Salt Map FAQ
Does the Salt Map show EC?
No. EC is difficult to represent in situ because EC has to be measured at set moisture contents. This is because EC changes depending on the amount of moisture in the soil. Because of this, EC would move up and down somewhat inverse to soil moisture. Instead of EC, the Soil Map uses Volumetric Ionic Content (VIC) to indicate salt content.
What is Volumetric Ionic Content (VIC)
VIC is an alternate method of measuring salts in the soil. It is only available when Sentek Probes are used. Instead of measuring the Electric Conductivity (EC) of the soil, it measures the number of ions in the soil. It is not an absolute value that can be compared from site to site, but it is useful to track changes over time within the soil.
What can I use VIC for?
Leaching Salts. Some soils and water used for irrigation have excessive amounts of salt. Post-season leaching is often used to wash the salts out of the soil and leave the upper profile in a healthier condition. The effectiveness of this can be tracked using the Salt Map. Effective leaching will return the rootzone to low levels of salts.
Restrictive layers. After years of irrigation and leaching, it is common to develop a lens of salts at the bottom of the wetting zone. These are often visible in the salt map as a single row or two rows that have excessive salts. It is often difficult to get water to move below these layers, however, with proper leaching practices and perhaps the use of the proper product can help to break up these layers.
Fertilizer leaching. Most fertilizers used on fields are salts. Because of this the addition of these fertilizers can often be seen on the Salt Map. If excessive amounts of water follow the fertilizer it is possible to see the salts move deeper into the profile and away from the roots. Proper irrigation will limit leaching into deeper depths. These events are easiest to see when looking at multiple months of data at a time.
Does the amount of water affect VIC measurements.
While it is minimal, the effect of water is not completely isolated, some minor differences in VIC may occur when a soil is very wet or very dry.