Towards increasing and sustaining production of yam for food security and improved livelihoods in Uganda.
Yam (Dioscorea spp.) plays an important role in food security and is increasingly gaining importance as a source of income for smaller holder farmers in Uganda. However, the crop has not been given due attention in the national research and development (R&D) agenda in Uganda and nearly falls in the class of ‘neglected or orphaned crop’. The objective of this paper is to generate insights into the importance of yam in Uganda in order to increase production and improve food security. Primary and secondary information from studies conducted in Uganda show that the most popular yam types are the yellow varieties. Challenges include limited availability of yam, seed rendering it very expensive, high cost of staking materials and limited knowledge in yam agronomy and utilisation.
Nematode distribution and damage to yam in central and eastern Uganda
Yams (Dioscorea spp.) are food crops of growing significance in sub Saharan Africa. Unfortunately, nematodes are major pests to their production. A study was undertaken in major yam growing areas of Uganda to investigate the association of plant parasitic nematodes with damage symptoms. Nematodes were assessed from tubers, roots and surrounding soil for seven cultivars belonging to Dioscorea alata, D. bulbisiana, D. burkilliana and D. cayenensis at harvest. Pratylenchus sudanensis was found in the greatest density and was followed by Meloidogyne spp. Higher densities of both nematodes were observed in the tubers rather than roots. Although symptoms of cracking and galling were relatively low, P. sudanensis incidence was strongly associated with cracking and Meloidogyne spp. with galling. Pratylenchus sudanensis and Meloidogyne spp. incidence their associated damage were, however, negatively correlated, suggesting inter-species competition. Principal components analysis of data suggested that differences in susceptibility to P. sudanensis occur between yam cultivars and species.
Silica in Soils1
Publisher Summary Silica in free and combined forms is a dominant component of the solid material of many soils, and dissolved silica is commonly a major solute of soil solutions. Breakdown of primary silicates, translocation of silica in solution, and deposition of secondary silica-containing substances are involved in the development of soils. Ions essential for the growth of plants are released to the soil solution as silicates weather, and these ions may be held against leaching at exchange sites on other silicates. Silica is absorbed in appreciable quantities by some plants and is returned to the surface of the soil as the plants decay. The nature and transformations of silica and silicates in soil are, thus, fundamental to an understanding of many aspects of soil and plant sciences.