Salinization distribution

5.2. 1. 1 saline-alkali soil classification

Saline-alkali soil can be divided into three categories (trichotomy) according to its chemical composition, namely saline soil, alkaline soil (also known as non-saline soil) and saline-alkali soil.

(1) saline soil

Saline soil means that the soil contains enough soluble salt, which is harmful to the normal growth of crops. Soluble salts are mainly composed of cations Na+, Ca2+, Mg2+ and anions Cl-,.

(2) Alkaline soil

Alkaline soil refers to the soil that crops are affected by the existence of exchangeable sodium. This kind of soil contains high concentration of sum, which combines with Na+ in the soil to form sodium bicarbonate, which makes the pH value of the soil higher. It is a kind of soil that is more harmful to crops than saline soil.

(3) saline-alkali land

Saline-alkali soil refers to the soil that contains both excessive soluble salt and excessive exchangeable sodium. Saline-alkali soil has both salt and alkali hazards, so it can also be called saline-alkali soil.

According to the statistics of soil soluble salt analysis data, saline soil accounts for 84%, alkaline soil accounts for 10%, and saline-alkali soil accounts for 6%. Soil salinization in the Yellow River Delta can be divided into four grades:

Non-salinized soil: the total salt content is less than 0.2g/100g;

Mild saline-alkali soil: the total salt content is 0.2 ~ 0.4g/100g;

Moderate saline-alkali soil: the total salt content is 0.4 ~ 0.6g/100g;

Heavily salinized soil: the total salt content is more than 0.6g/ 100g.

5.2. 1.2 distribution law

The distribution of saline-alkali land is closely related to topography, showing certain regularity.

(1) Severe saline-alkali soil

Severe saline-alkali soil is mainly distributed in coastal lowlands and along the coastline, and its salinization degree tends to become lighter from the coastline to the inland; Secondly, it is distributed in Hejian Depression, such as Jixian Township-Fuwo Township and Gubei Reservoir-Sandaogou Reservoir in Lijin County.

(2) Moderately salinized soil

Moderate saline-alkali land is a transition zone from severe saline-alkali land to mild saline-alkali land around the distribution area, and the distribution area is small.

(3) Slightly salinized soil

Mild saline-alkali land is distributed in the gentle slope depression north of Xiaoqing River, with a wide distribution area.

(4) Non-salinized soil

Non-salinized soil is distributed in the piedmont alluvial-diluvial plain south of Xiaoqing River, the floodplain highland in the Yellow River levee, the ancient channel highland of the Yellow River, the top of modern Yellow River Delta and the top of crevasse fan. For example, 1976, the old course of the Yellow River and Hutan-Yihe River are non-saline soil areas, which are distributed in strips.