Fertigation

Compared to broadcast or banded application, fertigation moves the question from "how much fertilizer per hectare per season?" to "how much per plant per week, in this exact growth stage, given today's water EC and last week's leaf analysis?". The economic return shows up as fewer kg of fertilizer applied for the same yield (typically 20–40% less N) and tighter nutrient timing aligned with crop demand curves.

The practical workflow has three loops. (1) **Program design**: per-stage weekly targets — for date palms a typical Year-3 vegetative entry is 120 g N + 50 g P2O5 + 80 g K2O per palm per week; for tomato fruit-set 80–120 kg N/ha/week split across 3 events. (2) **Compatibility checking**: calcium nitrate cannot share a tank with phosphate or sulfate sources because Ca-P or Ca-S precipitates clog the lines and starve the field; potassium chloride should not be used with saline water (chloride amplifies). WiseYield's engine flags these inline and either splits events or proposes substitutes (K2SO4 for KCl, separate Ca tank). (3) **Solution-EC math**: dissolved fertilizer adds EC on top of the irrigation water — Σ(kg × ec_at_1g_per_l) / waterLiters. Final solution EC should sit below the crop's tolerance threshold to avoid root damage; greenhouse tomato programs run 2.0–3.0 dS/m, date palms tolerate 4.0+.

WiseYield's fertigation engine (`@wiseyield/data-pipelines/fertigation`) handles these three loops as one transparent pure function. The output is a per-plant-unit weekly event with planned fertilizer mix, water volume (including leaching uplift from §9.2), and a formula string that explains every multiplier — soil-status correction, leaf-status correction, salinity correction, basis multiplication. Compatibility warnings surface in the same calendar cell.