In previous Blog posts, we discussed the potential issues with high salinity in irrigation water and soils and how to manage them. However, there is a specific salinity issue that turf managers dealing with fine-textured soils need to be aware of: sodium-induced soil deflocculation.
This scary-sounding term refers to the loss of soil structure that can be caused by high levels of sodium in fine-textured soils. This loss of structure can significantly reduce permeability and create headaches for turfgrass managers.
Note: High sodium levels are not a problem for turf managers dealing with sandy soils.
So, does your irrigation water contain a high enough concentration of sodium to cause soil deflocculation and a loss of soil structure?
You’ll only find the answer to this question by testing your irrigation water. On your water quality report, identify the SARw, adj SARw and adj RNa values.
If you are irrigating fine-textured soils with a pH of 7.0 or less, compare the ECw to SARw values in Table 1 to determine the likelihood of sodium cations in the irrigation water inducing soil deflocculation.
If you are irrigating fine textured soils with a pH greater than 7.0, compare ECw to adj SARw or adj RNa values in Table 1 (Click to enlarge).
As with all salinity issues, high sodium in your irrigation water doesn’t necessarily mean a problem is present in your soil. Your water test should serve only as an indicator. You’ll also have to test your soil.
To diagnose a potential sodium problem in your soil, locate the Exchangeable Sodium Percentage (ESP) value on your soil test report and compare it to the ESP Value ranges in Table 3 (Click to enlarge).
*Do not use sodium values reported in units of meq/L, this is not ESP. ESP is always reported on a percentage basis.
If your ESP is greater than 10% in an arid region or 15% in a non-arid region, you’ll need to take action to manage your high sodium issues.
You can learn more about this and other salinity issues by downloading our FREE Guide to Assessing and Managing Turfgrass Salinity Issues in Irrigation Water and Soils.