Rwanda Journal of Agricultural Sciences

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RJAS Editorial Board — 2024-03-11

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Bioenergy perspective in Rwanda: The potential of the tree-based system in the agricultural landscape for fuelwood supply

E.N. Bapfakurera — 2024-03-11

Agriculture is the backbone of the Rwandan economy and employs more than 72.2% of Rwandans. Agricultural land is one of the scarcest resources, and its expansion leads to a decrease in forest areas and other natural resources. Studies on deforestation and forest degradation in Rwanda indicated that the reduction of forest areas has generally been due to the growing population leading to the expansion of agricultural land for food production and a high reliance on biomass as a cooking energy source. This review used different studies and reports to analyze the cause of fuelwood scarcity and the potential of tree-based systems in the agricultural landscape for fuelwood supply. The results indicated that biomass energy would likely remain the primary source of cooking energy, comprising 85% of Rwanda's energy for cooking. Given land scarcity and projected population growth in Rwanda, expanding forests for fuelwood is impossible. Therefore, the study underscores the imperative of integrating trees into the agricultural landscape to address fuelwood demand sustainably. Integrated trees in the agricultural landscape is a fruitful farming system in a land-scarce area to optimize land productivity, reduce pressure on forest areas by supplying fuelwood, and enhance the well-being of rural households by reducing the distance and time spent in fuelwood collection.

Current status of Cyprinids abundance and diversity and their potential for aquaculture production in Rwanda

R. Mwimba — 2024-03-11

The present study was conducted to get a recent overview of native and exotic cyprinid species in Rwandan waters, focusing on the abundance and the diversity and to identify those that may be used in Rwandan aquaculture industry. Seven hydrological areas were sampled during ten months in 2019-2020. Species identification was done by morphometrical analysis and using key guides. Eight cyprinid species were recorded. Lower Akagera was the most diversified area in cyprinid species (with H’=1.38±0.1 and D=0.29±0.0) and was significantly different (p˂0.05) compared to other hydrological areas. This area also showed higher fishes’ abundance. Beta diversity displayed higher similarity between Kigali water bodies and upper Akagera (SI=0.8), upper Akagera and Akanyaru (SI=0.667), upper Akagera and lower Akagera (SI=0.571). Dissimilarity was total; BCI=0.0 between northern lakes and Lake Kivu. Cyprinus carpio (RD=60.1±4.8, F=0.57±0.0) and Enteromius cercops (RD=18.1±2.0, F=0.43±0.0) were significantly dominant and frequent (p˂0.05) compared to other cyprinid species. Captures of common carps were significant and most of the specimens were of big size. Considering their total length and large body weight (TL=33.8±3.13cm, BW=3.0±2.12kg), the exotic species Cyprinus carpio revealed to be adapted to Rwandan ecological conditions and it can be used in the aquaculture industry throughout the country. In parallel, the native cyprinids Labeobarbus altianalis (TL=32.2±8.32cm, BW=2.5±1.86kg) and Labeo victorianus (TL=26.5±4.37cm, BW=0.5±0.12kg) were recorded with big size, they can also offer potentiality in aquaculture sector and further studies on induced spawning and adaptability in aquaculture of these cyprinid species are necessary.

Efficacy of storage treatments in delaying ripening in Avocados and reduce postharvest losses

B. Rwubatse — 2024-03-11

The present study investigated the ripening and senescence time, and the spoilage of avocados after ripening. Storage treatments used in the study included the open air, perforated and closed plastic sachets, Zero Energy Cooling Chamber (ZECC), and cold room. Avocados were harvested and brought to Postharvest Training Center at Mulindi, Rwanda. Nine (9) mature green avocados (Hass variety) without defects were selected for each treatment. The pulp temperature (ºC) and RH (%) of the storage package were recorded three times daily - morning (8:00), noon (12:00) and evening (16:00). Respective days to ripening and to senescence after ripening of avocados were - 11 and 5 in the open air, 8 and 8 in a perforated sachet, 9 and 7 in ZECC, and 22 and 8 in a cold room. The amount considered as a loss after ripening were - 56% in the open air, 33% in a perforated sachet, 22% in ZECC, and 11% in cold room. All Avocados in closed plastic sachets were rotted and were not attractive for consumption. Overall results showed that conservation of avocados in cold places with higher RH and ventilation can prolong their postharvest shelf life by delaying their ripening time and thus significantly reducing their postharvest losses.

