Understanding growth of East Africa highland banana: experiments and simulation

Key words: leaf area; radiation interception; QUEFTS model; fertilizer recovery fractions; nutrient mass fractions; crop growth; calibration; validation; radiation use efficiency; sensitivity analysis East Africa Highland banana yields on smallholder farms in the Great Lakes region are small (11−26 Mg ha−1 cycle−1 in Uganda, 21−43 Mg ha−1 cycle−1 in Burundi and 25−53 Mg ha−1 cycle−1 in Rwanda). The major causes of poor yields are declining soil fertility and soil moisture stress. In order to improve production, knowledge on highland banana physiology, growth patterns and response to fertilization is important, to establish the potential yield of the crop, to quantify the yield gaps between potential and actual yield, and to explore options for closing the yield gaps. Measurements of plant morphological characteristics, radiation interception and biomass (by destructive harvesting) were taken in experimental fields in central and southwest Uganda. Results showed that total leaf area can be estimated by using height and girth (used to estimate middle leaf area) and number of functional leaves. The light extinction coefficient, k determined from photosynthetically active radiation (PAR) measurements over the entire day was 0.7. Banana plants partitioned more dry matter (DM) to the leaves during first phase of vegetative growth, with the pseudostem becoming the dominant sink later with 58% of total DM at flowering, and the bunch at harvest with 53% of the total DM. Changes in dry matter partitioning influenced the allometric relationships between above-ground biomass (AGB in kg DM) and girth (cm), the relationship following a power function during the vegetative phase (AGB = 0.0001 (girth)2.35), and exponential functions at flowering (AGB = 0.325 e0.036 (girth)) and at harvest (AGB = 0.069 e0.068 (girth)). This thesis shows that allometric relationships can be derived and used to estimate biomass and bunch weights. In fertilizer trials, yield increases above the control (13.0 Mg ha−1 yr−1) ranged from 2.2−11.2 Mg ha−1 yr−1 at Kawanda, to more than double at Ntungamo, 7.0−29.5 Mg ha−1 yr−1 (control 7.9 Mg ha−1 yr−1). The limiting nutrients at both sites were in the order K>P>N. Differences in soil moisture availability and texture resulted in higher yields and total nutrient uptakes (K>N>P) at Ntungamo, compared with Kawanda. Per unit dry matter yield, highland bananas take up a similar amount of N (49.2 kg finger DM kg−1 N), half the amount of P (587 kg finger DM kg−1 P), and five times the amount of K (10.8 kg finger DM kg−1 K), when compared with cereal grain. Calibration results of the static nutrient response model QUEFTS using data from Ntungamo were fair (R2 = 0.57, RMSE = 648 kg ha−1). The calibrated QUEFTS model predicted yields well using data from Mbarara southwest Uganda (R2 = 0.68, RMSE = 562 kg ha−1). A new dynamic radiation and temperature-driven growth model, LINTUL BANANA 1 was developed to the compute potential yields of East Africa highland banana. The model considers (i) the physiology of the highland banana crop; (ii) the plant dynamics (i.e. three plant generations, Plant 1, 2 and 3 at different stages of growth constituting a mat); and (iii) three canopy levels formed by the leaves of the three plants. Average computed potential bunch dry and fresh matter were slightly higher at Ntungamo (20 Mg ha−1 DW; 111 Mg ha−1 FW), compared with Kawanda (18.25 Mg ha−1 DW; 100 Mg ha−1 FW), and values compared well with banana yields under optimal situations at comparable leaf area index values (20.3 Mg ha−1 DW; 113 Mg ha−1 FW). Sensitivity analysis was done to assess the effects of changes in parameters (light use efficiency, LUE; the light extinction coefficient, k; specific leaf area, SLA; the relative death rate of leaves, rd; relative growth rate of leaf area, RGRL; and the initial dry matter values) on bunch dry matter, leaf dry matter and leaf area index (L) at flowering. Sensitivity results for Kawanda and Ntungamo showed that changes in LUE1 resulted in more than proportional increase in bunch DM (1.30 and 1.36), a higher leaf DM (0.60 and 0.67) and L at flowering (0.60 and 0.67). Changes in rd1 values reduced bunch dry matter, leaf dry matter and L at flowering. Changes in SLA1 reduced only leaf DM, whereas both leaf DM and L at flowering were reduced by changes in k1 at both sites. Initial dry matter values had a small effect (sensitivity <br/

Towards sustainable Highland Banana production in Uganda: Opportunities and challenges

