Vol. 1, No. 2, 1993

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    Detection of Seed- borne Fungi on Naturally Infected Seeds of Sesame
    (Faculty of Agriculture, University of Khartoum, Shambat, Sudan, 1993) Baghdadi, A.M. ; Salih, A.A.
    Inspection of dry seed samples of sesame collected from different parts of the Sudan showed that 72% of the seed samples contained dark black tiny sclerotia on the surface of the seeds. These were identified as the fungus Macrophomina phaseolina. Also, brown to grey discolouration of seeds was observed. A number of fungi were detected in untreated and pre-treated seeds by the blotter method. In untreated seeds, 13 seed-borne fungi were found. Alternaria sesami and M. phaseolina were detected in about 76% of the samples, while the percentage of other fungi was rather low. In pre-treated seeds, only 6 seed-borne fungi were encountered and the percentages of A. sesame and M. phaseolina were also high (72%). Other fungi showed small percentages of incidence in few samples. The results of untreated and pre-treated seeds indicate clearly that A. sesami and M. phaseolina are more common on sesame seeds than other fungi. The occurrence of Curvularia lunata and Drechslera tetramera in pre-treated seeds is a new record as seed-borne fungi in sesame.
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    Imprintation Interseeding. II. Seedling Growth and Biomass Production
    (Faculty of Agriculture, University of Khartoum, Shambat, Sudan, 1993) Abusuwar, A. O ; Dixon, R.M ; Schonhorst, M. H
    The effects of land imprintation on seedling growth and biomass production of some legumes and grasses interseeded into arid land ecosystem were studied at two experimental sites, namely Tucson and near Oracle, Arizona, from July 1983 to October 1985. The relative performance of grass, legume and grass- legume vegetative cover treatments were evaluated under four surface treatments (imprinted surface, mulched surface, imprinted-mulched surface and untreated reference surface). Transpiration rates and biomass production were significantly (P=0.05) higher on the imprinted than on the untreated surface. Lower leaf diffusive resistance was recorded on plants grown on imprinted surfaces reflecting the higher soil moisture under such surfaces. At Oracle, the imprinted surface increased biomass production by 102% over the untreated surface, and by 35% over the mulched surface. At Tucson, the increases in biomass production were 63% over the untreated surface and 33% over the mulched surface; however, mulching produced more biomass than the untreated surface. The relative growth of grasses and legumes in a mixture was influenced by seasonal factors. Grasses grew more rapidly than legumes in the fall, whereas the opposite was true in the summer. This seasonal growth pattern can benefit farmers and ranchers by distributing forage production more uniformly in time. These results suggest that land imprintation is an effective technique for increasing forage productivity in desert environments where precipitation is limited.
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    Construction of Volume Tables for Eucalyptus Plantations in Irrigated Schemes and Blue Nile Gerf Lands
    (Faculty of Agriculture, University of Khartoum, Shambat, Sudan, 1993) El Tayeb, A.M. ; El Siddig, E.A ; Erabi, E.B
    Volume tables were constructed for eucalypts plantations in the Gezira, El Rahad and El Suki irrigated schemes and the Blue Nile "Gerf" lands. Sample trees (564), covering the whole range of growth variation of Eucalyptus microtheca and E.camaldulensis, were used for this purpose. Volume equations were derived using regression techniques and statistical tests of fitness. Covariance analysis was used for comparing the equations constructed for the two species at different parts of the study area. A common volume table was constructed for E. camaldulensis plantations in the whole study area, but two different volume tables for E. microtheca were compiled one for the Gezira and another for El Rahad area. The differences in the volume equations parameters in those areas may be due to site factors and/or irrigation regimes.
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    Effects of Irrigation Intervals on Consumptive Use, Water Use Efficiency and Crop Coefficients of Sunflower
    (Faculty of Agriculture, University of Khartoum, Shambat, Sudan, 1993) Ahmed, M.F. ; El Naim, A. M
    Sunflower was grown for two successive seasons (1990/91 and 1991/92) at Shambat, Sudan (latitude 15°40 َN and longitude 32o32َ E) in a clay soil, montmorillonitic, with 48-54% clay, 25-29% silt, 17-25% sand and pH value of 7-8. The aim of the study was to investigate the effect of three irrigation intervals viz 7, 14 and 21 days on actual evapotranspiration (Et) as compared with estimated evapotranspiration using modified Penman formula and pan evaporation. Water use efficiency and crop factors were calculated. Prolonged watering interval, i.e., 21 days, led to decrease of water use efficiency, whereas the best water use efficiency was obtained under irrigation every seven days. Under all irrigation treatments, there was a large deviation of pan evaporation and modified Penman estimate from actually measured evapotranspiration. Pan evaporation was better correlated with the actually measured Et than modified Penman estimate. Crop coefficients were decreased with prolonging watering intervals, and with pan evaporation than with modified Penman formula in all irrigation treatments.