Effect of Seeds source and Soil type on Seeds germination and Seedlings Establishment of Acacia polycantha (Willd) North Kordofan State, Sudan

This study was carried out during 2007/2008 in the nursery and experimental farm of Gum Arabic Research Center, University of Kordofan at El Obeid town, North Kordofan State, to study the effect of seed sources and soil types on seed germination and seedlings establishment of Acacia polycantha. Seeds were collected from three areas: South Darfur; South Kordofan and Blue Nile states. The study consisted of seed dormancy breakage test by several methods (pretreatment with soaking in cold and hot water, corroding by 25% and 50% conc. H2SO4, and itching by electrical needle); the seed were planted in the nursery in different soil types (sand, clay and mixture) and field establishment of the species through direct seed sowing and seedling transplantation. The seeds from South Darfur failed to germinate, and did not thrive satisfactorily both in the nursery and in the field, and thus were excluded from the experimentation. Seeds treated by electric needle test gave the highest germination percentage (60%). Treatment with H2SO4 25 gave the lowest values (20%), even (10%) x lesser than that of the control and cold water. The electric needle and the boiling water were effective treatment for Acacia polycantha seed dormancy breakage. The cold water and 50% conc. H2SO4 gave identical values. The seed source obviously had little effect on Acacia polycantha seed germination except for the control from Blue Nile which was twice stronger than that of South Kordofan. The study showed that there were significant differences among the types of soils in measured parameters in the nursery.The seedlings length in the mixture was better than in the sand. Little difference was observed between seedling length in the mixture and the clay, but the difference between the mixture and sand was about 1.5 folds. Root length growth in the sand showed better performance (32.1cm) and fallowed by clay and mixture. Shoot/root length ratio was similar in the clay and the mixture but that in the sand was the lowest. Seedlings of the mixture had denser foliage than those of clay and sand. Shoot dry weight was significantly different between the mixture and sand, while there was no difference between both mixture and clay and clay and sand. Seedlings in the sand had the lowest shoot masses.The shoot/root weight ratio, in the sand was far lower than that of clay and mixture; this difference exceeded 3.7 folds. xi For the seeds source, the Blue Nile seedlings length was higher than those of South Kordofan by a difference of 4.1 cm. Like wise a significant difference was obtained between the seedlings root length of the two locations; here the South Kordofan seedlings developed longer root lengths by a difference of 3.4 cm on average. The shoot/root length ratios of the seedlings of the two locations were 1.8 and 1.4 for Blue Nile and South Kordofan, respectively. For the shoot and root dry weights, the respective difference of magnitude in the mass values of these parameters was 0.7 and 0.8 g. For the shoot/root weight ratio, the Blue Nile seedlings were higher than those of South Kordofan, by a difference of 0.6. NPK and organic carbon content in the seedlings showed, no significant differences between South Kordofan and Blue Nile; also there were no significant difference between the soil type (Mixture and Sand) but the clay differed from the others in Potassium and organic carbon. Direct seed sowing in the field failed to germinate which was attributed to the poor sandy soil conditions and drought conditions. The study showed that there were no significant differences in the studied parameters for the seedlings transplanted in the field except for the root collar diameter; which was better in mixture fallowed by sand and clay. For the two seed sources there were no significant differences in diameter and xii number of leaves, but there were significant differences between them in seedlings length which was taller for Blue Nile than South Kordofan source. The study concluded that seed dormancy of Acacia polycantha can be easily broken by available pre-treatment methods, particularly hot water and electrical needle itching. Nursery seedling stock can be satisfactorily raised in sand-clay mixture soils. Seeds from different areas had different germination and growth rates which might be considered as separate provenances. Field establishment of Acacia polycantha in dry ecozones on sandy soils is very poor and better establishment may be obtained in more humid areas as on clay or loamy soils. In view of the scanty information about this species and envisaging its apparent potential as gum producing tree, more research work is needed both for natural stands and plantations