East Africa highland bananas (Musa sp., AAA-EAHB) are an important starchy food and cash crop in Uganda and the Great Lakes region of East Africa. Widespread reports of declining yields in Uganda since the 1930s and the low yields today do raise serious sustainability and food security concerns, especially as food demand increases with a population growth rate of 3.2% per annum. In addition, increasing urbanization continues to increase pressure on the banana systems, with bunches and leaves increasingly transported from rural areas to urban centres, leading to the continued loss of nutrients especially potassium. Actual yields on many smallholder banana farms (5−20 Mg ha−1 yr−1FW) in Uganda are far below the estimated potential yield (100 Mg ha−1 FW). Farmers cite soil fertility decline, pests (banana weevils and nematodes) and moisture stress as the major factors responsible for yield decline. In response, several organic and mineral fertilization experiments have been carried out at research stations and in farmers’ fields in Uganda since the 1950s. Researchers have mostly reported responses to organic fertilizers, no or poor responses to Mg and P fertilization with some responses to K and N fertilization, but with yields that are far below the estimated potential. Although pests are controlled in some trials, researchers have often failed to embrace a systems approach, quite often leaving out factors, such as moisture stress and soil physical conditions that affect the responses to fertilization. The government of Uganda in the National Development Plan 2010/11−2014/15 targets increased agricultural productivity for key staple crops like bananas in alleviating poverty in rural areas and ensuring national food security. In order to set proper banana research priorities to benefit farmers in Uganda, the objectives of this study were: to review past research aimed at reducing banana production constraints, identify opportunities and challenges facing the banana sector and put forward new research perspectives.Keywords: bananas, soil fertility, moisture, UgandaAfrican Journal of Food, Agriculture, Nutrition and Development, Volume 13 No. 2 April 201

SOIL CARBON AND NITROGEN STOCKS IN TRADITIONALLY MANAGED RANGELAND BIOMES IN KARAMOJA SUB-REGION, UGANDA

Rangelands are known for their potential in mitigating rising atmospheric carbon dioxide (CO2) concentrations in the world. The objective of this study was to investigate the patterns of soil organic carbon (SOC) and nitrogen (N) in rangelands under traditional management systems in Karamoja sub-region in Uganda, with a view to facilitating the development of appropriate and strategic management practices for the rangeland resources. The study was conducted during the wet season of the sub-region. Four land use/cover types (cropland, grassland, woodland and thickets/shrubland) were laid out in a completely randomised design. Soil samples were collected from four plots each one measuring 50 m x 40 m in each land use/cover type. A diagonal design was used for sample collection at depths of 0 - 15 and 15 - 30 cm. Results showed that at both soil depths, croplands had the lowest mean SOC and highest N; while grasslands had the highest SOC. Also, cropland recorded the highest mean soil bulk density at both depths. Based on soil analysis only, this study showed that conversion to cropland over a specified period of time can considerably reduce the ability of rangelands to sequester carbon. Further studies to include assessment of carbon stocks in the respective vegetation biomass are recommended.Les p\ue2turages sont connus pour leur potentiel d\u2019att\ue9nuation des concentrations croissantes de dioxyde de carbone (CO2) atmosph\ue9rique dans le monde. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9tudier les mod\ue8les de carbone organique du sol (COS) et d\u2019azote (N) dans les p\ue2turages sous les syst\ue8mes de gestion traditionnels dans la sous-r\ue9gion de Karamoja en Ouganda, en vue de faciliter le d\ue9veloppement de pratiques de gestion appropri\ue9es et strat\ue9giques pour les ressources des p\ue2turages. L\u2019\ue9tude a \ue9t\ue9 men\ue9e pendant la saison des pluies de la sous-r\ue9gion. Quatre types d\u2019utilisation/de couverture des terres (terres cultiv\ue9es, prairies, terres bois\ue9es et fourr\ue9s/arbustes) ont \ue9t\ue9 d\ue9finis dans un plan compl\ue8tement al\ue9atoire. Des \ue9chantillons de sol ont \ue9t\ue9 pr\ue9lev\ue9s dans quatre parcelles mesurant chacune 50 m x 40 m dans chaque type d\u2019utilisation/couverture des terres. Une conception diagonale a \ue9t\ue9 utilis\ue9e pour la collecte d\u2019\ue9chantillons \ue0 des profondeurs de 0 - 15 et 15 - 30 cm. Les r\ue9sultats ont montr\ue9 qu\u2019aux deux profondeurs du sol, les terres cultiv\ue9es avaient le COS moyen le plus bas et le N le plus \ue9lev\ue9 ; tandis que les prairies avaient le COS le plus \ue9lev\ue9. De plus, les terres cultiv\ue9es ont enregistr\ue9 la densit\ue9 apparente moyenne du sol la plus \ue9lev\ue9e aux deux profondeurs. Bas\ue9e uniquement sur l\u2019analyse des sols, cette \ue9tude a montr\ue9 que la conversion en terres cultiv\ue9es sur une p\ue9riode de temps sp\ue9cifi\ue9e peut r\ue9duire consid\ue9rablement la capacit\ue9 des terres des p\ue2turages \ue0 s\ue9questrer le carbone. D\u2019autres \ue9tudes pour inclure l\u2019\ue9valuation des stocks de carbone dans la biomasse v\ue9g\ue9tale respective sont recommand\ue9es

