What's the best way to teach 8th graders about soil salinity?

November 18, 2009 2:23 PM

What is the best way to demonstrate to 8th graders the issue of soil salinity as well as showing ways to prevent or reclaim salinized soil?

I'm attempting to come up with a lesson plan for 8th graders that would educate them about soil salinity and ideally get them to come up with a creative plan to combat it at least on a small scale. I've read mostly about ways to desalinize using irrigation but if anyone knows about plants which can be used or any other methods that would be even better. The school is located in Lakeview, New Orleans so resources that deal with salinity in humid areas would be helpful. Lesson plan/ educational style resources would be best but really any information on the subject would be appreciated.

posted by bigspoon to Home & Garden (5 answers total)

How long do you have? As a medium term project you could do a variation on the bean-in-a-styrofoam-cup experiment except with several cups with different levels of soil salinity. The soil with high levels of salinity should result in beans that either don't sprout or die quickly. That's a direct demonstration of the effects high salinity can have.

If you want to go one further, for each level of salinity you can have several cups with the same level of salinity. These will be divided so that they receive different amounts of water. A possible result is that the saltier soils need more water in order for the plants to thrive.

If you want to go even further, you can not only vary the amount of water but also the salinity of the water itself. The saltier the 'irrigation' the more water needed, but of course the salty water causes the soil to become saltier over time, resulting in a vicious cycle.

In any event, once the beans have grown a bit and established roots, you can use the root ball to show how plants help soil resist erosion by holding onto soil with their roots. Soil that is too salty to support appropriate plants is more easily washed away, and without that topsoil it becomes even harder for plants to grow.
posted by jedicus at 2:53 PM on November 18, 2009

Oh I should mention that you'll want to have enough beans-in-cups to have a salinity scale ranging from normal topsoil to absurdly salty (like 10% salt or something). Having a really wide range of salinity will ensure that at least some of the plants fail to germinate or thrive.
posted by jedicus at 3:08 PM on November 18, 2009

Not completely related, but you might be interested in tamarisk, an invasive plant species in parts of the US that makes soil saltier (it draws up salt from deep water and deposits it on the surface, making other plants sad). This is pretty much exactly the opposite of "plants that can be used for desalinization" but you might find it interesting anyway.
posted by pemberkins at 5:26 PM on November 18, 2009

You could perhaps play this scene.
posted by Sys Rq at 6:31 PM on November 18, 2009

The school is located in Lakeview, New Orleans so resources that deal with salinity in humid areas would be helpful.

I don't know about humidity, but hurricane-related flooding caused higher soil salinity levels in the Lake View area. The levels weren't high enough to cause substantial problems, but it does show that salinity isn't just something that affects deserts or drought-stricken areas.
posted by jedicus at 8:27 AM on November 19, 2009