Leveraging biological nitrogen fixation and soybean yield by planting duration under varying onset of rainy seasons in Uganda

Rainfall distribution and onset of rainy seasons, both of which are key determinants of the decision to plant most annual crops in sub-Saharan Africa (SSA), are increasingly difficult to predict due to climate change. Consequently, planting schedules affect both crops and vital natural systems such as biological nitrogen fixation in legumes. The objective of this study was to establish the optimum planting duration for soybean ( Glycine max L.), from the onset of the rainy season, in the context of nodulation and grain yield, and diversity of rhizobia in rhizosphere soil and nodules. A field experiment was set up with treatments, Bradyrhizobia inoculated and non- inoculated soybean variety Maksoy3N planted at four dates; 0, 10, 20 and 30 days from the onset of rain season. Diversity of rhizobia in the rhizosphere soil and nodules were fingerprinted using Single Strand Conformation Polymorphism (SSCP) method. Inoculation significantly (P<0.05) increased the number but not effectiveness of nodules and grain yield; which was attributed to presence of native strains in the soil. Planting after 10 days following the onset of a rainy season significantly (P<0.05) reduced grain yields and total yield loss was realised when seasonal cumulative rainfall was about 500 mm. Planting after 20 days from onset of rainy season significantly (P< 0.05) reduced the total number of nodules. A total of 8 and 12 clusters of bacteria from the soil and nodules at 5% dissimilarity, respectively, were recorded. The Bradyrhizobia species consisted of B. japonicum, B. japonicum (USDA 6), B. elkanii, B. liaoningense, B. canariense, and B. yuanmingense.La distribution des pluies et le d\ue9but des saisons pluvieuses, \ue0 la fois sont des d\ue9terminants cl\ue9s dans la d\ue9cision de semis de la plupart des cultures annuelles en Afrique sub-sahariennes (SSA), sont progressivement difficiles \ue0 pr\ue9dire \ue0 cause des changements climatiques. EN cons\ue9quence, le calendrier agricole affecte \ue0 la fois les cultures et les syst\ue8mes naturels vitaux tels que la fixation biologique d\u2019azote dans les l\ue9gumineuses. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9tablir la dur\ue9e optimale de culture pour le soja ( Glycine max L.), au d\ue9but de la saison pluvieuse, dans le contexte de la nodulation et du rendement en grain et la diversit\ue9 en rhizobia dans la rhizosph\ue8re du sol et les nodules. Une exp\ue9rimentation au champ a \ue9t\ue9 mise en place avec les traitements, la vari\ue9t\ue9 Maksoy3N inocul\ue9e et non inocul\ue9e avec Bradyrhizobia sem\ue9e en quatre dates\ua0; 0, 10, 20 et 30 jours depuis le d\ue9but de la saison. Les empreintes digitales de la diversit\ue9 de rhizobia dans la rhizosph\ue8re du sol et les nodules ont \ue9t\ue9 \ue9valu\ue9es en utilisant la m\ue9thode de recherche du polymorphisme de conformation (SSCP). L\u2019inoculation a significativement (P<0,05) fait augmenter le nombre mais non n\u2019effectivit\ue9 des nodules et le rendement en grain\ua0; qui est attribu\ue9e \ue0 la pr\ue9sence des souches natives au sol. Le semis 10 jours apr\ue8s le d\ue9but de la saison pluvieuse a significativement r\ue9duit (P< 0,05) r\ue9duit les rendements en grain et la perte totale du rendement a \ue9t\ue9 observ\ue9e lorsque la pluie cumulative saisonni\ue8re a \ue9t\ue9 environ 500mm. Le semis 20 jours apr\ue8s le d\ue9but de la saison pluvieuse a significativement (P< 0.05) r\ue9duit le nombre total de nodules. Un total de 8 et 12 groupes de bact\ue9ries du sol et des nodules \ue0 une dissimilarit\ue9 de 5%, respectivement ont \ue9t\ue9 observ\ue9s. Les esp\ue8ces de Bradyrhizobia sont consist\ue9 B. japonicum, B. japonicum (USDA 6), B. elkanii, B. liaoningense, B. canariense, et B. yuanmingense

Relative Suitability of Phosphorus Extraction Procedures for F Tropical Ferralsol

Purpose: To evaluate the predictive capacity common procedures for soil P extraction and testing in laboratories in the region. Materials and Methods: A pot study with treatments viz. soil phosphorus extraction methods (Bray I, Bray II and Mehlich 3), and six P application rates (0, 20, 40, 60, 80 and 100 kg P ha-1). Maize (Zea mays L.) variety Longe IV was the test crop. A Ferralsol from northwestern Uganda (West Nile) was used in this study. Results and Conclusion: Mehlich 3 correlated most with plant P uptake by presenting the highest correlation coefficient with plant P content (r = 0.254) and a number of leaves per plant (r = 0.733). A strong positive correlation existed between Bray I and Mehlich 3 extractable P values (r = 0.975), suggesting lack of a marked difference between them; implying that either of the two procedures could be applied for soil P extraction in Ferralsols. However, Mehlich 3, being a multi-nutrient extractant, was recommended as the most suitable for P extraction for the Ferralsol used in this study

A greenhouse experiment to evaluate compost derived from household and market crop wastes

