Challenger Category: Micronutrients, Nutrient Paks/Specialty A starter fertilizer for seed or transplants. Product Description Challenger may be used as a starter fertilizer with seed or transplants, soil applied and/or foliar feed. Product Label Product Flyer Guaranteed Analysis: Total Nitrogen (N) Available Phosporic Acid Soluble Potash (K20 Copper (CU) Zinc (zn)