Agro-ecological Zones Of Rwanda Research Articles

Diversity and composition of agroforestry species in two agro-ecological zones of Rwanda

This study delves into the diversity and composition of agroforestry species in Rwanda's Eastern Plateau and Eastern Savannah agro-ecological zones. Examining these systems across diverse landscapes is crucial for selecting species adapted to local conditions. We surveyed four landscapes with varying tree cover levels, using stratified random sampling to allocate 240 plots for detailed field inventory. We analyzed dendrometric characteristics of woody vegetation, focusing on plants with ≥ 4 cm diameter at breast height (DBH). Exotic tree species comprised over 75% of trees across all landscapes. Diversity indices indicated significant differences in plant communities between the Eastern Savannah and Eastern Plateau, with higher diversity in the former. Sørensen's similarity coefficient for woody species between the two regions showed a moderate level of similarity (approximately 53%). However, there was a significant difference in the equitability of on-farm tree species between the zones, suggesting non-identical distribution patterns. The most common and dominant tree species were Grevillea robusta, Mangifera indica, and Persea americana, primarily used for timber and fruit production. Most encountered trees were small and scattered, with nearly 80% having a DBH below 20 cm, highlighting the prevalence of young trees. The dominance of exotic species emphasizes the need for further research on their impact on agricultural biodiversity, informing sustainable land management practices in Rwanda and similar contexts.

Assessing the Adaptability of Quinoa and Millet in Two Agroecological Zones of Rwanda

Quinoa (Chenopodium quinoa Willd.) and millet species (including Eleusine coracana, Panicum miliaceum, and Setaria italica) are nutritionally valuable seed crops with versatile applications in food production and consumption. Both quinoa and millet have the potential to provide drought-tolerant, nutritious complementary crops to maize that is predominantly cultivated in Rwanda. This study evaluated quinoa and millet genotypes and assessed their agronomic performance in two agroecological zones of Rwanda. Twenty quinoa and fourteen millet cultivars were evaluated for grain yield, emergence, days to heading, flowering, and maturity, and plant height in 2016 and 2017 in Musanze, a highland region (2,254 m above sea level), and Kirehe, in the Eastern lowlands of Rwanda (1,478 m above sea level). Quinoa yield ranged from 189 to 1,855 kg/ha in Musanze and from 140 to 1,259 kg/ha in Kirehe. Millet yield ranged from 16 to 1,536 kg/ha in Musanze and from 21 to 159 kg/ha in Kirehe. Mean cultivar plant height was shorter in Kirehe (μ = 73 and 58 cm for quinoa and millets, respectively), than Musanze (μ = 93 and 76 cm for quinoa and millets, respectively). There was a genotype × environment interaction for maturity in quinoa and millet in both years. Across locations, “Titicaca” and “Earlybird” (Panicum miliaceum) were the earliest maturing quinoa and millet varieties, respectively, both with an average of 91 days to maturity. The results suggest that quinoa and millet have potential as regional crops for inclusion in the traditional dryland cropping rotations in Rwanda, thereby contributing to increased cropping system diversity and food security.

Variation of Yield and Chemical Composition of Essential Oil from Cupressus lusitanica Growing in Different Agro-ecological Zones of Rwanda

Chemical composition and essential oil contents among essential oil-bearing plants are mostly influenced by different factors including ecological features of habitat. In this study, variation in yield and chemical composition of essential oils (EOs) from the leaves of Cupressus lusitanica Mill. (Cupressaceae) in different regions of Rwanda was investigated. Extraction of essential oils from fresh leaves of C. lusitanica collected in March 2021 and April, 2021 from three different ecological zones of Rwanda, Buberuka highland zone (Burera), Central plateau zone (Huye) and Eastern savannah zone (Kayonza) was realized through steam distillation. The chemical compositions of distilled EOs were analyzed using both Fourier transform infrared (FT-IR) spectroscopy and gas chromatography-mass spectrometry (GC-MS), while their yields were determined by simple calculus. The average yields of the EOs were 0.27 ± 0.02, 0.34 ± 0.02 and 0.39 ± 0.01% (v/w) for Burera, Huye and Kayonza, respectively. Results of FT-IR analysis were confirmed by those of GC-MS analysis, and indicated the presence of different groups of compounds including aliphatic alkanes, carboxylic acids, alkenes, aldehydes, aromatics and ketones in the EOs. GC-MS results revealed that sabinene (20.84%), myrcene (19.63%), α-pinene (10.23%) and δ-3-carene (10.13%) were the dominant chemical constituents for EOs of C. lusitanica from Burera. Umbellulone (24.21%), δ-3-carene (16.76%), sabinene (10.54%) and α-pinene (8.21%) were the main constituents for EOs of C. lusitanica from Huye, while γ-terpinene (18.77%), umbellulone (18.16%), isobornyl acetate (9.972%), and myrcene (7.20%) were the major components of EOs of C. lusitanica from Kayonza. The current results demonstrated an intraspecific variation in content and chemical profile of C. lusitanica EOs from one geographical region to another. The observed variations are mostly due to the interactions of C. lusitanica species with climatic and environmental conditions of ecological habitat. However, it could also be the effects of various biotic factors, as well as maturity of plant and stage of plant growth. Further studies are needed to establish the influence of different geo-climatic and environmental factors on each single major component of C. lusitanica EOs.

