Soil fertility is defined by the plant growth, typically the greater soil fertility the more plant growth. The issue is that different plants need different types of soils and have different nutrient or water requirements. Soil fertility involves having typically adequate soil carbon levels, having good tilth, not compacted, good water infiltration and water holding capacity, and both water and nutrients can be retained. It’s a value that is defined by what the plant requires to grow. And good soil fertility is critical for any crop productivity, only with fertile soils will we achieve the yield potential of a given soil.