Canopy management, leaf fall and litter quality of dominant tree species in the banana agroforestry system in Uganda

Small-scale farmers in the banana-coffee agro-zone of Central Uganda plant andmaintain trees to provide a range of benefits. However, the impact of trees on soil fertility and crop yields is small. On many farms, trees exist in infinite numbers, compositions, with no proper spacing, sequencing and canopy management  recommendations. The objectives of this study were to: quantify and compare leaf fall and leaf litter biomass for the dominant tree species subjected to different pruning regimes and during different seasons and determine the nutrient  concentrations in leaf litter materials in order to assess their potential to improve soil fertility. A survey was conducted on 30 randomly selected farms to examine and  document the tree species. Four tree species were dominant; Ficus natalensis (15.3%), Albizia coriaria (10.2%), Artocarpus  heterophyllus (10.0%) and Mangifera indica (9.2%). Experiments such as canopy pruning, collecting leaf fall and weights of pruned leaf biomass were established for the four dominant trees on five randomly selected farms. A total of 120 trees were subjected to three pruning regimes (0%, 25% and 50%). Litter traps (1 m × 1 m) were placed 2 m from the tree trunk to collect falling leaves. Leaf biomass was collected from pruned branches and eighed. Leaf samples were collected from pruned leaves and a composite sample analysed for carbon and nutrient concentrations. Results showed that 40 tree and shrub species belonging to 21 families existed on farms. Leaf fall was highest in the dry season and A. Heterophyllus registered the highest amount. Leaf biomass from pruned trees was heaviest for M. indica (42.4 ±3 kg) in the wet season and at the 50% pruning regime (45.7± 2.1kg). Total  nutrient concentrations were in the order A. coriaria&gt;F. natalensis&gt;A.heterophyllus&gt;M.indica. We concluded that F. natalensis and A. Coriaria should be integrated more into the agroforestry system to improve soil fertility. A.heterophyllus and M.indica should be planted on farm boundaries. The 50% pruning regime was the best and should be carried out during the wet season.Key words: Tree species, canopy management, leaf fall, nutrient concentrations, soil fertilit

Farmers’ knowledge of the banana (Musa Sp.) agroforestry systems in Kiboga District, Central Uganda

Banana is a major food and cash crop in Uganda, particularly in the central and southwestern regions. However, production is still below attainable yields and at the same time declining due to a number of reasons, with low soil fertility being paramount. Few farmers use inorganic fertilizers, with majority of them relying mainly on organic supplements including integration of trees/shrubs. However, trees and shrubs exist on banana farms in undefined numbers and composition, with no spacing and canopy management recommendations. Also, there is limited information on farmers’ knowledge on these systems. A survey was, therefore, conducted on 70 randomly selected farms in Kiboga district, central Uganda to assess farmers’ knowledge of, as well as identify trees and shrubs species and banana cultivars in their agro-ecologies. A total of 1,558 trees and shrubs belonging to 40 species and 21 families were recorded in the study area (52 trees/shrubs per banana plantation). These were dominated by Jackfruit, Artocarpus heterophyllus (15%), Natal fig, Ficus natalensis (10%), Albizia, Albizia coriaria (10%) and mango, Mangifera indica (9%). Further, 1,779 banana mats belonging to nine (9) cultivars and three (3) genome groups were observed growing underneath these four commonest tree species (2.6 banana mats per tree). The highest number of banana mats was observed growing underneath F. natalensis (54%) and A. coriaria (42%). Most (87%) observed banana cultivars belonged to the cooking East African Highland Banana (Musa AAA-EAHB) and dominated by Ndibwabalangira (21%). Farmers reported 25 benefits they derive from banana-trees/shrubs integration; with shade and firewood (38%), as well as income and timber (35%) being the main benefits reported. They also reported that the highest percentage of benefits was derived from F. natalensis (44%) and A. coriaria (32%). Of the four (4) most prevalent tree species, A. coriaria (100%) and F. natalensis (96%) were reported as good companion plant to bananas, whereas, A. heterophyllus (99%) and M. indica (97%) were regarded as bad companion plants. Farmers preferred a tree that allows light penetration (96%), is compatible with bananas and other crops (87%) and has easily decomposable leaves (83%). Therefore, F. natalensis and A. coriaria should be integrated in banana agrosystems for soil fertility improvement whereas; A. heterophyllus and M. indica be planted on farm boundaries. However, the best-bet spacing and pruning regimes for these trees should be determined to minimize the negative attributes as much as possible.Keywords: Albizia coriaria, Artocarpus heterophyllus, banana cultivars, benefits, companions, Ficus natalensis, Mangifera indica, tree-specie

