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1.
Abstract

Concern has been expressed that large amounts of volcanic ash from the May 18, 1980 eruption of Mount St. Helens may have created potential nutritional problems associated with forage production in northern Idaho and eastern Washington to the extent that adjustments need to be made in soil test correlation data. The objectives of this greenhouse study were to: (1) determine the effect of varying amounts of volcanic ash mixed into soils of northern Idaho on total alfalfa biomass production, and (2) to determine the effect of various soil/ash mixtures on the nutrient concentrations of P, K, S, Ca, Mg, Mn and Zn in alfalfa.

Alfalfa was grown in eight different northern Idaho soils amended with differing levels of volcanic ash (0, 20, 35, 50 and 75%) in the greenhouse. The alfalfa seeds were inoculated and fertilizer P and S were added to all treatments. Total plant biomass and P, K, S, Ca, Mg, Mn and Zn plant concentrations were measured.

The eight soils were pooled for analysis and it was found that increasing amounts of volcanic ash increased alfalfa biomass production. Plant P, S, Ca, Mg and Zn concentrations also increased with increasing levels of ash. Conversely, increasing levels of ash resulted in lower alfalfa tissue K and Mn concentrations. There is no evidence to suggest that the highest levels of ash which fell in northern Idaho (700,000 kg/ha) inhibited alfalfa production. Consequently, there is no need for adjustments in soil test calibration data presently used for fertilizer recommendations for alfalfa.  相似文献   

2.
Abstract

Soil test recommendations currently used in Alaska are based on a limited amount of in‐state data along with consideration of data from other states. Recently, Mehlich 3 extractable P has been found to be highly correlated to yield on representative agricultural soils in Alaska. To fully use its multi‐element capability, a study was conducted to correlate Mehlich 3 extractable P and cations (K, Ca, and Mg) with the P and cations extracted by the Bray 1 and ammonium acetate methods respectively.

When Mehlich 3 extractable K and Mg were regressed with ammonium acetate extractable K and Mg respectively, the relationship was essentially one‐to‐one and the relationship held across all soils tested. Significant variation was observed among soils in the extraction of Mehlich 3‐P and Ca relative to Bray 1‐P and ammonium acetate‐Ca. Individual soil character appeared to affect the regressions for extractable P and Ca, even though the R2 values were generally high. The regression slopes for Mehlich 3‐P versus Bray 1‐P ranged from 1.01 to 1.88 with Mehlich 3 extracting an average of 66% more P than Bray 1 in the volcanic ash soils, and 12% more in the loess soils. The regression slopes for Mehlich 3‐Ca versus ammonium acetate‐Ca ranged from 0.95 to 1.33, and the former extracted an average of 17% more Ca than the latter. It is suggested that the regression data of P and Ca can be extrapolated to other soils based on soil classification; to extend the soil test data over a geographic base.  相似文献   

3.
Abstract

Interpretation guidelines for the availability of calcium (Ca), magnesium (Mg), and potassium (K) in soilless media have been developed through plant growth studies and comparisons amongst extractants. The extractants used were 70% ethanol (EtOH), water, DTPA, ammonium acetate (NH4OAc) and silver thiourea (AgTu). Ethanol, which removes ions in pore water, extracted only 4.5, 13, and 26% of the Ca, Mg, and K, respectively, that could be extracted by AgTu from Pinus radiata bark of pH 5.66 and CEC of 11.2 cmol+/L. Acidification to pH 4.62 increased these proportions to 22, 40, and 38%. Correlations between water and DTPA for 39 media were excellent for both individual elements and the ratios Ca/Mg, K/Mg, and Ca, Mg, and K/(the sums of their concentrations in the extractants) (r2 = 0.88–0.98). Correlations between these extractants and AgTu and NH4OAc were poor for individual elements (r2 = 0.37–0.75) but high for ratios (r2 = 0.71–0.96). For Petunia ’Celebrity Salmon’ growing in peat media of similar pH but widely different Ca, Mg, and K proportions, the ratios of these elements in the shoots were highly correlated with their ratios in 2 mM DTPA extracts of the media. Similarly high correlations were obtained between the Ca/Mg ratios of the shoots of three Asplenium species growing in pinebark media and this ratio for DTPA, NH4OAc, and AgTu extracts of the media. The results indicate that the ratios of Ca, Mg, and K to one another in water and DTPA extracts of soilless media are good indicators of the availability of these elements to plants. Healthy specimens of the test plants grew in media whose DTPA extracts had a minimum Ca/Mg mole ratio of 1 or 2, depending on the Ca requirements of the species. The upper limit for good growth was deduced to be about 6. Limits for NH4OAc and AgTu extracts were similar to those found for crop plants in soils, at 1.6 or 3 to about 9. Minimum amounts of Ca, Mg, and K extracted by water and DTPA that were adequate for short‐term growth in the absence of further inputs were about 9,2.5, and 5 cmol+/L medium, respectively, at pH 6.0. The effect of pH on cations removed by water and DTPA raises the minima to about 19, 5, and 7.5 cmol+/L at pH 5.0.  相似文献   