Response of improved Brachiaria (Urochloa) grass cultivars to foliar diseases and their agronomic performances in Rwanda

Diseases have emerged as one of the major challenges of Brachiaria production in Africa. Nine Brachiaria cultivars were evaluated for leaf rust, leaf spot and leaf blight diseases and agronomic performances in two agro-ecological zones of Rwanda. The relationships between agronomic traits and area under diseases progress curve (AUDPC) were determined using Pearson correlation analysis. Cultivars differed significantly (p ≤ 0.05) for their response to these three diseases. Basilisk, Marandu, MG4, and Xaraes exhibited moderately resistant to resistant response to all three diseases, but Cayman and Cobra were susceptible to leaf rust. Site × cultivar × harvest interaction was significant for diseases and agronomic parameters (p ≤ 0.05). Cultivars also differed significantly for biomass production and dry matter content (p ≤ 0.05). The highest biomass producers were Marandu and Xaraes, and Cayman, Cobra and Piata had highest dry matter content. The AUDPC for leaf rust and leaf spot had negative and significant correlation with biomass yield. Our study concludes a satisfactory level of resistance in Basilisk, Marandu, MG4 and Xaraes to all three foliar disease in Rwanda. We recommend routine surveys for emerging and re-emerging Brachiaria diseases and studies to develop effective management measures against Brachiaria diseases.

Growth and yield performance of common bean (Phaseolus vulgaris L.) as influenced by plant density at Nyagatare, east Rwanda

Common bean (Phaseolus vulgaris L.) is one of the most important priority crops grown in Rwanda. It is utilized as a staple food and is consumed as edible seeds and pods for provision of proteins. Best agronomic practices that would promote its optimum growth and maximum yield should be recommended. Plant density affects productivity of common bean and optimizing it would increase light interception by the crop andminimize competition between plants, resulting into improved crop growth rate and yield. To determine the effect of plant density on common bean growth and yield, four different plant densities: 200,000, 250,000, 300,000, 350,000 plants/ha were investigated in a randomized complete block design, with three replications. Interaction effects between plant density with these parameters: plant height, plant biomass, number of pod per plant, 100grain weight and yield were assessed using analysis of variance (ANOVA). Results indicated that plant height was significantly affected by bean planting density (P<0.001), and was significantly higher in 350,000 plants ha-1 than for all other plant densities. Bean biomass was significantly affected by plant density (p=0.007) and was significantly higher in 250,000 plants ha-1. Bean planting density significantly affected the number of pods plant-1(P<0.001) and total bean yield (P<0.001). The number of pods plant-1 was highest at 249.5% using 200,000 plants ha-1 while 350,000 plants ha-1 density produced the lowest number of pods plant-1. Bean yield was significantly higher in 250,000 plants ha-1 and lowest in 350,000 plants ha-1. Hundred (100) grains weight was significantly affected by plant density (p<0.001). The highest 100 grains weight was found in 200,000 plant ha-1 while the lowest was found in 350,000 plants ha-1. These results indicate that 250,000 plants ha-1 population favors higher bean growth and grain yield. This study will provide an important basis to establish appropriate planting densities recommended for the bean crop in different agro-ecological zones of Rwanda. Key words: Common bean, plant density, plant growth, field performance, biomass, yield

Evaluation of Performance of Introduced Yam Bean (Pachyrhizus spp.) in Three Agro-Ecological Zones of Rwanda

