Cationic equilibria in selected soils and soil materials

[摘要] The relationship between exchangeable potassium andARKe was studied for four agronomically-important soils of theO.F.S. Region and two commercial clays. Some attention wasalso given to the Q/I and Gapon relationships for these soilsand claysc The effects of some factors, e.g. sodium leveland clay:solution ratio, on these parameters were also investigatedoLinear relationships between Kex and ARKe were found forall soils and clays used. In most cases the graphs relatingKex to ARKe had intercepts different from zeroo At extremelyhigh levels of K saturation in bentonite the slopes of thegraphs changed and different linear relationships were obtained,the slopes of the upper portions being lower thanthose of the lower portions.At high Kex levels a fairly good numerical similaritybetween -∆K and Kex was found in most caseso At Kex level near EK , i.e. that level of Kex where ARKe becomes zero,-∆KO decreased relative to Kex. At these low Kex levels-∆KO was therefore not a good indication of Kex.PBCK proved to be a very constant property of a soil orclay, being unaffected by most experimental conditions andby level of K saturation. The PBCK values of these soilswere very lowo PBCK of bentonite was strongly influencedby clay: solution ratio when ∆K values were expressed as meper 100g clay.Increased sodium levels changed the relationships betweenKex and ARKe, but did not cause poorer relationshipsbetween these two parameters. The magnitude of the effectof sodium was a function of the amount of sodium brought intothe system and the latter was largely a function of theCEC of a soil.

[发布机构] University of the Free State