Exchangeable Potassium Percentage Research Articles

Potential nutritional value of olive-mill wastewater applied to irrigated olive (Olea europaea L.) orchard in a semi-arid environment over 5 years

Abstract Controlled spreading of olive mill wastewater (OMW) on cultivated soils is a low-cost disposal method of an otherwise problematic pollutant, with potential recycling of plant nutrients. The nutritional value of successive OMW applications was examined in an intensive olive orchard grown on sandy loam soil in a semi-arid region. Application at 50–150 m3 ha−1 y−1 for 5 years had no negative effects on tree vegetative growth, fruit yield or oil quality. OMW application did not increase N content in the soil or plants; yet, it caused a consistent increase in soil P and K contents and significantly affected diagnostic leaf P and K concentrations. It also led to a significant increase in exchangeable potassium percentage (EPP) already from the first application, and soluble K migration to deep soil layers after 3 years of successive applications. Soil tillage after OMW application did not affect N, P or K dynamics in the soil or uptake of these nutrients by plants. Controlled application of OMW to intensive olive orchards can be a significant source of K and P and thus save on fertilizers without negatively affecting tree performance.

Impact of monovalent cations on soil structure. Part I. Results of an Iranian soil

AbstractThis study investigated the impact of monovalent cations on clay dispersion, aggregate stability, soil pore size distribution, and saturated hydraulic conductivity on agricultural soil in Iran. The soil was incubated with treatment solutions containing different concentrations (0-54.4 mmol l−1) of potassium and sodium cations. The treatment solutions included two levels of electrical conductivity (EC=3 or 6 dS m−1) and six K:Na ratios per electrical conductivity level. At both electrical conductivity levels, spontaneously dispersible clay increased with increasing K concentration, and with increasing K:Na ratio. A negative linear relationship between percentage of water-stable aggregates and spontaneously dispersible clay was observed. Clay dispersion generally reduced the mean pore size, presumably due to clogging of pores, resulting in increased water retention. At both electrical conductivity levels, hydraulic conductivity increased with increasing exchangeable potassium percentage at low exchangeable potassium percentage values, but decreased with further increases in exchangeable potassium percentage at higher exchangeable potassium percentage. This is in agreement with earlier studies, but seems in conflict with our data showing increasing spontaneously dispersible clay with increasing exchangeable potassium percentage. Our findings show that clay dispersion increased with increasing K concentration and increasing K:Na ratio, demonstrating that K can have negative impacts on soil structure.

Annual spreading of olive mill wastewater over consecutive years: Effects on cultivated soils' physical properties

AbstractSeveral studies cautioned against potential negative effects of controlled olive mill wastewater (OMW) application on soil physical properties that could be associated with the possible adverse effects of K on soil structure stability. The objective of the study was to examine the effects of annual application of OMW over several years on selected physical properties of the upper soil layer (0–10 cm) and their link to exchangeable K levels. Two experimental field platforms were studied: field crops grown in a tilled clay soil (3 years of OMW application) and an olive orchard grown in a sandy‐loam soil (5 years of OMW application). In the clay soil, OMW application did not affect organic carbon (OC) and only slightly increased exchangeable potassium percentage (EPP) from 3.3 in the control to ~4.5 in the OMW‐treated plots. In the sandy‐loam soil, application of different rates of OMW resulted in an increase in both OC and EPP (>20) compared with the control (8). For both soils, addition of OMW improved aggregate stability; yet for the clay soil, the increase was not associated with changes in EPP or OC. In the sandy‐loam soil, aggregate stability was positively correlated with OC and EPP. Soil hydraulic conductivity, tested for the sandy‐loam soil only, was not affected by OMW application. Overall, our study shows that consecutive 3 to 5 years of controlled OMW application in the range of 50–150 m3 OMW ha−1 y−1 does not result in the deterioration of soil physical and hydraulic properties.

