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>F. natalensis>A.heterophyllus>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

Silicon pools, fluxes and the potential benefits of a silicon soil amendment in a nitrogen-enriched tidal marsh restoration

Tidal marshes are important sites of silicon (Si) transformation, where dissolved Si (DSi) taken up by macrophytic vegetation and algal species is converted to biogenic silica (BSi), which can accumulate in the soil, be recycled within the marsh, or be exported to adjacent coastal waters. The role of restored and created tidal marshes in these processes is not well understood, nor is the impact of nutrient enrichment at either the plant or ecosystem level. Here, Si fluxes were examined to develop a Si mass balance in a nitrogen (N)-enriched marsh created with fine-grained dredged material from the Chesapeake Bay, United States. In addition, the effectiveness of Si soil amendments to ameliorate the negative effects of excess nitrogen on Spartina alterniflora was examined through laboratory and field experiments. Silicon was exported to the estuary as DSi (49 g m−2 y−1) and BSi (35 g m−2y−1) in stoichiometric excess of nitrogen and phosphorus. Rapid recycling of Si within both marsh and the tidal creeks appeared to be important in the transformation of Si and export from the marsh. Enhanced macrophyte SiO2 tissue concentrations were observed in the field experiment, with end-of-season mean values of 2.20–2.69% SiO2 in controls and 2.49–3.24% SiO2 in amended plots, among the highest reported for S. alterniflora; however, improved plant fitness was not detected in either experiment. Thus, tidal marshes created with a fine-grained, N-rich dredged material appear to function as a rich source of Si to the restored marsh and local estuarine environment, an overlooked ecosystem service. Soil Si amendments, however, did not appear likely to alleviate N-induced stress in S. alterniflora

Seed degeneration of banana planting materials: strategies for improved farmer access to healthy seed

Vegetatively propagated crops suffer from yield loss and reduced stand density and longevity caused by the build‐up of certain pests and pathogens between successive plantings via infected planting material. Here, six seedborne phytosanitary problems of banana are reviewed to evaluate whether a seed degeneration framework is a useful tool to identify approaches to achieve healthier planting materials. Phytoparasitic nematodes and weevils generate gradual declines in yields and in sucker health. Fusarium wilt and banana bunchy top virus cause progressive mat collapse across the field. Symptomless suckers from any mat in infested fields represent a risk of transmitting the disease to a new field. Xanthomonas and ralstonia wilts, due to incomplete systemicity, are intermediate in their threat to yield loss and frequency of transmission in suckers. Losses to banana streak virus are triggered by abiotic stress, although sucker transmission of episomal banana streak virus also contributes. A qualitative equation described here for seed degeneration covers a cycle beginning with the quality and risk factors of the planting material used to plant a new field and ends with the quality and risk factors of the suckers extracted from the field to plant a new field. This review of five planting material multiplication methods commonly used in banana contrasts their differing usefulness to address seed degeneration in the small farm context. It is proposed that initiatives to offset banana seed degeneration should integrate the role of off‐farm actors into decentralized initiatives rather than attempt to duplicate national seed certification frameworks from other true seed or vegetatively propagated crops

Évaluation du potentiel prolifératif de six cultivars de bananier (cv. AAB, ABB, et AAA) par macropropagation en République Démocratique du Congo.

Objectifs: L’objectif était celui d’améliorer la technique de macropropagation pour la production du matériel végétal de plantation de bananiers, en comparant les différents cultivars en vue d’identifier le(s) cultivar(s) qui répond(ent) mieux à cette méthode. Méthodologie et résultats : Le test ELISA a été utilisé en vue de cribler les échantillons des plantes, en rapport avec la maladie de Bunchy Top (BBTD). Suivant le dispositif complètement randomisé avec trois répétitions dans les propagateurs, les résultats obtenus ont montré que le nombre total de plantules sevrées par explants le plus élevé a été observé chez les bananiers à cuire Saba et Cardaba respectivement avec 35 et 34 plantules, suivi du plantain Bubi avec 31 plantules. Tandis que, le nombre total de plantules le plus faible a été observé chez le Dessert Gros Michel avec 23 plantules. Conclusion et application des résultats: Au regard des résultats obtenus, tous ces cultivars peuvent être retenus et utilisés dans la technique de macro-propagation en vue d’augmenter la production de matériel de plantation de la culture de bananier en un temps record mais en mettant un accent particulier sur le plantain BUBI pour la ville de Kinshasa et ses environs. Ainsi, le fait que ces matériels biologiques testés soient indemnes de toute contamination virale (BBTV), ils constituent donc le matériel de choix en vue de leur macropropagation, étape préliminaire nécessaire à la mise en place d’un champ expérimental du système agroforestier

