WHAT IS IT: The need for a one-pass primary tillage tool that can work in heavy soils is certainly nothing new. But our answer is the 2625 Disk. USAGE: Soil preparation of 18-20cm BENEFITS: John deere Heavy discs are 60% heavier than competitors. A maximum 8-inch working depth, paired with disks offering weights up to 289 pounds (131.1 kg) per blade.