Composition Of Clay Minerals Of Red Soils From Different Parent Materials Under Long-term Fertilization And Modification Of The Related Minerals

Clay minerals are important components which determine soil structures and properties and therefore maintain the conditions of soil fertility.However,there are few information on the eff-ect of long-term application of fertilizers on the composition of clay minerals in red soils from different parent materials.Little is also known on the usage of these minerals in agriculture.In this paper,minerological methods were used to study the compostion of clay minerals in red soils from three parent materials at two long-term field experiment stations with treatments of different fertilizers.Three caly minerals related to red soil were purified and modificated to study their changes in micro-forms and specific surface area and their potentials to be used as additives in foliar fertilizers for tomato growth.Main results were gained as follows.1.Minerological identification and analysis showed that all red soils in this study contained three clay minerals,i.e.kaolinite,illite and vermiculite.However,the percentage of each of these minerals in a soil was controlled by the soil parent parent matirial.Illite took more than 70%of clay minerals in the soil from purple sandy rock;kaolinite took more than 80%of clay minerals in the soil from granite;and kaolinite took about 50%of clay minerals in the soil from Quaternary red earth.Different percentages of illite and vermiculite in the red soils from Quaternary red earth occurred at the two long-term experiment sites.2.Modification of purified kaolinite,illite and vermiculite by intercalation in laboratory conditions showed all the three minerals were povided increased interlayer distance,thinned layers and dicreased stack after the modification.The specific surface areas of the modified kaolinite,vermiculite and illite were increased by 14.7%,30.4%and 91.4%,respectively,as compared with their unmodified counterparts.3.Results of greenhouse pot experiment showed spraying 0.3%urea solutions containing 1%of modified kaolinite,illite or vermiculite on the base of conventional rates of fertilizer application significantly increased shoot hight,girth of stem,dry weights of above-ground and under-ground biomass of tomato grown in a paddy soil and a black soil.For example,the treatment with modified kaolinite increased above-ground biomass of tomato in the paddy soil by 68.4%and 31.1%as compared with the spraying water(control)and the spraying urea treatment,respectively.