Sexual and reproductive health needs of adolescents perinatally infected with HIV in Uganda

In Uganda, HIV/AIDS treatment, care and support programs are still organized around either adult or pediatric care and fail to adequately address the needs of adolescents, specifically perinatally-infected adolescents. This study, implemented jointly by the Population Council\u27s Frontiers in Reproductive Health (FRONTIERS) program and the AIDS Support Organization (TASO), aimed to better understand the reproductive health and sexuality of this population group, and to identify anxieties or fears they have around entering social stages of adulthood. This study confirms that wide programmatic gaps exist in addressing the sexual and reproductive health needs of young people perinatally infected with HIV who are now growing into sexually active adolescents and adults

Canopy management, leaf fall and litter quality of dominant tree species in the banana agroforestry system in Uganda

Small-scale farmers in the banana-coffee agro-zone of Central Uganda plant andmaintain trees to provide a range of benefits. However, the impact of trees on soil fertility and crop yields is small. On many farms, trees exist in infinite numbers, compositions, with no proper spacing, sequencing and canopy management  recommendations. The objectives of this study were to: quantify and compare leaf fall and leaf litter biomass for the dominant tree species subjected to different pruning regimes and during different seasons and determine the nutrient  concentrations in leaf litter materials in order to assess their potential to improve soil fertility. A survey was conducted on 30 randomly selected farms to examine and  document the tree species. Four tree species were dominant; Ficus natalensis (15.3%), Albizia coriaria (10.2%), Artocarpus  heterophyllus (10.0%) and Mangifera indica (9.2%). Experiments such as canopy pruning, collecting leaf fall and weights of pruned leaf biomass were established for the four dominant trees on five randomly selected farms. A total of 120 trees were subjected to three pruning regimes (0%, 25% and 50%). Litter traps (1 m × 1 m) were placed 2 m from the tree trunk to collect falling leaves. Leaf biomass was collected from pruned branches and eighed. Leaf samples were collected from pruned leaves and a composite sample analysed for carbon and nutrient concentrations. Results showed that 40 tree and shrub species belonging to 21 families existed on farms. Leaf fall was highest in the dry season and A. Heterophyllus registered the highest amount. Leaf biomass from pruned trees was heaviest for M. indica (42.4 ±3 kg) in the wet season and at the 50% pruning regime (45.7± 2.1kg). Total  nutrient concentrations were in the order A. coriaria&gt;F. natalensis&gt;A.heterophyllus&gt;M.indica. We concluded that F. natalensis and A. Coriaria should be integrated more into the agroforestry system to improve soil fertility. A.heterophyllus and M.indica should be planted on farm boundaries. The 50% pruning regime was the best and should be carried out during the wet season.Key words: Tree species, canopy management, leaf fall, nutrient concentrations, soil fertilit

Deciphering the Complex Distribution of Human Immunodeficiency Virus Type 1 Subtypes among Different Cohorts in Northern Tanzania.

Increased understanding of the genetic diversity of HIV-1 is challenging but important in the development of an effective vaccine. We aimed to describe the distribution of HIV-1 subtypes in northern Tanzania among women enrolled in studies preparing for HIV-1 prevention trials (hospitality facility-worker cohorts), and among men and women in an open cohort demographic surveillance system (Kisesa cohort). The polymerase encompassing partial reverse transcriptase was sequenced and phylogenetic analysis performed and subtype determined. Questionnaires documented demographic data. We examined factors associated with subtype using multinomial logistic regression, adjusted for study, age, and sex. Among 140 individuals (125 women and 15 men), subtype A1 predominated (54, 39%), followed by C (46, 33%), D (25, 18%) and unique recombinant forms (URFs) (15, 11%). There was weak evidence to suggest different subtype frequencies by study (for example, 18% URFs in the Kisesa cohort versus 5-9% in the hospitality facility-worker cohorts; adjusted relative-risk ratio (aRR) = 2.35 [95% CI 0.59,9.32]; global p = 0.09). Compared to men, women were less likely to have subtype D versus A (aRR = 0.12 [95% CI 0.02,0.76]; global p = 0.05). There was a trend to suggest lower relative risk of subtype D compared to A with older age (aRR = 0.44 [95% CI 0.23,0.85] per 10 years; global p = 0.05). We observed multiple subtypes, confirming the complex genetic diversity of HIV-1 strains circulating in northern Tanzania, and found some differences between cohorts and by age and sex. This has important implications for vaccine design and development, providing opportunity to determine vaccine efficacy in diverse HIV-1 strains

