Vol. 9, No. 2, 2001

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    Incidence of Fungi and Aflatoxins in Sudanese Faba Bean Seeds
    (Faculty of Agriculture, University of Khartoum, Shambat, Sudan, 2001) El-Nagerabi, S.E.A.F. ; Elshafi, A.E.E. ; Abdalla, A.H.
    Fifty six species and eight varieties belonging to 17 genera of fungi were isolated from the seeds of faba bean (Vicia faba L.). Among these isolates, 39 species and 5 varieties are considered new to the reported faba bean seeds mycoflora, whereas one genus and two species are new to the known mycoflora of the Sudan. The genus Aspergillus (13 species and 5 varieties) is leading among the prevalent genera followed by Rhizopus (3 species), Fusarium (5 species), Alternaria (6 species), Curvularia (6 species and one variety), Drechslera (2 species), Penicillium (5 species) and Emericella (4 species and 2 varieties), whereas the remaining 9 genera were encountered in a very low level of contamination. Of the serious pathogens of faba bean plants, Drechslera spicifera (2.16%), Fusarium oxysporum (3.35%) and Phoma herbarum (1.75%) were recovered from the seeds of this crop. Thin layer chromatographic analysis of chloroform extracts of 13 seed samples showed that two samples were naturally contaminated with aflatoxins B1, B2, G1 and G2 (10.5-23 μg/kg).
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    A Comparative Study of the Actually Applied and the Predicted Water Requirement for the Potato Crop (Solanum tuberosum) at Shambat, Sudan
    (Faculty of Agriculture, University of Khartoum, Shambat, Sudan, 2001) Hamad, E.E. ; Ali, A.M. ; Mohamed, A. E.E.
    This research was carried out in the Demonstration Farm of the Faculty of Agriculture, University of Khartoum, at Shambat, for the two winter seasons of 1992/93 and 1993/94.The study aimed at comparing the optimum quantity of irrigation water required by the potato crop per season and the predicted water requirement by using the modified Blaney-Criddle and Penman equations, based on the meteorological data at Shambat. To determine the optimum requirement of irrigation water, different amounts of water were applied in 1992/93 season (500, 600,700 and 800 mm per growing period) and in 1993/94 season (240, 320, 400, 480, 560 and 640 mm per growing period). Parshal Flume device was used to measure the applied water. Best stem emergence, haulm growth and total yield were obtained with irrigation water quantities ranging from 560 to 600 mm per season applied in 8-10 irrigations. The predicted seasonal water requirement, using Blaney-Criddle and Penman equations, were 450-491 and 475-524 mm, respectively. This means that the predicted water requirement is closer to the optimum range (560-600 mm) detected. Therefore, it is concluded that it would be more feasible to adopt Blaney- Criddle equation to predict the potato crop water requirement, specially under the semi-arid climates, because it is a function of easily measurable weather parameters compared to Penman method.
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    Effects of Watering Regimes on Growth, Yield and Quality of Potato (Solanum tuberosum) Under the Semi-arid Environment of Shambat, Sudan
    (Faculty of Agriculture, University of Khartoum, Shambat, Sudan, 2001) Ali, A.M. ; Hamad, E.E. ; Mohamed, A.E.
    An experiment was carried out in the Demonstration Farm of the Faculty of Agriculture, University of Khartoum, at Shambat, during the winter seasons of 1992/93 and 1993/94. The objective was to study the effects of irrigation water regimes on growth, yield and quality of the potato crop. Watering regimes used in the experiment were 500,600,700 and 800 mm per growing period in 1992/93 season and 240, 320, 400, 480, 560 and 640 mm per growing period in 1993/94 season. The Parshall Flume measuring device was used for the application of the required water regimes. The results showed that stem emergence was delayed by low water regimes. Vegetative growth and yield components responded positively to the increasing water regime up to 600 and 560 mm in 1992/93 and 1993/94, respectively. Highest (800 mm) and lowest (240 mm) watering regimes were associated with the lowest total and marketable yields. The highest yield of 17.9 tons/ha. was obtained by the watering regime 600 mm per season. Less water regimes (240­-500mm) were associated with low yield and high tuber infestation as a result of soil cracking and exposure of tubers to pests primarily potato tuber moth. It is concluded that the optimum irrigation water regime for the potato crop under Shambat environment ranges from 560 to 600 mm per season applied in 8 to 10 irrigations, depending on the prevailing climatic conditions.
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    Effects of Land Use on Soil Erosion by Rain and on the Loss of Some Soil Constituents in Al-Jabal Alakhdar, Libya
    (Faculty of Agriculture, University of Khartoum, Shambat, Sudan, 2001) Aburas, M.M. ; El-Mahi, Y.E. ; El-Doumi, F. M.
    The effects of land use on soil erosion by rain were studied in two locations in Al-Jabal Alakhdar, northeast of Libya. The first of these, Al-Hamama, lies at average slopes of 12%, and the second, Shahat, at average slopes of 9.35%. Each of the two locations was divided into three neighbouring parts. Each part consisted of three treatments with three replicates. The first was covered with forest trees, the second was cultivated with barley after deforestation, and the third was left fallow after forest removal. The experimental results showed that the largest soil and water losses occurred on the bare plots in both locations during the seasons 1995/1996 and 1996/1997. In Al-Hamama location, for example, soil losses amounted to 1.62 and 4.14 tons/ha, organic matter 51.7 and 139.8 kg/ha, total nitrogen 3.7 and 10.1 kg/ha and available phosphorus as little as 3 and 4 g/ha in the first and second seasons, respectively. In comparison, the losses from the barley cultivated plots were less, with soil losses of 0.219 and 0.046 tons/ha, and organic matter losses of 0.7 and 1.4 kg/ha in the first and second seasons, respectively. Only traces of total nitrogen and available phosphorus were lost from Al-Hamama barely cultivated soil in both seasons. On the other hand, practically no losses occurred in the forest-covered plots, characterized by significantly higher organic matter, water infiltration rates and aggregate stability. Losses from Shahat soil were much lower than those from Al-Hamama soil in both seasons.
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    Spatial Variation of Infiltration Rate and Related Soil Properties in a Central Gezira Clay Soil. II. Geostatistical Methods
    (Faculty of Agriculture, University of Khartoum, Shambat, Sudan, 2001) Mustafa, M.A. ; Ibrahim, A.S.A
    The spatial variation of steady-state infiltration rate (IR), clay content, ECe, CaCO3, SAR and pH (paste) at 5-m regular intervals, along two 500-m long transects (S-N, W-E) crossed in the middle were studied in two sites (Kubur and Talha) using geostatistical techniques. The data of the two transects were pooled for each site. An average and a 2-dimentional IR semi-variograms were computed for Kubur site. The former semi-variogram gave a better accountability to a spherical model than the latter. Thus, average semi-variograms were computed for all other soil properties. All average semi-variograms fitted the spherical model except that of clay content at Kubur site, which fitted a linear model. The parameters of the two models are provided and may be used in kriging. All semi-variograms exhibited nugget variances, indicating micro-scale spatial variability. The ranges for CaCO3, ECe, clay content, pH (paste), IR and SAR were 116, 58, 56, 53, 50 and 31 m, respectively. The cross semi-variogram for IR versus clay content, ECe, SAR, or CaCO3 are presented for both sites. The cross semi-variogram in Talha site showed that IR decreased with increase of clay content, and the relationship decreased with increase in lag distance. Other cross semi-variograms indicated lack of relationship between IR and the other soil properties.