Using Gypsum to Improve Soil and Increase Water Use, Yields and Profits

Brett Masters, soil management consultant from Rural Solutions SA and Isaac Gill, who farms in the Cleve Hills on the Eyre Peninsula of South Australia, discuss the issues with sodic soils and how using gypsum to improve soil has provided multiple benefits. High exchangeable sodium percentage in soils on Isaac’s farm has resulted in winter water logging, poor trafficability and hard setting soils.

Applying gypsum at five tonnes per hectare has provided immediate and long lasting responses, with less run off following rain events, being able to get on paddocks quicker to carry out cropping operations, increased yields and cleaner water flowing into farm dams.

This is another video supported by the Social Media in Agriculture project funded by Australian Government’s Caring for our Country initiative.

Basically looking at the gypsum response on some sodic soils. This soil pits fairly typical of the soil types around these hills areas. What we’re finding as we go down the profile is the top soil – the 0 to 10 centimeter layer – is it is fairly nice friable, a well structured loamy soil, is a hard pane, possibly through cultivation, years of cultivation on that soil top at about 15, 20 centimeters.

Issues with Clay Layers and Poor Soil Structure

And underneath that hard pan we’re finding a clay layer which is sodic or it’s dispersive, it has fairly poor structure. The structure breaks down when it gets wet which limits root growth deeper into the profile. So the difficulty that we have with this dispersive clay, it can be very hard to work the paddock. When the soil gets wet the structure breaks down and it becomes very slippery and when it dries out it forms a sealing layer like concrete.

The reason we see the breakdown of soil structure at that clay layer is basically because of the amount of sodium that is present, sodium and potassium that’s present in the soil. The exchangeable  sodium percentage is very high. It’s around 17, 18 percent. The approach that Isaac’s taken there is actually to apply gypsum to the site.

Gypsum Replaces Sodium with Calcium

What gypsum does is it replaces the sodium in the soil with calcium, and calcium forms a much stronger bond between the clay particles. allows better infiltration and better root growth down the profile. Gypsum is fairly soluble. So it will move down the profile with a decent rain, and you will see responses in the first year or couple of years.

What we’re doing is replacing the sodium with the calcium and the gypsum, that we’re expecting that to be a long term benefit. We knew we were having troubles when we couldn’t get on our land very well in the winter time. Got on to Brett and two trials from two ton, four ton, five ton, and eight ton, and then two ton of lime and five ton of gypsum, and try to see which one would be the best and for the longest lasting.

We’ve been putting gypsum for three years, and we first started at five ton, and five ton seems to be just a good number. And then Brett’s done all the trials and five ton, or just under five ton, that uses what we require. And we can see immediate response. In the first year we can get on our paddocks quicker.

Improved Water Penetration and Retention with Gypsum Application

After a rain event the moisture is penetrating the soil profile quicker and longer-lasting, we’re not having as much runoff off our property. so the water is staying on our farm and in their soils and helping their crops grow. We can see immediate benefit by being able to get out on their paddocks in the winter time and spray and spreading urea. One of the trials that we have done there is a yield benefit with a five ton of gypsum and two ton of lime, we get our gypsum from Lake Gilles gypsum pit. That’s about 85 kilometers from where we live and that’s sort of fair expense in carting  it at costs around the 12 dollars a ton for the gypsum and similar for freight.

And by the time you put five ton to the hectare. With spreading costs you’re looking at about 125 to 150 dollars a hectare. Since applying the gypsum Where I were to drive across the paddock, and not need four wheel drive as much and where I were to get across the paddock so they aren’t putting big trenches.

Gypsum Reduces the Amount of Run Off

One thing that we have noticed over a period of time is that the water is a lot less runoff in the paddocks. And the water that has run off in the paddock isn’t a milky cloudy colour that it was before we started applying gypsum. The dams have changed from being a milky color to a clear water that you can in the dams and see to the bottom.

One way the landholder can actually go out into their paddock and test to see whether their soil may be responsive to gypsum is to actually take a clod of soil and put that into distilled water or rain water. If we don’t have distilled water and to wait for half an hour and to see what the effect of dropping that clod into the rain water will be.

If the water around the soil particle turns milky then we’re expecting that we’d get some response from gypsum. Applying gypsum can be an effective tool for addressing those soil structure issues. and actually making the paddock more workable and getting growth production benefits from that.