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>F. natalensis>A.heterophyllus>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

Super congruences and Euler numbers

Let $p>3$ be a prime. We prove that $$\sum_{k=0}^{p-1}\binom{2k}{k}/2^k=(-1)^{(p-1)/2}-p^2E_{p-3} (mod p^3),$$ $$\sum_{k=1}^{(p-1)/2}\binom{2k}{k}/k=(-1)^{(p+1)/2}8/3*pE_{p-3} (mod p^2),$$ $$\sum_{k=0}^{(p-1)/2}\binom{2k}{k}^2/16^k=(-1)^{(p-1)/2}+p^2E_{p-3} (mod p^3)$$, where E_0,E_1,E_2,... are Euler numbers. Our new approach is of combinatorial nature. We also formulate many conjectures concerning super congruences and relate most of them to Euler numbers or Bernoulli numbers. Motivated by our investigation of super congruences, we also raise a conjecture on 7 new series for $\pi^2$, $\pi^{-2}$ and the constant $K:=\sum_{k>0}(k/3)/k^2$ (with (-) the Jacobi symbol), two of which are $$\sum_{k=1}^\infty(10k-3)8^k/(k^3\binom{2k}{k}^2\binom{3k}{k})=\pi^2/2$$ and $$\sum_{k>0}(15k-4)(-27)^{k-1}/(k^3\binom{2k}{k}^2\binom{3k}k)=K.$

The contributions of biodiversity to the sustainable intensification of food production:Thematic Study to support the State of the World’s Biodiversity for Food and Agriculture

Biodiversity supports sustainable food production, although recognition of its roles has been relatively neglected in the sustainable intensification literature. In the current study, the roles of biodiversity in sustainable food production are considered, assessing how these roles can be measured, the current state of knowledge and opportunities for intervention. The trajectory of global food production, and the challenges and opportunities this presents for the roles of biodiversity in production, are also considered, as well as how biodiversitybased interventions fit within wider considerations for sustainable food systems. The positive interactions between a diverse array of organisms, including annual crops, animal pollinators, trees, micro-organisms, livestock and aquatic animals, support food production globally. To support these interactions, a range of interventions related to access to materials and practices are required. For annual crops, major interventions include breeding crops for more positive crop–crop interactions, and the integration of a wider range of crops into production systems. For animal pollinators, major interventions include the introduction of pollinator populations into production landscapes and the protection and improvement of pollinator habitat. For trees, a major required intervention is the greater integration of perennial legumes into farmland. For micro-organisms, the implementation of agronomic practices that support beneficial crop-microbe interactions is crucial. For livestock production, breed and crop feedstock diversification are essential, and the implementation of improved methods for manure incorporation into cropland. Finally, in the case of aquatic production, it is essential to support the wider adoption of multi-trophic production systems and to diversify crop- and animal-based feed resources. These and other interventions, and the research needs around them, are discussed. Looking to the future, understanding the drivers behind trends in food systems is essential for determining the options for biodiversity in supporting sustainable food production. The increased dominance of a narrow selection of foods globally indicates that efforts to more sustainably produce these foods are crucial. From a biodiversity perspective, this means placing a strong emphasis on breeding for resource use efficiency and adaptation to climate change. It also means challenging the dominance of these foods through focusing on productivity improvements for other crop, livestock and aquaculture species, so that they can compete successfully and find space within production systems. New biodiversity-based models that support food production need not only to be productive but to be profitable. Thus, as well as describing appropriate production system management practices that enhance production and support the environment, the labour, knowledge, time required to operationalize, and other costs of new production approaches, must be considered and minimized. To support the future roles of biodiversity in sustainable food production, we recommend that particular attention be given to the longitudinal analysis of food sectors to determine how the diversity of foods consumed from these sectors has changed over time. Analysis is already available for crops, but related research is needed for livestock and aquaculture sectors. This analysis will then support more optimal cross-sectoral interactions, in terms of the contributions each sector provides to supplying the different components of human diets. Additional meta-analyses and synthetic reviews of case studies are required as an evidence base for biodiversity-based food production system interventions, but future studies should pay more attention to articulating the potential biases in case study compilation (the problem of ‘cherry picking’ positive examples) and the measures that have been taken to minimize such effects