Sodium levels in irrigation water

Hello all, I just purchased 25 acres in eastern Montana and had a water test completed. The sodium levels are at 650 ppm. If that to high to water a garden, and if so anything I can do or watch for?

Hey Jonathan. I'm concerned -- that seems rather high. It's three times the target concentration for municipal drinking water in my area.

I assume this is well water? Do you have a TDS number as well? And what is your natural soil pH? All these things fit together. It's also tougher to evaluate because irrigation related resources use electro-conductivity (micro Siemens or mho's) as the  measure rather than ppm or mg/L (which are essentially the same). But there are lots of sites giving plants/crops that are more tolerant.

I deal with high sodium/TDS well water also. Annuals don't like it, though they will tolerate some -- they will survive but not thrive. Watch for any burning on leaf edges or flowers that drop off without making fruit. Under no circumstances put this water directly on foliage. Woody perennials and established trees are tougher. I've had some luck using a deep watering wand so the salt stays below the feeder roots but the moisture percolates upward.

In our extended drought, the TDS of my well water is rising. So if the sky doesn't cooperate, I'm hardly using well water at all for the garden. I have to truck it in. Pfft!

The TDS is at 3057 and my water ph is at 8.65. I have not check my soil ph yet but I will be shortly. The well did sit basically unused for about a 1 year and a half, is there a possibility that these numbers will come down a little as I use it?

I'd be worried about applying that water to annuals with those numbers. Even applying it to perennials, if you're not getting rain washing the salt away on a regular basis, the salt will slowly build up in the soil until it's infertile.

For a small-scale, you could consider building a solar still and using that water for a small number of plants. There are a number of clever designs out of middle eastern countries, who are currently experiencing limited water availability and very high soil salinity. One of the most applicable was putting large flat pans of salty water in a closed glasshouse, and collecting the liquid condensing on the walls through a gutter system. The pans will eventually evaporate into just salt, while the clean water has been collected.

For larger-scale, there's a lot of literature on using plants to reduce soil salinity, as this has been a major issue in the worlds' arid regions for some decades now. This often involves halophytes (salt-loving plants) being planted as a cover crop to reduce soil salinity. Some examples are Suaeda salsa (and other members of this genus), New Zealand spinach (Tetragonia tetragonioides), and sea purslane (Sesuvium portulacastrum). This review article has estimated that New Zealand spinach is capable of removing 4760kg of salt per hectare per year from the soil! To put this in context, crops in Montana seem to use ~24in of water to come to maturity. With your water salinity, if you irrigated that amount, you'd be adding >500kg of salt per ha. So you might be able to do some crop rotation to keep things from getting too dire -- but remember, all that plant material full of salt has to be removed to somewhere else, or it will end up right back in the soil.

If you're keen to try something a bit more complicated, there are some folks who have managed to successfully run soil-less hydroponic systems using straight seawater (+nutrients) to grow tomatoes. This appears to work fine, whereas applying the sea water to soil directly will kill the plants.