Saline, alkaline soils continue to pose problems for farmers

Posted Apr. 5th, 2013 by Barb Glen

Irrigation over-use | Salinity in southern Alberta a ‘significant agricultural concern’

PICTURE BUTTE, Alta. — Farmers often use the terms alkaline and saline interchangeably when de-scribing a fertility problem, says certified crop adviser Jack Feenstra. 

“Quite frankly, both are ugly.”

Both soil conditions reduce cropping productivity, and although there is a difference between the two, combating salinity is usually farmers’ focus.

“Alkaline refers to pH, which really doesn’t have much to do with the salt content, although it’s influenced by the type of salts,” said Alberta Agriculture land management specialist Rob Dunn.

“But having said that, when we’re talking about alkaline, we’re really talking about a gradient of salinity, from acidic to alkaline.”

Dunn and other salinity experts spoke at a March 19 meeting organized by the County of Lethbridge. Irrigation is widely available in the region and its over-use can increase saline conditions.

“Irrigation has wrecked a lot of land,” Feenstra said in a later interview. 

“Seeping canals, over-irrigation (and) in decades behind us, we had flood irrigation. All these things cumulated in land being destroyed. Salinity in southern Alberta, especially amongst irrigated parcels, is a significant agricultural concern.”

It’s a concern anywhere on the Prairies where salt has accumulated through water movement and evaporation.

Salinity refers to the concentration of soluble salts in soil, while alkalinity is a measure of pH, or hydrogen ions, said Dunn. 

Land that has never been broken tends to be pH neutral but once cultivated, it tends to become alkaline because of calcium and other salt pulled from the soil’s lower horizons.

However, Dunn said severely alkaline or sodic soil isn’t usually farmed because it doesn’t absorb water.

“Typically, for that reason, people were smart enough not to break them, but we do find these from time to time in some of our cultivated fields, and they can be managed.”

Electrical conductivity (EC) tests reveal the level of soil salinity, while alkalinity or sodicity of soil is gauged by testing the sodium adsorption ratio (SAR). EC and SAR values below two are considered most desirable for cropping.

A SAR value higher than four or five results in crop production problems, and if salinity is higher than two, “we’re starting to quite dramatically affect crops like beans and corn,” Dunn said.

“And even wheat will see some 10 percent yield reductions when you get above a salinity of about two or three.”