Cation exchange capacity is a commonly used soil chemical property that describes the maximum quantity of cations a soil or substrate can hold while being exchangeable with the soil solution. Cation exchange capacity is often associated with a soil
be neutralized and in the buffering capacity of moss peats. Two factors that may affect the neutralization requirement and buffering capacity of moss peat among batches are cation exchange capacity (CEC) and base saturation [fractional calcium (Ca 2
conducted using Na + as the counter-cation of HCO 3 – , although a lesser number of studies have used K + ( Norvell and Adams, 2006 ). In these studies, the specific toxicity and osmotic effects of Na + have been ignored, probably under the assumption
pH and preventing drift is, therefore, an important aspect of nutrient management. Plants affect root zone pH primarily through differential uptake of cation and anion nutrients ( Haynes, 1990 ; Lea-Cox et al., 1996 ; Marschner, 2012 ; Rengel, 2003
Problems of inconsistent initial pH in peat moss-based substrates that are created using standard formulas for limestone additions, and pH drift from the target in those substrates may be due to variations in the CEC and BS of peat moss. This study was conducted to determine whether such variation exists. Sixty-four peat moss samples were obtained from several bogs across Alberta, Canada. Adsorbed cations on each peat moss sample were displaced with hydrochloric acid (HCl), and flushed out with three deionized water washes. The displacing/flushing solution was collected and later analyzed for concentration of bases (Ca, Mg, K, and Na) using atomic absorption spectrometry. After cations were removed, the peat moss exchange sites were saturated with barium acetate [Ba(OAc)2] to displace the H+, which were then collected by a second flushing with deionized water. This second displacing/flushing solution was titrated with measured amounts of NaOH to a phenolphthalein end point. Base saturation and CEC were calculated. There were significant variations in CEC (ranging from 108.12 to 162.25 cmol·kg-1) and BS (ranging from 13.52% to 63.97% of CEC) among the peat moss samples. Ca accounted for 78.08% of the BS. For a given peat moss, the higher the BS, the lower the neutralization requirement to achieve a target pH. Also, high CEC peat mosses may have greater buffering capacity than those with low CEC, which may result in less pH drift.
Pine bark cation exchange capacity (CEC) (by Ba/Mg exchange on four particle size fractions) increased regularly from 38 to 98 meq/100 g between pH 4 and 7. Decreasing particle size from <2.38 to <0.05 mm did not result in the expected large increases in bark CEC. The Ba/Mg CEC of unsieved bark samples was less than that determined by the weighted average of component size fractions. Monovalent/monovalent-determined CEC was higher than Ba/Mg, indicating that a number of differing charge-specific sites are involved. The pH-dependent CEC increase between pH 4 and 7 was greater for divalent exchange than for monovalent. Ammonium/K CEC was higher than K/NH4 CEC, probably due to enhanced NH4 adsorption by carboxyl groups. Infrared analysis of pine bark revealed that surface functional group composition is similar to soil organic matter. The accurate measurement of CEC in pine bark is complicated by solution pH and ionic strength, as well as by the cations employed for exchange.
The accumulation of cations and NO3-N was higher in cucumber shoots than in pea shoots grown on nitrate nutrition. Total N concn in shoots did not differ between the species. Ammonium nutrition suppressed cation accumulation in cucumbers but not in peas. Differences in cation accumulation in the shoots are attributed to the form in which N is translocated from root to shoot.
Treatment of beet root slices (Beta vulgaris L.) with (2-chloroethyl)phosphonic acid (ethephon) at 100 ppm increased membrane permeability 7-fold as indicated by betacyanin leakage. Leakage was much greater at higher concentrations of ethephon. Divalent and trivalent cations (Ca++, Mg++, La+++) prevented the effects of ethephon on membrane leakage without altering the rate of ethylene evolution. The monovalent cations (K+, Na+, NH4 +) were not effective in relieving the ethephon effect.
The elemental distribution (P, Ca, K, Mg) within inter- and intracellular structure of arbuscular mycorrhizal (AM) cucumber root was determined using energy dispersive X-ray spectroscopy (EDAX). Cucumber (Cucumis sativus cv. Chinesische Schlange) was grown as a test plant using compartmentalized pots with separate zones for hyphal growth and was inoculated or not with the AM fungus, Glomus mosseae (BEG 107). EDAX studies revealed that P in intercellular structures including fungal cells in cucumber root colonized with AM was mainly localized in both polyphosphate granules in arbuscular vacuole and arbuscular cytoplasm. Ca in AM root was mostly localized in cortex cell wall, interfacial apoplast between root and fungus, arbuscular cytoplasm and poly phosphate granules. Mg was distributed homogenously in most cell compartments within AM root while K was localized mainly in cell wall of stele. Higher contents of Ca and Mg were detected in polyphosphate granules whereas lower content of K was detectable. These results indicate that polyphosphate granules could play a role as a complex forming site with metal cations especially with divalent cations like Ca and Mg. In addition, it could give a possibility of regulation function of polyphosphate granules on element transfer from fungus to host plant root. Furthermore, the distribution of element within cortex cytoplasm, interfacial apoplast between plant root and fungus and arbuscular cytoplasm might give a clue on the element transfer mechanism between symbionts.
Queen palms (Syagrus romanzoffiana) were grown in containers of sand to determine the effects of irrigation water salinity and liming rate on cation uptake by the plants. Dolomite was incorporated at rates of 0, 3, or 6 kg/m3. Within each lime rate palms were irrigated with a solution of NaCl and CaCl2 (molar ratio =5Na:1Ca) at conductivities of .25, 1, 2, 4, or 6 dS/m. Plant height and dry weight and leaf Mg were decreased with increasing irrigation water salinity, whereas leaf Ca was increased at higher salinities. Leaf Mn and Zn increased, then decreased as salinity was increased. Leaf Ca and Mg increased with increased lime, but leaf Mn and Cu were decreased by increasing the lime rate. Leaf K increased, then decreased as lime rate was increased.