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Cation-exchange capacity (CEC) is a measure of how many cations can be retained on soil particle surfaces. [1] Negative charges on the surfaces of soil particles bind positively-charged atoms or molecules (cations), but allow these to exchange with other positively charged particles in the surrounding soil water. [ 2 ]
Laboratory tests used to diagnose a soil as dispersive focus on the cation exchange capacity of a soil sample and its cation breakdown. Soil cations are dominated by Ca 2+, Mg 2+, K +, and Na +, as well as H + in acidic soils. The exchangeable sodium percentage ( "ESP", (sodium / (total cations)) * 100 ) is a key indicator derived from these ...
Cation-exchange capacity is the amount of exchangeable cations per unit weight of dry soil and is expressed in terms of milliequivalents of positively charged ions per 100 grams of soil (or centimoles of positive charge per kilogram of soil; cmol c /kg).
The WRB defines five Reference soil Groups with a compulsory argic horizon. Only the Retisols have retic properties. The other four are differentiated according to the cation exchange capacity per kg clay at pH 7 (CEC / kg clay) in the argic horizon and according to the base saturation calculated per sum of exchangeable cations (BSeff) in the ...
Base-cation saturation ratio (BCSR) is a method of interpreting soil test results that is widely used in sustainable agriculture, supported by the National Sustainable Agriculture Information Service (ATTRA) [1] and claimed to be successfully in use on over a million acres (4,000 km 2) of farmland worldwide.
The sodium adsorption ratio (SAR) is an irrigation water quality parameter used in the management of sodium-affected soils.It is an indicator of the suitability of water for use in agricultural irrigation, as determined from the concentrations of the main alkaline and earth alkaline cations present in the water.
Humus is a negatively charged colloidal substance which increases the cation-exchange capacity of soil, hence its ability to store nutrients by chelation. [62] While these nutrient cations are available to plants, they are held in the soil and prevented from being leached by rain or irrigation. [52]
LX Lixisol (low-activity clays, exchangeable base cations ≥ exchangeable Al) AL Alisol (high-activity clays, exchangeable Al > exchangeable base cations) LV Luvisol (high-activity clays, exchangeable base cations ≥ exchangeable Al) Note: The exchangeable base cations are given in cmol c kg −1. Soils with little or no profile differentiation