Modifications in selected soil attributes as influenced by long-term continuous cropping in a calcareous semiarid environment

Intensified agriculture and irrigation practices over a long-term are an important factor in soil change phenomena that can appear some unwanted effects on soil attributes. To examine this hypothesis, physicochemical properties and clay mineralogy of four major soil types (Typic Haploxerepts, Typic Xerorthents, Typic Calcixerepts, and Fluventic Haploxerepts) under sunflower cultivation over five decades and adjoining virgin lands were investigated in order to monitor changes caused by long-term cropping. The comparison of cultivated soils and virgin lands indicated that cultivation resulted in an increase in clay (3–28 %) and silt (3–25 %) content, along with a decrease in sand content (2–17 %), resulting of the cultivation practices. For most of the examined soils, soil pH and calcium carbonate equivalent were marginally increased as 0.1–0.23 unit and 4–26 mg kg−1, respectively, following intensive cropping. A relative depletion was manifested in mean value of soil organic carbon (4–18 %), soluble K (47–197 %), exchangeable K (21–34 %), available K (20–34 %), potassium absorption ratio (43–45 %), and exchangeable potassium percentage (26–54 %) due to continuous sunflower cropping. Comparing with the virgin lands, the cultivated soils showed a considerable rise in electrical conductivity (18–122 %), sodium absorption ratio (18–122 %), exchangeable Na (4–48 %), and exchangeable sodium percentage (10–47 %) likely due to the chemistry of the irrigation water used, as well as the chemical interaction between the irrigation water and its receiving soils. Over the five decades of cultivation, some changes in the X-ray diffraction pattern of illite and smectite were observed mainly as result of cropping and K depletion as well as alternating wet–dry periods induced by irrigation practices.

Effect of K+ on Na - Ca exchange and the SAR-ESP relationship

In Australia, application of winery wastewater to land is increasingly being viewed as the most environmentally sound and cost-effective means of disposal. This wastewater contains high concentrations of both sodium (Na+) and potassium (K+), which have the potential to accumulate in the profile of irrigated soils and adversely alter physical properties such as aggregate stability and hydraulic conductivity. Cation exchange equilibria in soil of mixed illite and kaolinite mineralogy have been investigated in binary Ca–Na and Ca–K systems and in a ternary Ca–Na–K system. In the respective binary systems, resulting exchangeable potassium percentage was nearly twice the corresponding exchangeable sodium percentage (ESP), indicating a high binding affinity of K+ in this soil. In a ternary system, soils were equilibrated with solutions of differing sodium adsorption ratio (SAR) and potassium adsorption ratio (PAR) within ranges typical of winery wastewater. The presence of K+ had a significant effect on the relationship between SAR and ESP, whereby ESP decreased with increasing PAR. Resulting ESP in the ternary system was consistently lower than in the binary system. Cation selectivity between solid and solution phases in the ternary system was calculated from the Vanselow and K-selectivity coefficients and showed a decreasing selectivity for Na+ with increasing K+ in solution. It is expected that, due to the high K+ content of winery wastewater (i.e. >400 mg/L), adsorption of Na+, and subsequent ESP, will be less than in wastewaters of comparable Na+ concentration yet absent K+.

Clay mineral associations in soils formed under Mediterranean-type climate in South Africa

The objective of the study was to determine clay mineral associations in soils of the winter rainfall area of South Africa and to relate them to dominant soil-forming factors. Clay mineral compositions from 69 profiles, involving 190 samples, were determined by means of X-ray diffractometry. Mica proportions decreased predominantly (R2 = -0.59) through weathering. The exchangeable potassium percentage (EKP), however, also played a significant role and mica was absent from soils with EKP = 0. Smectite, vermiculite and hydroxy-interlayered vermiculite (HIV) occurred in 60, 28 and 62 samples respectively, and illite/smectite (I/S) in 44. The number of samples containing swelling clays decreased with increasing rainfall while the percentage of HIV increased. The most important agricultural aspect is that many, if not all, vermiculites, smectites and l/S phases, are highly K-fixing. As a result of the geothermal history of the area, chlorite and mica must have been by far the dominant minerals in the parent rock. Chlorite was absent from all soil samples and is therefore the most unstable precursor mineral. The kaolinite content was virtually unrelated to weathering (R2= 0.1) but probably reflects the original amount of chlorite.