4.
Abstract

A greenhouse experiment was conducted with soils allegedly contaminated with airbourne dust containing Mg and Ca oxides and carbonates to study the growth and composition of corn, orchardgrass, and alfalfa plants. Soils were obtained from sites varying in distance from the alleged source of airbourne dust.

Soil pH values ranged from 6.2 to 8.7. Plant yields decreased only when the soil pH increased above 7.7. There was no apparent relationship between the observed yield decrease and the N, P, K, and B concentrations in the plants. Although the Mn and Zn concentrations generally decreased with increasing soil pH, the decrease was not great enough to account for the yield depressions. The obviously minor symptoms occurring on the plants growing on the most affected soils could not be associated with a deficiency or excess of any other element.

The Ca/Mg ratio in the alfalfa plants decreased as soil pH increased over the range from 6.2 to 8.7. However, the Ca/Mg ratios in the corn and orchardgrass plants decreased only when the soil pH values increased above 7.7. The apparent imbalance of Ca and Mg in the tissues may account for the yield depressions.  相似文献   

5.
Summary

A simple, single‐step extraction with LiEDTA for the estimation of CEC and exchangeable bases in soils has been developed. Multivalent cations are stripped from the soil adsorption sites by the strongly chelating agent EDTA, and are replaced by Li. In soils without CaCO3 or water soluble salts, exchangeable divalent cations (Ca, Mg) are chelated by EDTA and exchangeable monovalent cations (Na, K) are replaced in a single extraction step using 0.25–2.5 g of soil and 10.0 ml of extractant.

In calcareous soils the CEC can be determined in the same way, but for the extraction of exchangeable Ca and Mg, another separate extraction is needed because dissolution of calcite by EDTA is unavoidable. This extraction is done with as much NaEDTA as needed to extract only exchangeable Ca and Mg in a 1:2 (m/V) soil/alkaline‐50% (V/V) aethanolic solution to minimize dissolution of calcite.

In gypsiferous soils gypsum is transformed into insoluble BaSO4 and soluble CaEDTA by LiBaEDTA thus avoiding interference of Ca from dissolution of gypsum, which renders the traditional methods for determining CEC unsuitable for such soils. To determine exchangeable Ca and Mg, Na4EDTA is used as for calcareous soils.

In saline/sodic soils replacement of Na by Li is incomplete but the Na/Li‐ratio at the complex after extraction is proportional to the molar Na/Li‐ratio in the extracts, so that the CEC and original exchangeable sodium (ESP) content can be calculated. Additional analysis of Cl and, if necessary, SO4 in the extracts of saline soils can be used to correct for the effect of dissolution of the salts on the sum of exchangeable cations.

This new method is as convenient as the recently developed AgTU (silverthiourea), but is better suitable for calcareous and gypsiferous soils.  相似文献   

6.
Abstract

An experiment was carried under controlled conditions to investigate the influence of the anions, H2PO4 ‐. and Cl on the ionic equilibria, selectivity and effective diffusion of Rb, K, Na, Ca, Mg in two Indiana soils.