HIV-1 pol Diversity among Female Bar and Hotel Workers in Northern Tanzania

A national ART program was launched in Tanzania in October 2004. Due to the existence of multiple HIV-1 subtypes and recombinant viruses co-circulating in Tanzania, it is important to monitor rates of drug resistance. The present study determined the prevalence of HIV-1 drug resistance mutations among ART-naive female bar and hotel workers, a high-risk population for HIV-1 infection in Moshi, Tanzania. A partial HIV-1 pol gene was analyzed by single-genome amplification and sequencing in 45 subjects (622 pol sequences total; median number of sequences per subject, 13; IQR 5–20) in samples collected in 2005. The prevalence of HIV-1 subtypes A1, C, and D, and inter-subtype recombinant viruses, was 36%, 29%, 9% and 27%, respectively. Thirteen different recombination patterns included D/A1/D, C/A1, A1/C/A1, A1/U/A1, C/U/A1, C/A1, U/D/U, D/A1/D, A1/C, A1/C, A2/C/A2, CRF10_CD/C/CRF10_CD and CRF35_AD/A1/CRF35_AD. CRF35_AD was identified in Tanzania for the first time. All recombinant viruses in this study were unique, suggesting ongoing recombination processes among circulating HIV-1 variants. The prevalence of multiple infections in this population was 16% (n = 7). Primary HIV-1 drug resistance mutations to RT inhibitors were identified in three (7%) subjects (K65R plus Y181C; N60D; and V106M). In some subjects, polymorphisms were observed at the RT positions 41, 69, 75, 98, 101, 179, 190, and 215. Secondary mutations associated with NNRTIs were observed at the RT positions 90 (7%) and 138 (6%). In the protease gene, three subjects (7%) had M46I/L mutations. All subjects in this study had HIV-1 subtype-specific natural polymorphisms at positions 36, 69, 89 and 93 that are associated with drug resistance in HIV-1 subtype B. These results suggested that HIV-1 drug resistance mutations and natural polymorphisms existed in this population before the initiation of the national ART program. With increasing use of ARV, these results highlight the importance of drug resistance monitoring in Tanzania

HIV Drug Resistance (HIVDR) in Antiretroviral Therapy-Naïve Patients in Tanzania Not Eligible for WHO Threshold HIVDR Survey Is Dramatically High

The World Health Organization (WHO) has recommended guidelines for a HIV drug resistance (HIVDR) survey for resource-limited countries. Eligibility criteria for patients include age below 25 years in order to focus on the prevalence of transmitted HIVDR (tHIVDR) in newly-infected individuals. Most of the participating sites across Africa have so far reported tHIVDR prevalences of below 5%. In this study we investigated whether the rate of HIVDR in patients <25 years is representative for HIVDR in the rest of the therapy-naïve population. HIVDR was determined in 88 sequentially enrolled ART-naïve patients from Mwanza, Tanzania (mean age 35.4 years). Twenty patients were aged <25 years and 68 patients were aged 25-63 years. The frequency of HIVDR in the study population was 14.8% (95%; CI 0.072-0.223) and independent of NVP-resistance induced by prevention of mother-to-child transmission programs. Patients >25 years had a significantly higher HIVDR frequency than younger patients (19.1%; 95% CI 0.095-0.28) versus 0%, P = 0.0344). In 2 out of the 16 patients with HIVDR we found traces of antiretrovirals (ARVs) in plasma. ART-naïve patients aged over 25 years exhibited significantly higher HIVDR than younger patients. Detection of traces of ARVs in individuals with HIVDR suggests that besides transmission, undisclosed misuse of ARVs may constitute a significant factor in the generation of the observed high HIVDR rate. The current WHO tHIVDR survey that is solely focused on the transmission of HIVDR and that excludes patients over 25 years of age may therefore result in substantial underestimation of the prevalence of HIVDR in the therapy-naïve population. Similar studies should be performed also in other areas to test whether the so far reported optimistic picture of low HIVDR prevalence in young individuals is really representative for the rest of the ART-naïve HIV-infected population