In order to understand the extent of soil salinization in the Luohui Trench Irrigation District

63 soil samples and 71 groundwater samples were collected in situ in 2004.Soil salt content

degree of alkalization

anion and cation content

and chemical composition of groundwater were measured respectively.The present situation of soil salinization and the status of groundwater quality were analyzed.Results show that soil salinization in the irrigation district is considerably serious.Saline soils may be classified as the two categories of saline soil and alkali soil.The main salinity composition is consisted of sulfate of sodium(potassium)

calcium

and carbonate.The chemical characteristic of groundwater is in the category of sodium chloride-sodium sulfide

basically.It can be inferred that most of groundwater in the irrigation district has an adverse effect on irrigated crops according to its sodium adsorption ratio and magnesium coefficient calculated and has a threat of further alkalization to soil.Hence

an effective control of soil salinization is an important measure to control groundwater table in the irrigation district.Such factors as the concentrations of soluble salts of different districts and the salt-alkali tolerance of crops should be taken into account as well.It is suggested that the measures of engineering

biology

and chemistry should be combined to get twice the achievement with half the effort.