Increasing salinity (salts) has become a bigger problem in many areas the past 10-15 years. Excessive rainfall and poorly drained soils are a bad combination and the cause of salinity issues in our region. As the water table gets closer to the surface in wet years, water is wicked to the surface. Once the water evaporates, only the salt is left behind on the soil surface. Excessive salts reduce yields for many crops.
Surface drainage along with tile drainage and continuous cropping are the only way to reduce the salt level in soils over time. There are no magical soil amendments that will reduce the salt level in soil. When tile drainage is installed, the water table is lowered, which stops water from being wicked to the soil surface.
AGVISE has been monitoring the salinity (salts) of a tile drained field for a local grower since 2002. The grower was interested in seeing what happened to the salt levels in his field through the years. We established 10 points across the field and have collected 0-6″ and 6-24″ soil samples at each point after harvest each year.
In the figure you can see that over the past 10 years, the topsoil salinity has decreased significantly. The salinity was reduced, because the tile lowered the water table and excessive rainfall leached some of the salts down in the profile. The grower can now grow many different crops without losing yield to salinity.
In the past two years, this field has not received enough rainfall to leach any more salts from the soil. As you can see, the salt levels have actually gone up a little in the last year. In the future, we expect the salt levels in the soil will continue to decrease in years when rainfall is above average and water is drained from the field by the tile drainage system.