No Abstract

Bioproductivity and Decomposition of Waterhyacinth in Uganda

The biological invasion of the waterhyacinth (Eichhornia crassipes (Mart.) Solms) into lakes and rivers of East Africa forced the implementation of mechanical harvesting around key harbours and dams, resulting in subsequent difficulties of waste disposal. Utilising these wastes assists in minising the costs of waste management. Estimates of waterhyacinth biomass were made by randomly deploying 1 m2 buoyant sampling frames across four sites on the Ugandan shores of Lake Victoria and determining the weight within the frame. Single plants ranging from 0.3 - 0.9 kg were placed within similar buoyant frames and their productivity monitored over a period of 16 weeks in a sheltered bay at Bugiri and a pond at Kajjansi. Nutrient contents and mineralisation patterns of harvested waterhyacinth wastes were characterised. Whole chopped plants and tissues were separated into leaves, petioles and roots, placed into litter bags, deployed as surface mulch and recovered over 16 weeks. Fresh biomass at the four sites was between 300 to 610 t ha-1. Productivity ranged from 58 to 228 t ha-1 yr-1 resulting from rapid production of daughter plants (108 to 237 plants m-2 yr-1). Decomposition of the waterhyacinth was rapid but with significant differences between plant tissues. Time to 50% decomposition of whole plants, leaves and roots was 21, 31 and 45 days, respectively. Waterhyacinth applied as surface mulch to fields may offer opportunity as an organic input to soils because of the relatively rich nutrient contents and rapid decay pattern but the large bulk of fresh plants (92% water) may offset these advantages.L\u2019invasion de l\u2019eau par la jacinthe (Eichhornia crassipes (Mart.) Solms) dans les lacs et rivi\ue8res de l\u2019Afrique de l\u2019Est a forc\ue9 l\u2019application des recoltes m\ue9caniques au tour d\u2019entr\ue9es importantes et de digues r\ue9sultant aux difficult\ue9s cons\ue9quentes des ordures. L\u2019utilisation de ces ordures aide \ue0 differer les co\ue9ts de contr\uf4le. Les estimations de la biomasse vivante ont \ue9t\ue9 faite al\ue9atoirement par des cadres flottables d\u20191m2 d\u2019\ue9chantillonnage dans 4 sites sur les rives du lac Victoria en Uganda et le poids des mauvaises herbes a \ue9t\ue9 d\ue9termin\ue9 \ue0 l\u2019interieur du cadre. Des plantes individuelles d\u2019environ 0.3-0.9 kg ont \ue9t\ue9 plac\ue9es \ue0 l\u2019int\ue9rieur de cadres semblables flottables et leur productivit\ue9 suivie pour une p\ue9riode de plus de 16 semaines sous l\u2019abri de baie \ue0 Bugiri et dans un \ueatang artificiel \ue0 Kajjansi. Le contenu nutritif et la tendance de min\ue9ralisation des d\ue9chets de la jacinthe recolt\ue9c ont \ue9t\ue9 caracteris\ue9s, toutes les plantes d\ue9coup\ue9es et tissus ont \ue9t\ue9 s\ue9par\ue9s en feuilles, p\ue9tioles et racines; plac\ue9es dans des sacs de d\ue9tritus \ue0 la surface comme fumier et r\ue9cuper\ue9 apr\ue8s 16 semaines. La biomasse fr\ue8che dans les 4 sites a \ue9t\ue9 estim\ue9e \ueatre de l\u2019ordre de 390 - 610 t ha-1. La productivit\ue9 variait de 58 - 228 t ha-1 yr-1 venant de la reproduction de 108 - 237 plantes ha-1 yr-1. Ces donn\ue9es sugg\ue8rent que la performance \ue9tait associe\ue9e aux differentes qualit\ue9s de syst\ue8mes aquatiques. La d\ue9composition de la jacinthe \ue9tait rapide mais avec de differences significatives entre les tissus des plantes. Le temps de d\ue9composition de 50% de toutes les plantes, feuilles et racines \ue9tait de21, 31 et 45 jours respectivement. La jacinthe utilis\ue9e comme paille de couverture en champs est avantageuse comme une resource organique aux sols \ue0 cause du contenu nutritif relativement riche et de sa d\ue9composition rapide

Bioproductivity and decomposition of waterhyacinth in Uganda

(African Crop Science Journal 1999 7(4): 433-440

Enhancing the Phytoremediation of Hydrocarbon-Contaminated Soils in the Sudd Wetlands, South Sudan, Using Organic Manure

Phytoremediation of hydrocarbon-contaminated soils is a challenging process. In an effort to enhance phytoremediation, soil was artificially contaminated with known concentration of light crude oil containing Total petroleum hydrocarbon (TPH) at a concentration of 75 gkg−1 soil. The contaminated soil was subjected to phytoremediation trial using four plant species (Oryza longistaminata, Sorghum arundinaceum, Tithonia diversifolia, and Hyparrhenia rufa) plus no plant used as control for natural attenuation. These phytoremediators were amended with concentrations (0, 5 and 10 gkg−1 soil) of organic manure (cow dung). Results at 120 days after planting, showed that application of manure at concentrations of 5 and 10 gkg−1 soil combined with an efficient phytoremediator can significantly enhance reduction of TPH compared to natural attenuation or use of either manure or a phytoremediator alone (p0.05). Therefore, the study concludes that use of phytoremediators and manure 5 gkg−1 soil could promote the restoration of TPH contaminated-soils in the Sudd region of South Sudan