Influence of exchangeable potassium on soil erodibility

Abstract. Regular application of slurry manure in large quantities is thought to degrade soil structure and increase erodibility. One hypothesis links this to the large input of potassium which increases the exchangeable potassium percentage (EPP) and, thereby, dispersion. The effect of EPP on erodibility was quantified in three experiments. In the laboratory, eleven rainfall experiments were conducted using a silty topsoil from a typic Hapludalf which was fertilized to EPPs of 4 to 18%. Field rainfall experiments on 22 Inceptisols and Alfisols were used to examine whether the long‐term application of monovalent cations (Na+, K+ and NH4+) with slurry manure had changed soil properties, especially erodibility. In addition, erodibilities of 32 soils determined with natural and simulated rains were taken from literature. The experiments on these 65 soils together covered a wide range of soils, slopes and rainfalls. Dispersion by a large percentage of highly hydrated ions (K+, Na+) reduced the infiltration rate faster, caused runoff up to 5 min earlier, and increased sediment concentrations by 15g/l compared to low EPP soils. These changes increased soil erodibility of the Universal Soil Loss Equation (USLE) by 0.021 t × h/N × ha (where N = Newtons) for each 1% increase in EPP + ESP (exchangeable sodium percentage). The ESP contributed little to this increase as ESP was less than 1/10 of EPP in the experiments.Fields with long‐term manure application had similar chemical, physical and microbiological soil properties as fields without slurry manure except for slightly greater pH (+ 0.6) and P (+ 17 mg/kg) values. We conclude that, as long as the potassium input and output are balanced, the long‐term use of slurry manure does not increase erodibility.

Effects of high pH solutions with large monovalent cation concentrations on cation exchange properties

Disposal of strongly alkaline industrial liquid wastes, which contain large monovalent cation concentrations, by means of land treatment systems is becoming increasingly common. This study investigated the effects of solutions with large monovalent cation concentrations and high pH on cation exchange properties in four New Zealand soils with different clay mineralogies. The soils were shaken with a range of concentrations (0–0.3 M) of NaOH, KOH, NaCl, and KCl. Cation exchange capacity (CEC) and exchangeable cations (Ca2+, Mg2+, K+, and Na+) were measured following shaking and washing procedures. Although the hydroxide solutions dissolved significant amounts of organic matter from all soils, there was still a net increase in CEC measured at all hydroxide concentrations. The magnitude of the CEC increase was dependent on hydroxide concentration. The increase in CEC is attributed to newly generated negative charge on surfaces which possess variable charge (i.e. pH dependent) characteristics such as edge sites of clay minerals, sesquioxides, and the undissolved organic matter remaining in the soil. In contrast to hydroxide solutions, no increase in CEC was measured in chloride-treated samples. Increases in the concentration of all treatment solutions resulted in increases in the exchangeable ion concentration of the index cation used in the treatment solution (either Na+ or K+) and decreases in concentration of the other three exchangeable cations. In general, higher exchangeable sodium percentage (ESP) values were measured in samples treated with NaOH than samples treated with NaCl at all concentrations. Similarly, higher exchangeable potassium percentage (EPP) was measured in samples treated with KOH than samples treated with KCl at all concentrations. The higher ESP and EPP values recorded when hydroxide solutions were used as treatments are attributed to the newly generated negative charges being counter-balanced by the monovalent index cation present in the treatment solution. It is suggested that existing equations commonly used to predict ESP and EPP values are unsuccessful for accurately predicting changes when soils are treated with hydroxide solutions, due to their inability to account for the newly generated exchange sites. The equations did, however, adequately predict the effects of both chloride solutions on ESP and EPP.

Exchange equilibria of potassium in some red, black and alluvial soils of India .II. Effect of temperature on K+-Ca2+ exchange

Potassium-calcium exchange equilibria in red (kaolinitic), black (smectitic) and alluvial (illitic) soils of India were studied at 25�C, 40�C and 65�C. The different selectivity coefficients increased in all the soils when the temperature was raised from 25�C to 40�C. Out of seven soils, only in three cases did the exchangeable potassium percentage (EPP) increase with rise in temperature from 25�C to 40�C. When the temperature was further raised to 65�C, EPP as well as selectivity coefficients in the different soils decreased to values less than those observed at 25�C. Similar inferences regarding K selectivity were drawn from normalized exchange isotherms. The sequence of variation in selectivity coefficients with increasing K saturation was Kv > KKDO > KN >KG, where the coefficients are those of Vanselow (Kv), Krishnamoorthy, Davis and Overstreet (KKDO), Gaines and Thomas (KN), and Gapon (KG). The sequence of the coefficients was unaffected by increasing the temperature from 25�C to 65�C. Potassium-calcium exchange was more spontaneous at 40�C than at 25�C. It was non-spontaneous at 65�C in all but the smectitic soils.

