Effects of clay mineralogy and physico-chemical properties on potassium availability under soil aquic conditions

Abstract

Aquic conditions performed for paddy cultivation may cause many nutritional problems. Clay mineralogical composition plays an important role in this relation by affecting many physico-chemical and biological characteristics of soils. Three forms of K including unavailable, slowly available and readily available K, exist in equilibrium in the soil system. Relationships between soil potassium forms with the clay mineralogical suite and physico-chemical properties were determined in 33 soil samples collected from five from paddy soils, two from kiwi fruit and one from citrus land pedons in the North of Iran. Mineralogical analyses showed that smectite, illite and vermiculite were the most abundant clay minerals in the studied soils. Mean soluble and exchangeable potassium in paddy soils were rather low compared to non-paddy soils due to potassium fertilization in non-paddy soils. Non-exchangeable potassium in the samples containing smectite as dominant clay mineral was lower than the samples dominated by vermiculite, hydroxy-interlayer vermiculite (HIV) and illite. Inability of the studied soils for potassium fixation was related to prevailed montmorillonitic type of smectite, which its layer charge originates from octahedral sheet. Significant correlations (0.56 ** , 0.54 ** , 0.56 ** ) were obtained between exchangeable potassium and clay content, organic carbon and cation exchange capacity respectively. Therefore, taking into account both exchangeable and non-exchangeable K beside clay mineralogy and physico-chemical properties gives better indications for K potential and soil-quality management, compared to exchangeable form of K alone.

Influence of Clay Minerals on Some Soil Fertility Attributes: A Review

“…A combination of soil mineralogy, physicochemical properties and soil moisture regime gives a better insight into the effects of clay minerals on different forms of K in soil [64] [65] [66]. Raheb and Heidari [65] observed that non-exchangeable potassium in smectite-dominant soils was lower than those dominated by vermiculite, hydroxy-interlayered vermiculite and illite, and there were significant correlations between exchangeable potassium and clay content, organic carbon and cation exchange capacity. Similarly, Bajwa [64] observed that beidelitic clays can fix > 80% of K under aquic soil conditions.…”

Potassium forms in calcareous soils as affected by clay minerals and soil development in Kohgiluyeh and Boyer-Ahmad Province, Southwest Iran

“…Similar to exchangeable K, the non-exchangeable K in the study area was also higher in surface soils than in subsurface soils and was significantly correlated with illite (Pearson correlation coefficient of 0.361), vermiculite (0.373), smectite (0.324), clay content (0.290), CEC (0.441), OC (0.277) and CCE (-0.447) (Table 4). Raheb and Heidari (2012) found that due to the thermal and moisture conditions for weathering of primary minerals, the exchangeable and non-exchangeable K contents in surface soils were higher than those in subsurface soils. In the study area, some representative pedons such as 51 (Alfisols), 33 (Alfisols), 36 (Molisols), 49 (Alfisols) and 39 (Vertisols) had the larger amount of non-exchangeable K in surface soils (956,699,690,680 and 541 mg/kg, respectively) and subsurface soils (892,421,389,463 and 541 mg/kg, respectively), while subsurface soils in the Entisols including pedons 53, 29, 34 and 47 had the lower amounts of non-exchangeable K. Alfisols in semi-arid regions are the most well-developed soils with moderate leaching.…”

“…It seems that organic matter plays a more important role than smectite mineral in retaining exchangeable K in the studied soils. Raheb and Heidari (2012) stated that the smectitic soils are rich in exchangeable K, whereas the predominant illite soils exhibit low amount of exchangeable K. In addition, there are significant correlations of exchangeable K with CEC and OC.…”

“…Exchangeable K is electrostatically retained on the outer surface of clay and humic substances, and is available for plants (Barré et al, 2008). Non-exchangeable K plays an important role in supplying available K, particularly in soils containing K-bearing minerals (Raheb and Heidari, 2012). This form of K is fixed in interlayer of 2:1 clay minerals and could be released gradually (Rees et al, 2013).…”

Quantity-intensity characteristics of Potassium (K) in relation to potassium availability under different cropping system in alluvial soils

“…E-mail: mslalit@yahoo.co.in Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License in the soil (Havlin et al, 1999). Hence the K availability in the soil solution (intensity) and the inherent capacity of the soil to buffer this concentration against changes are among the important parameters that determine effective availability of K to plants (Grimme, 1976;Raheb and Heidari, 2012). In some cases even though the soil contain considerable amount of total K, the availability to plants are negligible.…”