4-2 Fertilize with NPK + Iron. Azomite trace minerals are a must. Published May 4, 2011 at 800 × 600 in Gardening Made Easy – For Moderate to Arid Climates ← Previous / Next → Fertilize with Nitrogen, Phosphorous, Potassium, and Iron in Utah Utah soils need nitrogen, phosphorous, potassium and iron, so make sure your fertilizer contains those essential nutrients.