Various methods are provided for monitoring and control of soil conditions. In one example, among others, a method includes obtaining aqueous samples from suction probes (32) within a soil substrate and analyzing the aqueous samples to determine a chemical composition of the soil substrate. Amounts of an additive may be determined to adjust the chemical composition of the soil substrate. In another example, a method includes installing a suction probe within a soil substrate； drawing a vacuum to induce hydraulic conduction of aqueous solutions from the soil substrate； extracting an aqueous sample； and analyzing the aqueous sample to determine a chemical composition of the soil substrate. In another example, a method includes obtaining a composition of a fertilizer solution (FS) supplied to a soil substrate and a chemical composition within the soil substrate； determining nutrient utilization, and providing an amount of additive to produce a subsequent FS for supply.
