Wenjing Guan

Vegetable Crops Hotline Editor & Clinical Engagement Assistant Professor
Department of Horticulture and Landscape Architecture
Area(s) of Interest: Commercial Vegetable and Melon Production
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​You might remember seeing cation exchange capacity in soil test reports. Recently, I have been asked about what it means. This is one of the important soil characteristics that we need to understand.  Firstly, we need to know what cations are. Cations are positively charged ions. There are several. The ones very important for plant growth are calcium (Ca2+), magnesium (Mg2+) and potassium (K+). Soil particles are negatively charged. They can hold positive charged cations. When plants absorb nutrients from the soil solution, these bound nutrient cations are exchangeable with other cations in the soil solution and become plant available. Therefore, CEC describes the soil’s capacity to supply nutrient cations to the soil solution for plant uptake. Sands do not have the quantity of negative charges that clays and organic matter do. Thus sandy soils generally have the lowest CEC. Soils with lower CEC have less ability to retain cation[Read More…]