I agree with Andy about 95%, I like the mats produced by Model Scenic better then Silflor, but I think this is just a preference, I have used both and don't see a big difference in the end results. His dirt and PVA glue idea is great and a very inexpensive and effective way to make earth.
Also even though Silflor is one of the best grass products out there it is only 1 of 3 different brands that I consider using, the other two are the above mentioned mats by Model Scenic, a Czech made product available from Military Miniature Warehouse, and the other by Heki, available from Scenic Express where you get the Silflor grass. These are not cheap but by far the best you could buy.
There are much less expensive ways to make turf, the easiest is just use any of the turf products by Woodland Scenics. They are just a powder that when applied to the groundwork of the diorama base looks like grass (not like Silflor grass but still grass), or use a static grass product. The only drawback to a static grass is you have to make or buy an applicator. The static grass is similar to the turf but stands up like grass when an electric charge is given to the individual pieces of material. I have made my own applicator and it was easy, cost about $8 and took only about 20 minutes to actually make. It took more time to watch the YouTube video on "how to make a static grass applicator" then to actually make the applicator.
Good luck and I hope that helps.