Landslides Occurrence and Related Causal Factors in the Gishwati and Mukura Landscape of Rwanda

A. Fashaho — 2024-03-11

The Gishwati and Mukura Landscape of Rwanda was affected by and is still susceptible to landslides events. This research aimed to establish the relationship between landslides occurrence and some major related causal factors including precipitation, slope gradient, lithology, soil type and depth, and land use/ cover type. In total, 45 landslide locations with visible features were identified through field observation and survey. With the aim of contributing to the landslide hazard evaluation, a detailed analysis of the rainfall events from 1981 to 2017 was carried out on monthly basis. Other secondary data were also collected. The data recorded were analyzed and compared with the occurrence of landslides. The results revealed that heavy rainfall clustered during two rainy seasons were the principal triggering factor of landslides in the landscape. It has been revealed that 56.5% of the observed landslides falls into the slope category of 8.7 –27.5% followed by the category of 27.5–39.0% with 41.3% of the total case identified. The areas occupied by the crop land was found to be the most affected with 50.0% of the total identified sites, followed by forest (34.8%) and built-up areas (15.2%). The soils with high percentage of clay content (>35%), originated from granite and quartzite, dominate the identified zones that were affected by landslides. Based on these findings, the outcomes of this study will help to build short and long-term flexibility into landslide risk management planning processes and decisions at the Gishwati and Mukura landscape level.

Women's Participation in Climate Smart Agriculture (CSA) in Southeast, Nigeria

C.C. Apeh — 2024-03-11

Climate change (CC) impacts are complex, it affects ecosystems and crops growth and development. Farmers must understand its potential impacts on their crops and climate-smart measures that they can implore to be able to adapt such as the gender approach in the development of CSA policies. This study aimed at identifying the traditional CC adaptation information-sharing mechanisms and the CSA practices adopted by female farmers in Southeast, Nigeria. A well-structured questionnaire was used to collect data from 300 female farmers using a double huddle sampling technique. Data were analysed using descriptive statistics and a Likert scale method on a four- point Likert-type scale with a 2.5 decision point. Descriptive statistics result showed that most of the female farmers were young, with the mean average age of 28 years. The result of the Likert scale show that farmers relied on community leaders (mean=3.27), women groups (mean=2.68) and relatives (mean=4.05) for direction on immediate climate adaptive measures. It further identified high-yielding crop varieties (mean=3.06), crop diversification (mean=3.08), change in planting calendar (mean=2.96), fertilizers and manure application (mean=4.35), minimum/zero tillage (mean=3.06), cover cropping (mean=2.80), mulching (mean=3.18), fallowing (mean=2.81), mixed cropping (mean=2.74) and crop rotation (mean=2.54) as CSA practices used by farmers to enhance their yield and CC resilience. There is a need for CC solutions to start with the human dimensions in recognition of women as participants and contributors. Equally, CC should be tackled through a gender lens in defining, designing and implementing CSA activities that centre around: enhanced women's access and control of agricultural productive resources; equal access to information and services, and enhanced ability to innovate in response to evolving climate challenges and opportunities.

Review on Okra (Abelmoschus esculentus (L.) Moench) Production, Nutrition and Health Benefits

T. Uwiringiyimana — 2024-03-11

Okra is a nutritious vegetable crop with numerous health benefits. The consumption of adequate quantity and quality vegetables is vital for the proper functioning of the human body. A general review of okra was done to increase awareness of the cultivation and utilization of okra and undertake more research. The knowledge of climate, soil fertility, field management, and its health benefits helps to promote okra production and utilization. Okra is mainly cultivated in tropical and subtropical regions, especially in warm climates with annual rainfall and mean temperatures of 900-1,000mm and 18oC-35oC, respectively. Sandy or clay loam soils with a pH from 6.0 to 6.8 are recommended for okra cultivation. Generally, okra requires 150kg/Nitrogen, 112kg/Phosphorus, and 75kg/Potassium per hectare. Moreover, optimum growth, yield, and quality are obtained with proper plant population and mostly it is achieved with a spacing of 50cmx40cm. Pest and diseases like okra yellow vein mosaic virus, okra enation leaf curl virus, and fruit borers are the major production constraints; they cause yield losses and lower quality of the produce. Okra is nowadays known as food with healthy and medicinal benefits due to its composition. Okra leaves, pods, and seeds are edible and they are very nutritious. Okra leaves possess anti- inflammatory, anti-hyperglycemic, anti-hyperlipidemic, and antioxidant properties. This paper reviews okra in general from cultivation, climate requirements, field management practices, its health and nutritional benefits. Knowledge of proper field practices for okra cultivation and its health benefits will motivate farmers and actors in the agriculture and health sectors to promote okra cultivation and its consumption.

