ProCrop 1999

WHERE DO SALTS ACCUMULATE?

It is common for potholes and slow moving natural drains to have a salt accumulation a short distance back from the water's edge. In this example, water can move laterally over a long period of time, flushing the soil of salts as it moves and concentrating these salts at the maximum depth above the water table where the capillary water rises and then evaporates. This condition is also common along road ditches, field ditches, and next to sewage lagoons.

Surface salt can accumulate due to seasonally wet soils. A feature found in seasonally wet saline soils is a relatively low area with white, crusty, salty material, surrounded with sparse crop growth and a sharp boundary where crops grow reasonably well. It is common when examining soil in these low areas to see pockets of crystalline salts in the plow layer. A subsoil sample beneath the fringe crop plants surrounding the bare area often reveals salt crystals there, also. However, crops in the depression edge usually grow normally. In this example, the crops root-ing into the capillary fringe have enough water, but, through drying of the soil around the roots, accumulate salts at the top of the capillary fringe, somewhere below the surface.

Salt conditions can occur in a subtly undulating landscape with a high soil clay content. This landscape usually would have an elevation difference of only 6 to 8 inches from top to bottom. Rainfall runs off the slowly permeable clay into the microrelief depressions in between the higher elevations. Water then leaches out the salts in the depressions. Groundwater containing salt rises through capillary flow to the highest soil surface.

In addition to these conditions, North Dakota also has large areas where a shallow water table lies under a relatively flat soil surface. Subsoil salt accumulation in these areas is wide spread. High rainfall years raise water table levels, which bring salts to or near the surface, adversely affecting crop growth. Following drought and a lower water table, rains leach the salts to a lower depth. As the salts are washed lower, the salt concentration in the rooting zone is decreased and crop growth benefits.

Back to Soils Menu
Back to Main ProCrop Index