Experiments on the control of salinity and sodicity in surface-irrigated fields in the upper Yellow River valley (III). The state of salinization and alkalization in and around the Pingbu experimental field

In order to analyze the state of salinization and alkalization in and around an experimental irrigated field newly established in an alluvial valley of the Yellow Ricer, concentrations of ions contained in waters, soils and crops relevant to these phenomena were measured there. During the intensive surveys conducted in June, August and September 2007, the Yellow River water, irrigation canal water, groundwater, field soils and crops, etc. were sampled and their chemical characteristics such as electrical conductivity, pH, concentrations of ions Na⁺, Ca²⁺, Mg²⁺, K⁺, Cl ^-, SO₄^2- and NO₃^- were measured. The results obtained are summarized as follows: Irrigation seems to cause increases in the concentrations of ions Na⁺, Cl^- and SO₄^2- in the groundwater. Although those are also major ions contained in the field soil, the soil is classed as saline but not sodic according to the standard classification. On the other hand, Na⁺ is not concentrated in the crops because of their poor ability to absorb it. This seems to be one of the factors that cause salinization and alkalization of soil and water in irrigated fields. Therefore, cultivation techniques that use the ability of specific crops to absorb much Na⁺ and store it in shoots should be developed for effective and sustainable use of the irrigated field.