Greenway Biotech Tomato Fertilizer 4-18-38 is a water-soluble fertilizer for tomatoes. It guarantees 4% nitrogen, 18% available phosphate (P₂O₅), and 38% soluble potash (K₂O), with EDTA-chelated iron, manganese, zinc, and copper plus boron and molybdenum.
In a garden bed or field, size it by a soil test: pounds of product equal the pounds of potash your test recommends, divided by 0.38. In hydroponics, University of Florida IFAS builds a greenhouse tomato solution on a 4-18-38 premix at 0.64 g per liter, with calcium nitrate in a separate stock tank.
It contains no calcium or magnesium and little nitrogen, so plan those from other fertilizers, and keep its concentrate apart from calcium concentrates. Use it only on the crops on its label, because it contains boron.
Registered with the California Department of Food and Agriculture (CDFA). A 2016 independent heavy-metal test of one sample found arsenic, cadmium, and lead below the laboratory’s detection limits. Packed in Madera, California, in 1 to 25 lb sizes.
