mean concentrations of Cd, Pb, Zn and Cr in both spinach and kales in some of the sampling sites were above WHO permissible levels for heavy metals in vegetables for human consumption. However, the mean concentration of Cu was below WHO recommended levels. Consumption of these vegetables therefore poses a health risk to the consumers. There is need to create public awareness on the dangers of consuming contaminated vegetables. Additionally, measures to curb heavy metal pollution in Mitheu stream should be taken by the County Government of Machakos

Performance Analysis of Impellor and Rubber Roll Husker Using Different Varieties of Rice

Rosana G. Moreira, Editor-in-Chief; Texas A&M UniversityThis is a Technical article from International Commission of Agricultural Engineering (CIGR, Commission Internationale du Genie Rural) E-Journal Volume 3 (2001): D. Shitanda, Y. Nishiyama, and S. Koide. Performance Analysis of Impellor and Rubber Roll Husker Using Different Varieties of Rice. Vol. III, September 2001