The yam bean (Pachyrizhus spp) was recently introduced as a root crop with high-yield potential, considerable protein and micro-nutrient concentration to investigate its potential for food production in Rwanda. Except for Chuin types (Pachyrizhus tuberosus) which have high storage root dry matter (RDM) (26 to 36%), most accessions are consumed raw and are reported to have low RDM. The present study aimed to evaluate and identify adapted high yielding yam bean accessions in major agro-ecological zones of Rwanda. Field experiments with 22 accessions were conducted in 2012 at three research sites representing the major agro-ecologies of Rwanda. Strict reproductive pruning was followed to enhance fresh storage root yields. Across locations, ANOVA indicated highly significant differences (p < 0.01) for genotypes (G), locations (L), seasons (S) and G x L effects for storage root yield, vine yield and harvest index and accounted for 21.88%, 43.41%, 1.43% and 13.25% of the treatment sum of squares, respectively. The GGE bi-plot revealed that EC209018 is high yielding but unstable. However, genotypes, AC209034, AC209035 and EC209046, were outstanding in terms of adaptation and relative stability across the 3 locations, suggesting consistent root yields irrespective of location and environmental conditions. The GGE scatter plot showed that all genotypes formed one mega-environment for storage root yield (Karama, Musanze and Rubona) and two mega-environments for biomass yield (Karama and Rubona as one mega-environment and Musanze the second one). This study revealed that Karama is the most suitable environment for evaluation and selection of yam bean for yield components in Rwanda.

Self-Established Black Wattle Populations in Rwanda: Implications for Nature Conservation

Based on empirical evidence from a vegetation survey, this paper investigates the occurrence of self-established populations of black wattle (Acacia mearnsii De Wild.) in various environmental contexts and identifies areas where this species could be allowed to grow as a useful plant. The frequency of occurrence of self-established black wattle was found to be comparatively high above 1600 m of altitude. Three agro-ecological zones of Rwanda (Congo Nile Crest, Non-volcanic Highlands and Central Plateau) account for 70 % of the occurrence, most of which are inside tree plantations and woodlots and natural forests. In areas of most concern to black wattle invasion (especially in proximity of natural ecosystems), the following policy approach should be considered: eradication of current occurrences and a ban on the cultivation of this species. Elsewhere, control through utilization by local communities and adaptive management in areas least vulnerable to its invasion could suffice to keep this species under check.

Nutritional values of available ruminant feed resources in smallholder dairy farms in Rwanda.

Smallholder dairy farmers in Rwanda use diversity of resources to cope with endemic feed shortages. However, there is inadequate real farm data to support farmer decisions on choices of options. The main objective of this study was to evaluate nutritional quality of feed types that farmers use in different agro-ecological zones of Rwanda. Samples of feed types were collected from 90 randomly selected households in the low- and mid-high-altitude zones of Rwanda and analysed for proximate composition, contents of metabolisable energy (ME), organic matter digestibility (OMD) and neutral detergent fibre digestibility (NDFd). Rumen fermentation characteristics and efficiency of energy utilisation were examined by determining partitioning factor (PF). Results showed that only five out of 24 feed types were common in both districts. Chemical composition, OMD, ME, NDFd and PF of these feed types differed significantly (P < 0.05) in their nutritional attributes. This suggests that a common feed composition table can be used as a component of the decision support tool for rational feed resource development and utilisation in the smallholder farms in the selected agro-ecologies of Rwanda.

Resource use and food self-sufficiency at farm scale within two agro-ecological zones of Rwanda

Resource use and management are major determinants of the food self-sufficiency of smallholder farmers in sub-Saharan Africa. A study was conducted in Rwanda in two contrasting agro-ecological zones (Central plateau and Buberuka) to characterise farms, quantify their resource flows, and evaluate the effect of resource management on food self-sufficiency. The Simbi and Kageyo sectors were selected as the representatives of agro-ecological zones and two villages were selected within each sector. Wealth ranking, focus group discussions and formal survey techniques were used. Farms were classified into resource groups (RGs) that differed with regards to socio-economic and food self-sufficiency status. Soils were more fertile in Kageyo (Buberuka) than in Simbi (Central plateau). In both sites 67 % or more of the households were classified in the poorest category who cultivated less than 0.2 ha and experienced 4–5 months of food deficit each year. The partial N balance was more negative in Kageyo (−35.87 kg N ha−1 year−1) while the P balance was negative in close fields and outfields but positive in homefields (0.43 kg P ha−1 year−1). Calorie and protein availability were insufficient in RG1 (poor resource group) and RG2 (moderate resource group) farms in Simbi and RG1 (poor resource group) in Kageyo. Boundary line analysis indicated that poor soil C contents led to 0.6–0.8 t ha−1 less yield with respect to the attainable yield in better fields in RG 2. Closing the maize yield gap would result in doubling the energy and protein intake in Simbi. In such complex agricultural systems, there is a need to apply an integrated and multi-dimensional approach to understand differences among farms, identify limitations to food production and explore realistic options to ensure sustainable agricultural production and food self-sufficiency.

