Soil · 6 min

Reading a soil test: CEC, base saturation, OM

Cation exchange capacity tells you how much fertiliser the soil can hold. Below 10 meq/100g, every irrigation leaches nutrients.

Cation Exchange Capacity (CEC) measures the soil's ability to hold positively charged nutrients (Ca, Mg, K, NH4).

Sandy soils run 3 to 8 meq/100g. Loams sit at 10 to 20. Heavy clays exceed 25.

Pair CEC with base saturation: aim for 60-70% Ca, 10-15% Mg, 3-5% K. Imbalance shows up in leaves before yield.