Exchange equilibria of potassium in soils, V. Effect of natural organic matter on K-Ca exchange

Exchange equilibria of K-Ca were studied in five soil samples (Anglberg surface, ABS; Anglberg subsurface, ABSS; Ottenhofen surface, OHS; Ottenhofen surface limid, OHSL; Buchhofen surface, BHS) from the Federal Republic of Germany. These samples had a wide difference in their clay content, clay mineralogy, CEC, K-fixation capacity, organic matter (OM), specific surface area, and surface charge density (SCD). Untreated and H 2O 2-treated samples were Ca-saturated and equilibrated with KCl+CaCl 2 solutions at a constant chloride concentration of 0.025 M 1 −1 in the equilibrium solutions. The experimental results were described, using the Gaines and Thomas, and Babcock and Duckart thermodynamic approaches, and various selectivity quotients. Out of five, two soil samples showed a decrease in the Gapon ( K G ) and Vanselow ( K V ) selectivity quotients in the lower K-saturation (i.e., 0–15 exchangeable potassium percentage, EPP, in ABS; 0–30 EPP in ABBS) zone on oxidation of OM. In the remaining three soil samples, K G and K V increased with H 2O 2-treatment for the whole exchange isotherms. The Gaines and Thomas standard free energy for K-Ca exchange ( ΔGo) decreased in all but one (i.e., ABSS) and Babcock and Duckart ( ΔGo′) in all the soil samples on OM oxidation. The values of ΔGo were less negative than those of ΔGo′ for comparable soil samples. The positive or negative effect of OM on K-preference has been ascribed to the “resultant” of the two opposing phenomena, viz., an increase in SCD and “low K-specific adsorption sites” (causing a decrease in K-preference), and an increase in the internal: external surfaces due to organo-mineral colloids (causing an increase in K-preference).

Effect of Exchangeable Potassium on the Hydraulic Conductivity of Smectite-Sand Mixtures

AbstractChanges in hydraulic conductivity of smectite-sand mixtures (using four reference smectites) as a function of the concentration (0.01, 0.003, 0.002, 0.001 M Cl- and distilled water) and potassium adsorption ratio (of 2, 4, and 6) of the percolating solution were measured. Swelling and dispersion of the clays were evaluated from the changes in hydraulic conductivity of the mixture and from the clay concentration in the effluent.The effect of exchangeable potassium percentage (EPP) on the hydraulic conductivity of the smectites depended on the charge density of the clays. The effect of potassium at EPPs <20 on the hydraulic conductivity of smectites having high charge density was negligible. Conversely, the hydraulic conductivity of smectites having low charge density (smectites from Wyoming and Belle Fourche, South Dakota), changed markedly when leached with dilute solutions as the EPP of the clay increased. The dispersive effect of exchangeable potassium on low-charge smectites was similar to that of exchangeable sodium. The low hydration energy of the K+ cations, coupled with the strong electrostatic attraction forces between platelets of smectites with high charge density account for the “inefficiency” of K+ in dispersing these smectites.

Effects of zero tillage and stubble retention on some properties of a cracking clay

Soil chemical and physical properties of a black cracking clay were measured after five years under a zero tillage and stubble retention trial. Stubble retention slightly increased the organic carbon content of the 0-10 cm layer, and the dispersion ratio of the 0-4 cm layer. Stubble retention increased dry aggregate size in the 0-4 cm layer of the zero tilled treatments, apparently due to a reduction in the rate of drying of the surface after rain. Changes in the distribution of cations in the surface soil developed in the absence of tillage, with lower exchangeable sodium percentage (ESP) and higher exchangeable potassium percentage in the 0-4 cm layer under zero tillage. The reduction in ESP in the 0-4 cm layer under zero tillage also reduced dispersion ratios. The ratio CEC : % clay for the 0-4 cm layer was reduced by zero tillage. Chloride profiles gave evidence for increased deep infiltration under zero tillage. This is attributed to the presence of cracks that were not closed by tillage.