Relationship between farmers’ heterogeneity and adoption of fertilizers and hybrid seeds in Rwanda

J.D.D. Niyomugabo — 2024-03-11

The use of one size fits all model to deliver agricultural inputs to boost low crop yield is an alarming debate in Rwanda. This study was conducted in 17 districts distributed in three provinces of Rwanda to assess the one size fits all model use efficiency and develop key farm typologies. Similarly, by assessing Farm types’ characteristics that explain the uptake of agricultural production intensification options such as mineral fertilizers and hybrid seeds. Two-stage cluster sampling techniques were used to select randomly 2754 from 250000 families that worked with One Acre Fund and agro-dealers. Data were subjected to principal component analysis (PCA), a series of regression, and cluster analysis. The results reveal three main principal component (low, medium, and high adopters) associated with socioeconomic aspects. The cluster analysis reveals different ten clusters from 1 up to 10 equivalently farm types. The results show that farm types 1, 2, 3, 4 are low adopters and farm types 5, 6 and 7 are medium adopters while farm types 8, 9, 10 are high adopters of inputs. Farm types scattering between provinces are unevenly distributed (χ², p < .001). There is a significant discrepancy in adoption behavior across provinces, particularly farm types 2, 6, 8 and 10 which are uncommon in the Eastern but common in the Western Province. Farm type 7 is more common in the East and South regions than in the West region. Moreover, farmers' characteristics such as irrigation and agroforestry users and agricultural training receivers, affect significantly (p=0.01) fertilizers adoption and hybrids seeds. The current farm typologies should be applied nationally, and support programs tailored to them as one size does not fit all.

Chemotaxis and Ecology of Oviposition in Major Scarab Beetle Soil Pests of Crops – A review

A. Rutikanga — 2024-03-11

Anomala corpulenta, Holotrichia oblita, and Holotrichia parallela are scarab beetles and major soil-dwelling insect pests. Their larvae feed on roots of peanuts, soybean and potato, causing considerable yield loss (15-100%). Adults of Potosia brevitarsis are active above ground and feed on a range of fruits and sweet corn while its larvae feed on roots, dung and decaying matter. The pest status and management of these scarab beetles is a challenge to the farming community across the globe due to bans on soil insecticides, pesticide resistance, and limited efficacy of foliar insecticides. Understanding the chemical ecology of oviposition in these beetles is key to the development of alternative control strategies such as attract-and-kill traps. This review recorded 138 Volatile Organic Compounds (VOCs) from oviposition hosts of these beetles. These are green leaf volatiles, sex pheromones and odors from decomposing materials. These compounds are identified as terpenoids, aliphatic alcohols, esters, aldehydes, alkenes, alkanes, ketones, aromatic compounds, carboxylic acids, and heterocyclic compounds. They are also reported to bind on chemosensory receptors, which may justify oviposition behavioral responses in these beetles. Research gaps are highlighted to underpin the designing of further in-depth studies to develop selective and safer control measures for Integrated Pest Management programs.

Hydro-geological and meteorological behaviors of typical landslide prone hillslopes in North-western Rwanda

J. Uwihirwe — 2024-03-11

Landslide hazard prevention measures that include slope stabilization or an early warning system require an understanding of the hydro- geological and meteorological behaviors of the hillslopes prone to failures. This research aimed to understand the hydro-geological and meteorological processes and the relationship thereof using two typical hillslopes (Karago and Rwaza) that experienced slow moving rotational deformation. For each case study, geotechnical characterization and hydrological field and laboratory information was collected, i.e., saturated permeability measurements, soil moisture and groundwater monitoring. The surface displacements were also monitored and their linkage with hydrological processes was assessed. The geotechnical characterization indicated instability conditions (Fs<1) at the Karago hillslope and marginally stable conditions (1<Fs<2) at the Rwaza hillslope. The slope deformation and landslides occurred during the wettest conditions (i.e. soil moisture close to saturation and groundwater rises up to near surface). The surface displacements control points revealed the toe and head units to move faster than the intermediate units. The highest acceleration at the toe was attributed to the external incision agents like stream erosionwhile cracks and steeper failure plane were responsible for acceleration at the head units. The regression analysis indicated a strong correlation (R²=79%) between surface displacement and depth to groundwater and thus impactful for slope deformation and landslide initiation. The role of rainfall was also significant with long lasting low intensity rainfall being more important than short and high intensity rainfall.

Farmer Knowledge of Tagetes sp. and Its Potential Use as Alternative to Synthetic Insecticides for the Control of Maize Weevils in Rwanda