Comparison of Nutrient Composition and In vitro Digestion Characteristics of Four Forage Legumes from Two Agro-Ecological Zones of Rwanda

Comparison of Nutrient Composition and In vitro Digestion Characteristics of Four Forage Legumes from Two Agro-Ecological Zones of Rwanda

Comparison of Nutrient Composition and in vitro Digestion Characteristics of Four Forage Legumes from Two Agro-Ecological Zones of Rwanda

Comparison of Nutrient Composition and in vitro Digestion Characteristics of Four Forage Legumes from Two Agro-Ecological Zones of Rwanda

The sensitivity of PCR and serology in different Theileria parva epidemiological situations in Rwanda

Theileria parva is the causative agent of a lethal tick-borne disease of cattle occurring in eastern, central and southern Africa. Variations in the sensitivity of the serological and molecular tests with seasonal vector occurrence and discrepancies between low PCR prevalence and high T. parva vector density are a setback to estimate true prevalences. Therefore, the objectives of the present studies were to evaluate (1) the sensitivity of three serological tests (IFAT, ELISA and SELISA) and one molecular test (PCR) in the diagnosis of chronic T. parva infections in four different agro-ecological zones of Rwanda and (2) the effect of tick challenge and animal's age on the sensitivity of PCR. Blood samples from 635 bovines were collected in four agro-ecological zones of Rwanda. All sera were screened using the IFAT, ELISA, SELISA and PCR. The binary results of the four diagnostic tests were introduced separately for each agro-ecological zone in a Bayesian model to estimate the prevalence of T. parva infections and the sensitivity of the four diagnostic tests. All test specificities were set to 100%. The estimated T. parva prevalence was much higher (83–85%) than estimations based on single diagnostic tests. The estimated sensitivity of serological tests was relatively constant and ranged from 57 to 75% in the various areas. The sensitivity of PCR showed more pronounced variations, ranging from 66% in the low T. parva transmission (high land) zones compared to 24% in the highly vector infested (low land) zones. Calves and adult cattle ( n = 194) were also sampled in regularly and irregularly dipped herds in the low land region. The apparent T. parva prevalence detected by PCR was significantly higher in calves than in adult cattle and in herds regularly treated with acaricides, while no significant differences were found with IFAT. The conditional probability that a sample was positive at PCR while it was positive at IFAT was significantly lower in adults. The implication of these findings in the use of diagnostic assays for epidemiological studies is discussed.

Radon diffusion through thin plastics

Soil nutrient depletion is one of the major causes of high yield gaps and nutrient deficiencies in East Africa highlands, including Rwanda. This research sought to determine the current soil nutrient balance and its spatial variation in 10 Rwandan agro-ecological zones. Soil nitrogen (N), phosphorus (P) and potassium (K) depletion in croplands were calculated using data from 455 field trials of the Optimizing Fertilizer Recommendations in Africa (OFRA) project in Rwanda. Calculated soil nutrient balances (NPK) and 15 environmental covariates were used to calibrate soil nutrient depletion models using ensemble machine learning (EML) and 10-fold cross-validation. In the 2019–2020 growing season, annual N and K depletions were 33.6 kg N ha−1 yr−1 and 71.0 kg K ha−1 yr−1, with a positive P balance of 2.30 kg P ha−1 yr−1. High soil nutrient uptake and high soil nutrient loss due to erosion and leaching were two main causes of NPK depletion. Spatial variations of NPK balance were influenced by soil nutrient stocks, soil erosion, elevation, rainfall, soil texture, and soil bulk density. The 10-fold cross-validation showed that coefficients of determination (R2) of NPK models were 62%, 58%, and 58%, respectively. Compared to single models, ensemble machine learning improved NPK model accuracy up to 5%. Our research revealed that soil nutrient depletion was highest in the northwest and lowest in the southeast of the study area. We conclude that increasing soil nutrient inputs without reducing soil nutrient loss due to soil degradation will not decrease soil nutrient depletion in Rwanda and ensemble machine learning outperforms single models in predicting soil nutrient balance. The solution to reduce high soil nutrient depletion in all agro-ecological zones of Rwanda would be to prioritize soil and water conservation measures and increase soil nutrient inputs.