The Dirt On Your Dirt Part 2 Soil PH and Salinity Issues
Soil PH can seriously affect plants health. Most areas in Utah have soils with high PH with the average being 7.5 to 8. This means that our soils are alkaline. Our soils are alkaline because of the limestone that was deposited as a result of our area’s geological history. We also have lower amounts of naturally organic matter in our soils and do not receive a lot of rain which affects soil PH. Our water supply runs through limestone laden mountains so it is also quite alkaline.
Alkaline soils can create several different problems. One of the problems we encounter with alkaline soils is when certain minerals and nutrients get bound tightly in the soil and become unavailable to plants. Iron is one of those minerals. We have plenty of iron in our soils, but it is bound tightly to soil particles because of the alkalinity of our soils. This makes it unavailable to plants. Plants that need a lot of iron to stay healthy do not do well in our area. Adding forms of iron, such as chelated iron, that are easily available to plants will help, but it is a band aid that will need to be repeated every year. Efforts to change the soil’s PH by adding sulfur, compost or other acidifying agents will be undone by the alkalinity of our water and are expensive and difficult to apply to a large enough area to make a true difference. The better option is to find plants that tolerate our higher alkalinity. Here is a link to the Conservation Garden Park’s plant finder. All plants on this list will do well in our climate and with our soil conditions.
Salinity is issue that some Utah property owners face. If you are using secondary water sourced from either Utah Lake or the Jordan River, you may have this issue. The simple way to explanation what saline soils are is to just say they have too much salt in them for most plants to be healthy. Saline soil makes it very difficult for plants to extract moisture from the soil. The best way to identify saline soils is to get a soil test done from either the USU or BYU soil labs. I will list the link to both soil labs at the end of this blog.
Saline soils can have many causes. One of the main causes in Utah is secondary irrigation water sourced from Utah Lake and the Jordan River. Utah Lake suffers from salinity both from its natural geology and from runoff containing road salt, water softeners and excess fertilizers. Other causes of high salinity are too much fertilizer, including manures, and over spray or run off from salting roads and walkways.
The only real way to remove excess salts from soil is to leach them out. The way to do that is to apply enough pure water to push the salts down into the soil profile. If you are not able to do that, the best option is to pick plants that can tolerate higher salinity. Here is a link to a page on the Conservation Garden Park’s website that discusses some plants that can tolerate saline soils.
Sodic soils are different than saline soils. Sodic soils have a high sodium, rather than high salt, content. I know they sound the same, but they are fundamentally different when it comes to soil. When the problems with sodic soils get extreme, the particles disperse and lose their structure. They also end up with a much higher PH than our normal soils. Severe problems with sodic soils are characterized by a cracked, black, greasy crust and white stains where plants won't grow.
Sodic soils do not drain because the soil structure has broken down. Sodic soils in Utah are usually found in the lower elevation, flat areas of our state where the water tables have subsided and left the sodium behind. Fixing sodic soils is a difficult process. First, you will need to replace sodium with calcium on the soil particles so the structure can recover. This can be done with lots of gypsum. Second, you will need to leach the sodium out of the soil with large amounts of pure water. Reclaiming sodic and saline soils in some areas of Utah are made more difficult by laws that do not allow runoff to flow onto adjacent properties. Leaching does not get rid of salts or sodium, it just pushes them further down into the soil profile, out of the reach of the plant’s roots. Wet years that cause water tables to rise can push salts and sodium up again so the process may need to be repeated.
If you feel you have sodic or saline soil, need to get your soil tested or help with remediation, contact the USU or BYU soil labs using the links below.
My next post will cover soil fertility.