I might as well post an answer, because there are many different things I want to address about this issue.
Firstly, as I mentioned in my comment, salt isn't exactly good for plant growth. Secondly, salt is hard to remove once it’s been saturated into the land. Using salt water to to create clouds is going to generate large areas of simply unusable land because there is no way to remove the salt without digging up all the dirt and processing it. You can't even wash it out, because that salt will flow through the rest of the land and river systems making it extremely hard for plants to grow.
Secondly, pumping water is expensive. What you’re talking about isn't 10 or 20 km. Its 100s of kilometers of piping to get the sea water there in the first place. Believe it or not, the population of Australia is pretty much entirely focused on the coast, so getting the starting pipes past the cities is going to be expensive. As you go farther out, it gets worse, because it’s harder to get equipment there, it’s more costly in terms of pumping the water and every now and again, people will have to do maintenance checks on all the equipment. If any of the salt water leaks, you've basically killed off the usable land in that area, so you need to check it pretty frequently.
Thirdly, (not sure on the exact stuff behind this, so skip this if you want) salt water is a lot more corrosive than normal water. With normal water, you just get rust due to oxidization. In salt water, you have a number of electrolysis reactions which is going to accelerate that corrosion effect even faster. Since you’re also pulling the water from the sea, you need to make sure it’s free of living creatures, small particles and so on, so that any coatings you apply don't get scratched off and the pipes don't get clogged from barnacles and what not growing on the insides. So you can't just plug a pump and pipe into the ocean and call it a day. You’re going to need to build an entire filtration plant next to the sea.
Now the solution which solves most of that would be to filter the salt water, pump the fresh water inland and use it. The biggest problem is it’s ridiculously expensive to do that compared to just pumping water out of aquifers or water tables. You can treat the water with chemicals, filters and/or boil it. In each case it consumes a ton of materials and energy to generate the water required and a ton of waste materials that will also need to be treated (filters don't last forever, you make new ones, or pump water through them backwards to unblock the holes). So you have an expensive process with an expensive distribution network when there is a cheap solution under the farmers’ feet. Desalinization is important; in Sydney we have a desalinization plant. It just hasn't been used for a while (and is costing us money), however it’s a backup plan in case things get bad, not the solution to a natural problem.
Now I finally get to the turbines. Simply put, turbines aren't going to be efficient in spraying water everywhere. They do look like giant fans, and a misty breeze on a hot day is great but they have some issues. Turbines need to be situated in areas with high winds. That isn't going to be the most of Australia. Turbines are spread pretty far apart and heavily dependent on the wind; you’re not going to cover a lot of ground using turbines... you'll get patches of growth but not the lush green fields you would imagine. The Sun is hot and so is the ground. A fine mist of water isn't going to last long enough to get deep into the ground. You might think to yourself, but I mean heavy rain, not a fine mist like those spray bottles, but simply put, there is no way to move that much water. (Think of the firefighting planes. it looks like a lot, but farming takes a constant supply over a huge area, so just because you can water your entire backyard with your hose, doesn't mean it works for a national park.)
The best thing we can do is shoot pellets into clouds to make them rain. Nature does a far better job at moving water around the world than we could ever do. Sometimes it’s too much and you get floods, and other times there is too little and you get droughts. Changing nature can cause unintended consequences (a butterfly effect) that might not show up until many years or decades later (take global warming). If it rains in one area, another area where it should have rained is missing out.