Soil CEC and its relationship with Fertilization practices
Relationship between CEC and Fertilization Practices
CEC refers to the amount of negative charges available on the surface of soil particles. It gives an indication of the potential of the soil to hold plant nutrients, by estimating the capacity of the soil to retain cations, which are positively-charged substances. CEC is reported in milli equivalents per 100 grams of soil (meq/100g). Therefore, the CEC of the soil directly affects the amount and frequency of fertilizer application to a farm.
Recommended liming and fertilization practices will vary for soils with widely differing cation exchange capacities. For instance, soils having a high CEC and high buffer capacity change pH much more slowly under normal management than low-CEC soils. Therefore, high-CEC soils generally do not need to be limed as frequently as low-CEC soils; but when they do become acidic and require liming, higher lime rates are needed to reach optimum pH.
CEC can also influence when and how often nitrogen and potassium fertilizers can be applied. On low-CEC soils (less than 5 meg/20000g), for example, some leaching of cations can occur. Too much application of ammonium N and potassium on these soils could result in some leaching below the root zone, particularly in the case of sandy soils with low-CEC sub soils. Also, multi-year potash applications are not recommended on low-CEC soils.
Higher-CEC soils (greater than 10 meg/100g), on the other hand, experience little cation leaching, thus making fall application of N and K a realistic alternative. Applying potassium for two crops can also be done effectively on these soils. Thus, other factors such as drainage will have a greater effect on the fertility management practices used on high- CEC soils.
|SOME PRACTICAL COMPARISONS|
|SOILS WITH CEC RANGE(11-50)meq/100g||SOILS WITH CEC RANGE(1-10)meq/100g|
|High clay content||High sand content|
|More lime required to correct a given pH||Less lime required to correct a given pH|
|High water holding capacity||Low water holding capacity|
|Great capacity to hold nutrients in a given soil depth||Low capacity to hold nutrients in a given soil depth|
Taking your soil for a Soil test is very important as soil testing is the only way to determine the fertility of your soils, a particular CEC (which is indicated in soil test reports)of a soil is neither good nor bad, but knowing it is also a valuable management tool.
For more information please contact us through:
Crop Nutrition Laboratory Services Ltd.
Off Limuru Road, Limuru, Kenya
Telephone +254 (0) 711094444, + 254 (0) 720 839 933