Saturday, 15 July 2006

The Increase of Fertility and Productivity of Salt Affected and Poor Arid Soils by Using Biodiversity of Rhizobacteria.

Dilfuza Egamberdiyeva, Tashkent State Univ of Agriculture, University str. 1, Tashkent, 700140, Uzbekistan

Salinizaation of soils is a serious land-degradation problem in arid and semi-arid areas, and is increasing steadily in many parts of the world, causing major problems for crop productivity. Uzbekistan is an agroindustrial country, in which the desert occupies over 60% of all the republic's territory, and only 10% of the territory is taken up for agricultural lands. Cotton was the major crop produced in Uzbekistan for decades. Its production required an extensive use of chemical fertilizers and pesticides and was accompanied by strong irrigation of fields. This led to the drying up of the Aral Sea and resulted in strongly increased concentrations of chemical pesticides and natural salts. These substances were then blown from the increasingly exposed lake bed and contributed to desertification and water pollution from industrial wastes. Central Asia and neighbouring countries population suffered through the deep economic crisis affecting the coastal area the entire region. A shortage of water and its deteriorating quality have caused degradation of soil and vegetation in those areas, and irreparable losses in the fauna and flora. With respect to agriculture there are two main consequences of the crisis affecting agricultural production in the region: desertification of soils with excessive salinity and decreased fertility of over-intensively cultivated soils followed by increased salinity. Drought and salinity are the main stress processes of desertification, which strongly influence on and break of processing of many biological processes in soil living organisms. Plant productivity and yield in saline soils is considerably reduced due to improper nutrition of plants plus the osmotic and drought stress. Because plants are under saline or water unbalance stress, they become more vulnerable to diseases caused by pathogenic fungi. In such areas require intervention of biotechnology improving not only the crop but also soil productivity and health, the interactions of roots with its soil microoragnisms. Creation of association stress tolerant strains (resistant to drought, salinity, etc.) of rhizobacteria under different agricultural crops can lead to increase fertility of poor and salt affected soils of Aral Sea basin. Rhizobacteria help improve plant growth, nutrition, soil linked resistance to parasites, responses to external stress factors, and root growth pattern. This will positively affect emergence of seedlings in soils with a poor structure such as those in salinated soils of Uzbekistan. The aim the research work was to create of optimal composition of rhizosphere microorganisms, resistant to stress conditions, and study their effect on soil biological properties under various crops. Our results showed that bacterial inoculation increased soil enzyme activities, microbial populations in the rhizosphere, bulk soil and also stimulated plant growth and nutrient uptake of crop plants. Improvement of such plant microbe association in such environment will hopefully help improving cropping methods in arid lands, and help sustainable development by ensuring long term soil improvement.

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