Soil Fertility Characterization in Mvumi and Mbogo - Komtonga Irrigation Schemes in Kilosa and Mvomero Districts, Morogoro Region, Tanzania.

Soil samples from three (3) mapping units in Mvumi and four (4) mapping units in Mbogo Komtonga representing two irrigation schemes in Kilosa and Mvomero Districts in eastern Tanzania were collected and analyzed for different mineral elements. Using zigzag sampling techniques, 9 composite samples with three replicates were collected at depth 0 – 30 cm from the delineated pedogeomorphic units at a radius of 20 m around the soil pits. Soil samples from each soil type were bulked, thoroughly mixed, sub sampled to obtain a representative composite sample, packed and sent to Mlingano National Soil Service laboratory (NSS), Tanga, Tanzania for the determination of physical chemical fertility indicators. The data showed overall significant (P ≤ 0.05) difference in fertility status in the selected irrigation schemes. The pH of top soils in Mvumi and Mbogo - Komtonga irrigation schemes ranged from 4.4 to 6.3. These were rated as extremely and/or strongly acid to slightly acid. Of the total area studied in Mvumi and Mbogo Komtonga irrigation schemes, 25.5 % is slightly acid, 40.2 % is medium acid, 31.0 % is extremely acid and 3.3 % extremely acid. Similarly, results of organic carbon (OC) determination from the top soil (0 - 30 cm) samples ranged from 26.6 g kg-1 to 51.8 g kg-1. This corresponds to 45.7 g kg-1 to 89.0 g kg-1 SOM in both irrigation schemes. The data showed that % OC in all irrigation schemes was very high in 92.2 % and high in 7.8 % of the surveyed areas. The results show that the top soils of all the surveyed areas in Mvumi and Mbogo - Komtonga irrigation schemes had N in the range of 1.2 to 3.8 mg kg-1, 48.7 % had N below the critical limits whereas 51.3 % were above the same. Available P in both schemes range from 0.68 – 6.53 mg kg-1. Based on the generally accepted threshold P level, all the observed P values in Mvumi and Mbogo - Komtonga respectively were considered to be below the critical range. Cation exchange capacity values in most topsoil in Mvumi and Mbogo - Komtonga irrigation schemes were rated as medium or high to very high. These values range between 27.0 – 54.6 cmol (+) kg-1 and were rated as medium in 25.5 %, high in 35.3 % and very high in 39.2 % of the total surveyed areas. Exchangeable Ca in the topsoil of Mvumi and Mbogo - Komtonga irrigation schemes ranged from 3.99 – 31.3 cmol (+) kg-1. These were rated as medium in 0.96 %, high in 34.3 % and very high in 70.2 %. Based on the critical limits, MV – Pa3 in Mvumi is likely to be deficient of Ca2+ for most crops as it lies below the proposed critical limits. Exchangeable Mg2+ in the irrigation schemes range from 0.28 – 5.07 cmol (+) kg-1, rated as high to very high. These data suggests that all the MUs except for MV – Pa3 in Mvumi and Mbogo - Komtonga have sufficient Mg2+ supplies for crop growth. Potassium in Mvumi and Mbogo – Komtonga irrigation schemes, range from 0.61 - 2.97 cmol (+) kg-1. These were rated as medium in 64.3 % to very high in 35.7 % of the total area. The data shows that in Mvumi K is unlikely to respond similar to Mbogo – Komtonga. The results of Naexch indicates that the levels of Na+ in the top soils corresponds to 0.15 – 0.47 cmol (+) kg-1 soil in both irrigation schemes. These values were rated as low in 16.4 % and medium in 83.6 % and the corresponding ESP range from 0.5 – 2.2 % in Mvumi considered non-sodic. These results suggest that the surveyed areas have no threat to sodicity problems and the major soil fertility constraints were soil reaction (pH), Nitrogen (N), Phosphorus (P) and poor Soil Organic Matter (SOM)

Can sub-Saharan Africa feed itself?

Although global food demand is expected to increase 60% by 2050 compared with 2005/2007, the rise will be much greater in sub-Saharan Africa (SSA). Indeed, SSA is the region at greatest food security risk because by 2050 its population will increase 2.5-fold and demand for cereals approximately triple, whereas current levels of cereal consumption already depend on substantial imports. At issue is whether SSA can meet this vast increase in cereal demand without greater reliance on cereal imports or major expansion of agricultural area and associated biodiversity loss and greenhouse gas emissions. Recent studies indicate that the global increase in food demand by 2050 can be met through closing the gap between current farm yield and yield potential on existing cropland. Here, however, we estimate it will not be feasible to meet future SSA cereal demand on existing production area by yield gap closure alone. Our agronomically robust yield gap analysis for 10 countries in SSA using location-specific data and a spatial upscaling approach reveals that, in addition to yield gap closure, other more complex and uncertain components of intensification are also needed, i.e., increasing cropping intensity (the number of crops grown per 12 mo on the same field) and sustainable expansion of irrigated production area. If intensification is not successful and massive cropland land expansion is to be avoided, SSA will depend much more on imports of cereals than it does today

The agronomic potential of vesicular-arbuscular mycorrhiza (VAM) in cereals – legume mixtures in Africa

Low yield currently experienced in mixed cereal-legume systems in Africa, is a manifestation of different biotic and abiotic constraints to crop production. These constraints include low availability of different soil mineral elements, toxicity due to heavy metals and hence tissue damage by reactive oxygen species, low N2-fixation from legumes, poor soil structure leading to low soil moisture availability, weeds, pests and diseases. However, mycorrhiza association involving cereal-legume mixed culture system may alleviate most of these constraints, thus, improving plant growth in crop mixtures. In this review, we report the agronomic potential of mycorrhiza association in cereal-legume mixed cultures

Effect of ecological factors on the accumulation of phenolic compounds in Iris species from Latvia, Lithuania and Ukraine

INTRODUCTION: It is important to conduct studies on the influence of environmental factors on the accumulation of secondary metabolites in plants, as well as the cultivation of plants and harvesting of their raw material. OBJECTIVE: In this study, we examined the influence of habitat types, soil composition, climatic factors and altitude on the content of phenolic compounds in Iris species from different populations in Latvia, Lithuania and Ukraine. METHODOLOGY: According to high-performance liquid chromatography (HPLC) analysis, 25 compounds (flavonoids, isoflavonoids, isoflavonoid glucosides, xanthones, phenolcarboxylic acids) were identified in the methanol extracts of 16 samples of Iris rhizomes. The quantitative data were further analysed by principal component analysis (PCA) to reveal the impact of environmental factors on the accumulation of compounds in plants. RESULTS: Iris pseudacorus from Latvia and Lithuania had a more diverse composition of phenolic compounds than samples from Ukraine. Sampled plants of the Iris subg. Iris had a higher content of the analysed compounds than those of Iris subg. Limniris. PCA results showed that the levels of phenolic compounds in Iris rhizomes were influenced by the content of soil nutrients. The phosphorus and potassium content had a significant impact on the levels of phenolic compounds, whereas the impact of nitrogen content was not significant. Meteorological factors had a small impact; however, sunshine duration had a significant positive effect and the amount of precipitation had a significant negative impact. CONCLUSION: The results of this study suggest that rhizomes of Iris species may be an important source of pharmacologically active compounds such as flavonoids, isoflavonoids and xanthones. Studies on the effect of environmental factors on the production and accumulation of secondary metabolites in Iris species are important because they contribute to knowledge of quantitative parameters [...]