We have used Cleris AD 4000 fertilizer spreader that has a hopper volume of 3,55 m3 (loading capacity about 4.300kg). Sometimes we have used Cleris AD 6000 fertilizer spreader which is more modern but with a similar performance. The big difference is it has a hopper volume of 5,25 m3 (loading capacity of 6.300kg). Other key features are: reinforced gearbox, easy and simple adjustment, stainless steel spreading discs, robust and reliable construction, independent hydraulic opening and closing, working width from 10m to 18m. These fertilizer spreaders are well know in my area, they work very fine and allow us to work a long time without uploading them again. Our Agrotron 85 can work very easily with them and we can get a working speed of 12 km/h without problems and with a PTO configuration of 540 r.p.m.
You can watch two videos from here: Video 1 Video 2