New technologies for optimizing irrigation and increasing soil fertility in dry and semi-dry regions  Matichenkov V.V., Institute Basic Biological Problems Russian Academy of Sciences, Pushchino, Russia Bocharnikova E.A. Institute Physical-Chemical and Biological Problems in Soil Science Russian Academy of Sciences, Pushchino, Russia Abstract The technology for reduction of irrigation water application rate (from 20 up to 30%) without negative influence on the crop production and quality was elaborated. The basic of suggested technology is using of active Si for optimization of soil properties (water holding capacity, chemical composition) and plant resistance to water or salt stresses. The results obtained have demonstrated that the application of active Si increased soil water holding capacity by 10 to 30%, plant root system. Water holding capacity, adsorption capacity, and texture of the soil were optimized by active Si via the direct effect of monosilicic and polysilicic acids. The preliminary analysis for prospective of Si fertilizer application was conducted for several countries of Middle East.