Jack's Nutrients Magnesium Sulfate Epsom Salts vs MasterBlend 4-18-38 Complete Combo Kit

Buy the Jack's 25 lb bag if you already run a complete nutrient program and just need magnesium and sulfur in bulk. Buy the MasterBlend kit if you want a full three-part feed for tomatoes and vegetables in one box. Jack's is a single-ingredient supplement, so it cannot feed a plant on its own; MasterBlend is a complete recipe but comes in a much smaller 2.5 lb kit. Owners of MasterBlend rate it well, and its 4-18-38 plus calcium nitrate is a long-standing tomato formula.

• Choose the Jack's Magnesium Sulfate if you mix your own nutrients and want a large, pure supply of magnesium and sulfur for the Jack's 3-2-1 program or any low-magnesium soil.
• Choose the MasterBlend kit if you want a complete three-part feed for tomatoes and vegetables without sourcing calcium nitrate and Epsom salt separately.