Saving of Irrigation Water in Arab Drylands

Bocharnikova, E.A.

Institute Physical-Chemical and Biological Problems in Soil Science.
Russian Academy of Sciences, Russia
e-mail: mswk@rambler.ru
 

Abstract

Water is a limiting factor for plant growth in the dry and semi-dry regions. Unfortunately, traditional irrigation technology doesn't prevent high losses (about 60-70%) of irrigation water because of leaching, evaporation, and transpiration through plants. The drop irrigation system allows reducing fresh water withdrawals by reducing water leaching, but doesn’t affect evaporation and transpiration levels. New technology for reduction of water irrigation application rate was elaborated and tested in laboratory and field experiments. The base of this technology is application of Si fertilizer with high content of active Si. Plants adsorb Si in the amounts exceeding that of other nutrients. Optimization of Si nutrition results in increased weight and volume of roots by 20 to 200% and enhanced drought and salt resistance of cultivated plants. Active Si compounds are shown to be extremely important for formation of soil fertility. They have a direct effect on soil texture and increase water-holding capacity by 20 to 30% and exchange capacity by 10 to 25%. We hypothesized that available also another mechanism: the adsorbed monosilicic acid in plants can transform to polysilicic acids and form silica-gel inside or outside of plant cells. The silica gel or polysilicic acid is hydrated silicon dioxide, which play role as rechargeable water tank. One atom of Si can attach up to 20 or more moleculesof water. By this means plant can storage water inside of the plant and to use it in the critical time.

Barley, wheat and grass were used in the greenhouse experiments and sorghum in the field demonstration, which were conducted on the sandy soils. Solid Si fertilizers were used and applied before seedling of tested plant. Water regimes in the greenhouse tests were used at 100, 80, 60 and 40% from optimal irrigation level. The active Si benefits for improving soil adsorption capacity (increasing from 20 to 40%) and water holding properties (increasing from 10 to 30%), increasing plant resistance to drought and salt toxicity. The greenhouse tests with different water regimes allowed determining the most effective sources of solid and liquid Si fertilizers, which could be used on commercial fields. The technology allows reducing irrigation water application rate by 20 to 50 % without negative influence on crop productivity and quality.

The field test was conducted on the 33 hectares of sandy soil. After seedling of sorghum the weather was extremely dry and during 6 months the rain was not come in. The field demonstration showed that application of commercial Si fertilizer completely safe all crop of sorghum against drought, while in the control plots all plants withered. The elaborated technology can be adapted for any soil-climatic conditions and quality of irrigation water. The elaborated technology has seven steps. The theoretical calculation of the effect of Si-based fertilizer application on the irrigated areas was calculated for Mediterranean countries.