EXCHANGE EQUILIBRIA OF POTASSIUM VERSUS CALCIUM AND SODIUM IN SOILS FROM A SEMIARID REGION, INDIA

We studied the potassium-calcium and potassium-sodium exchange equilibria on three soil samples differing in their organic carbon content (OC) and cation exchange capacity (CEC). Homoionic (Ca or Na saturated) soils were equilibrated, with the solutions having a large range of potassium adsorption ratios (PARs) at 50 meq L-1 total electrolyte concentration. We analyzed the data on exchange equilibria, using a thermodynamic approach and various selectivity coefficients. The normalized exchange isotherms for K+-Ca2+ systems suggested higher specificity for K+ to Ca2+ in the first 50 to 75 percent of K+ saturation. In the K+-Na+ system the specificity for K+ to Na+ was, however, higher for the whole range of exchange isotherms. The soil high in OC (Soil 1) had higher preference for K+ than the soils low in OC (Soils 2 and 3). The values of standard free energy change of the exchange reactions (ΔGr°) for K+-Ca2+ and K+-Na+ systems were negative for all the three soils tested. These values were, however, more negative for K+-Na+ than for K+-Ca2+ systems, suggesting higher preference for K+ in the former. A comparison of ΔGr° values suggested that the effect of CEC on the K+ specificity of these soil samples was only marginal, though that of OC was quite spectacular. The values of the Gapon selectivity coefficient (KG) decreased first sharply and then gradually with the increase in exchangeable potassium percentage (EPP). On the basis of (KG), the exchange isotherms were divided into three zones, representing exchange sites with high, medium, and low specificities for K+. The arbitrary limits for the three zones were < 5, 5 to 38, and >38; > 4, 4 to 15, and >15; and > 5, 5 to 15, and > 15 for Soils 1, 2, and 3, respectively. The exchange selectivity coefficient (KN) and AGr° for K+-Na+ systems were different only marginally for Soils 1 and 2. However, for K+-Ca2+ systems, the values of different selectivity coefficients (viz., KG, Vanselow selectivity coefficient, and Krishnamoorthy-Davis-Overstreet selectivity coefficient) and AGr° for Soils 1 were considerably different from those for Soil 2. This suggested a differential role of OC on changing the selectivity of soil for K+ in K+-Ca2+ and K+-Na+ systems.

Exchange equilibria of potassium versus calcium-plus-magnesium in soils of arid and semi-arid regions, India

Exchange equilibria of potassium vs. calcium + magnesium were studied on samples of eight soils derived from alluvium but differing in CEC, texture and other properties. The K + exchange isotherms were drawn using solutions of different potassium adsorption ratios (PARs), i.e., 0.1, 0.2, 0.4, 0.6, 0.8, 1, 2, 5, 10, 20, 50 and 100 mmol 1 2 l − 1 2 at a total electrolyte concentration of 50 me.l −1. The specificity of the exchange sites for K + decreased first abruptly and then gradually with increasing PAR of the equilibrium solution. The Gapon coefficient ( K G) vs. exchangeable potassium percentage (EPP) curves were arbitrarily divided into three broad classes of specificities. The maximum, medium and minimum specificities for K + adsorption were attributed to the edge-interlayer sites of mica, the sites in wedge-shaped interlayers of partially weathered mica and integrade mica-montmorillonite packets, and the planar sites, respectively. The first two zones of specificities were explained on the basis of geometric configuration of exchange sites and the last on the basis of electrostatic forces, using the theory of a diffuse double layer. The normalized exchange isotherms showed that at low EPP the equivalent ion fraction of K + on the exchange complex was greater than that in the equilibrium solution, whereas the reverse was true at high EPP, the inflexion point being dependent on soil type. The selectivity coefficients for K +(Ca 2+ + Mg 2+) were calculated using the Vanselow ( K V), Krishnamoorthy-Davis-Overstreet ( K KDO) and Scheffer-Ulrich ( K SU) equations. None of these coefficients was found to be constant with K + saturation showing thereby the inability of these equations to predict K +(Ca 2+ + Mg 2+) exchange in these soils.

The effect of high exchangeable potassium percentage on soil properties and plant growth

Within the framework of this study, the influence of high exchangeable potassium percent (EPP) on the physical condition of the soil and on growth is evaluated, assuming the possibility of its improving the structure of the soil.