A. Rutikang — 2024-03-11

This study addresses storage pest challenges maize producers face in Rwanda, specifically Sitophilus zeamais. It aims to explore the potential of Marigold (Tagetes species) as a botanical pesticide for maize weevil control. The prevailing reliance on synthetic insecticides, which are costly and environmentally hazardous, necessitates alternative pest management strategies. The research involves two phases: a survey and bioassays. The survey evaluates the availability of pesticidal plants and farmer awareness regarding their use as botanical pesticides, emphasizing Marigold. Five districts (Rusizi, Muhanga, Gicumbi, Musanze, Gasabo, and Bugesera) are covered, with thirty farmers randomly selected from sectors within these districts. The survey assesses awareness of both pesticidal plants and maize weevils as pests. Bioassays are conducted in the University of Rwanda-College of Agriculture, Animal Sciences, and Veterinary Medicine laboratories, employing a Complete Randomized Design (CRD) with eight treatments and three replications. Maize grains infested with weevils are treated with varying doses of air-dried and ground Marigold biomass and positive control (Malathion). Over four weeks, weevil survival and grain damage are monitored every two days, alongside recording temperature and relative humidity. Survey results indicate the presence of pesticidal plants but low awareness (10%) of Marigold's potential as a botanical pesticide. Similarly, only 31% of farmers know maize weevils as pests. Bioassay findings reveal Marigold's comparatively lower effectiveness (40% and 53%) in contrast to Malathion (90%) for weevil control. Nonetheless, studies in Zimbabwe highlight Marigold's potential, achieving 100% weevil mortality after 56 days. While this study showcases Marigold's potential in achieving notable weevil reduction (40-53%), factors like humidity, temperature, dose, and bioassay duration may have influenced outcomes. Further investigations are recommended to encompass diverse climatic conditions, increased dosages, extended bioassay periods, and alternative formulations to validate Marigold's efficacy as a maize weevil control method in stored grains. This research signifies a significant step towards developing sustainable alternatives to synthetic insecticides for pest management in Rwandan maize production.

Effect of Imidacloprid Gaucho-Seed Coating on Mosaic Virus Transmission and the Dynamics of the Main Insect Pests of Common Bean (Phaseolus vulgaris L.) Cultivation in Rwanda

A. Karangwa — 2024-03-11

The common bean (Phaseolus vulgaris L.) is one of the principal food crops of Rwanda and Central Africa. It is cultivated by 92% of the family farms and constitutes the principal source of proteins for the majority of the Rwandan population. Since 2000, there has been a considerable decrease of the common bean yields and among the main causes are diseases and insect pests in particular the black aphid (Aphis fabae) vector of the Bean Common Mosaic Virus (BCMV), the bean stem maggots (Ophiomyia spp.), Cutworm (Agrotis segetum) and Bean leaf beetle (Cerotoma trifurcata). For contributing to the search of affordable methods and less polluting for the protection of common bean against insect pests, three doses of imidacloprid for seed coating (2g, 4g and 6g of active ingredient per kg of seeds) were tested and compared to the control (untreated) in a Completely Randomized Block Design (CRBD) with 5 replications in 2016B agricultural season. The overall objective of the trial was to protect the bean plants from insect attacks for the first eight (8) week period of young age when the plants are vulnerable to disease and insect attack.The imidacloprid seed coating has shown positive effect up to 8 weeks after the seed emergence; very few virus-infected plants (less than 3%) were recorded until 8 weeks after plant emergence; the percentage of infected plants increased up to 42% for the dose of 2 g of active ingredient per kilo of seeds and 25% and 23.5% maximum, respectively for the doses of 4 and 6 g of active ingredient per kilo. However, the symptoms of common mosaic appeared before the presence of wingless aphids on common bean plants. This suggests that winged forms of the black aphid stung the plants before the wingless forms of the black aphid settled. The used product has also controlled other insect pests, namely the bean stem maggots (Ophiomyia spp.), Cutworm (Agrotis segetum) and bean leaf beetle (Cerotoma trifurcata). In view of these results, we can recommend to bean producers, the coating of bean seeds at the dose of 6g of active ingredient per kilo of seeds to protect common bean plants against the mosaic virus and other insect pests.

Comparative study of nutrients and heavy metals in Rwandan macrophytes: Cyperus papyrus and Leersia hexandra

C. Kayirangwa — 2024-03-11

Macrophytes have been recommended to be naturally most efficient in water purification by fixing heavy metals and nutrients. This study aimed at comparing both nutrient and heavy metal contents in two Rwandan wetland plants, Cyperus papyrus and Leersia hexandra. Different plant parts and water samples were collected from Nyabugogo, Nyabarongo, Akanyaru and Akagera wetlands in Rwanda. Atomic Absorption Spectroscopy, Ultraviolet-Visible spectrophotometer and Flame Photometer were used to analyze the presence of heavy metals and nutrients. Results from the study revealed that Nitrogen was the most abundant nutrient in water with mean concentration of 9.160mg/mL, while Phosphorus was the least concentrated (0.160mg/mL) from all the sampling sites. However, the highest concentration of plant nutrients in leaves was Potassium (26.67mg/g). On the other side, the highest concentration of heavy metals in water was 40.2 mg/L for Fe in Nyabugogo site while its lowest concentration was found in Akanyaru with 10.05 mg/L. The highest concentration heavy metal in plant was Fe (2.699mg/g) while the least concentrated was Pb (0.060mg/g). This study showed that Leersia hexandra contains a high quantity of all heavy metals analyzed, therefore, a further investigation on Leersia hexandra should be conducted prior to being used as key material in phytoremediation.