The past 15 years have been historically wet in many areas of the northern Plains. The result of this high rainfall period has been water tables moving closer to the soil surface. Having a water table too close to the soil surface results in water being wicked to the surface. When the water is evaporated away, the salts remain on the soil surface and accumulate over the years. Many farmers will call these “White Alkali” areas. One proven way to improve these salty soils is to lower the water table so that the salts cannot be wicked to the soil surface. Some ways to reduce salt accumulation at the soil surface include improving surface drainage, maximizing plant growth on the area and installing tile drainage.
In 2002, AGVISE established a demonstration project on a newly tile drained field. Our staff of Soil Scientists and agronomists thought it would be interesting to see how long it would take for the salt level in a tile drained field to be reduced enough to improve crop yields. 10 points were located by GPS in the tiled field demonstration site and the salt level has been tested at each GPS point for the past 10 years. The salt levels shown in the figure are for 2002, when the tile drainage was installed, 2006 and the fall of 2011. As you can see, the soluble salt level has greatly decreased in the many sites that tested higher than 1.0 mmhos/cm (1:1 method). Of course the sites that were relatively low in salts initially still have low salt levels. Yields have increased greatly on this field as the salinity levels have decreased. In particular, the soybean production on this field has improved. By lowering the soluble salt level in this field, the problem with iron chlorosis in soybeans is much less of an issue. While tile drainage is not the only answer to salinity problems, it is clear from this demonstration project, that tile drainage is a proven way to lower the soluble salt level in the soil and increase crop production over time.