Soil Analysis
Analyzing a plant tells you how the crops are doing today. Analyzing the soils can help determine the trajectory of the crops for the future. Even though the majority of the elements present in soils are biochemically locked away from plants due to their oxidization state, they are potentially leachable over the long run, or possibly short run depending on how fertilizers are applied.

Analysis of soils depends on understanding your needs - whether it is essential nutrients (P, K), micronutrients (Fe, Zn), or even toxic metals (Pb, Hg).