Additon of anions to the soils increased the concentration of cations in soil solution. In both the soils receiving H2PO4 ‐, lower cation concentrations were found in the soil solution than in those receiving Cl‐ . Additon of H2PO4 ‐and Cl‐ reduced the ion selectivity coefficient, k, for various homovalent (Rb/K, Rb/Na, K/Na, Ca/Mg) and mono‐divalent ion pairs (Rb/Ca, Rb/Mg, K/Ca, K/Mg). In Zanesville soil treatments receiving H2PO4 ‐ had lower k values for mono‐divalent cations than treatments receiving Cl‐. However, no such conclusions could be drawn for Raub soil. Soils treated with H2PO4 ‐ had higher k values for homovalent cations than Cl‐ treated soils. The differences in the selectivity of adsorption in these two soils might be attributable to the differences in the type and nature of exchange materials and cation concentrations on the exchange phase.

Addition of H2PO4 ‐ or Cl‐ enhanced the magnitude of effective diffusion coefficient. (De) of all the cations under considerations. The magnitude of effective diffusion coefficient for cations was lower for H2PO4 ‐ treated soils than Cl‐ treated soils. Such a reduction in De is related to the reduction in cation concentration in soil solution thereby increasing the buffer capacity for the ions under consideration.  相似文献   

7.
Abstract

The ability of poultry litter to support plant growth by supplying essential plant nutrients in the absence of other sources of the nutrients has not been studied thoroughly. The objectives of this research were to (1) determine the ability of poultry litter, as the sole nutrient source, to provide macronutrients and support growth of cotton (Gossypium hirsutum L.) (2) evaluate the distribution of these nutrients within the different plant parts, and (3) estimate the efficiency with which these nutrients are extracted by cotton. The research was conducted in plastic containers filled with a 2:1 (v/v) sand:vermiculite growing mix under greenhouse conditions. The treatments included broiler litter rates of 0, 30, 60, 90, or 120 g pot?1 with or without supplemental Hoagland's nutrient solution. Broiler litter supplied adequate amounts of the macronutrients nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) and supported normal growth of cotton. Tissue nutrient analysis showed that the concentration of N, P, K, and Mg in the upper mainstem leaves was within published sufficiency ranges for cotton growth. Evaluation of the N distribution indicated that the cotton plant partitions N to reproductive parts when faced with deficiency of this nutrient and favors allocating N to new leaf growth once the requirement for reproductive growth is met. The partitioning of P was similar to that of N but less distinct. Cotton extracted Mg and K with greater efficiency (up to 58%) than the other nutrients and stored these nutrients in older leaves. The extraction efficiency of N ranged between 21% at 120 g pot?1 litter and 27% at 30 g pot?1 litter. Phosphorus was the most poorly extracted nutrient, with only 16% of the total applied P extracted when 30 g pot?1 litter was applied and only 6% extracted at the higher litter rates. This suggests that the same problem of P buildup that has been reported in soils under pasture may also occur when poultry litter is repeatedly applied to the same soil planted to cotton. These results show that broiler litter not only supplied enough N but also supplied the four other macronutrients (P, K, Ca, and Mg) in amounts sufficient to support normal cotton growth. This research implies that poultry litter can effectively substitute for several fertilizers to meet crop macronutrient (N, P, K, Ca, and Mg) needs in soils deficient in any or all of these nutrients.  相似文献   

8.
A Method for the Determination of Exchangeable Cations in Forest Soils A simple extraction method with NH4Cl was developed for determining exchangeable cations in forest soils. The influence of selected parameters (reaction time, concentration of NH4Cl, filter medium etc.) affecting the amount of extractable cations was tested and a standardisation was done. The cation exchange was completed in less than 4 h. For a quantitative extraction of K, Mg, Ca, and Mn a concentration of 0.05 M NH4Cl was sufficient. The extractable amount of these cations was always clearly defined. However, extracted Al and Fe increased with the NH4Cl-concentration. Depending on the soil samples, the exchange is not quantitative even when using a saturated solution. The extractable H+ is nearly independent of the NH4Cl-concentration. Probably considerable amounts are dissociated from organic acids. The optimized method is feasible and can be used for K, Mg, Ca, and Mn as an alternative to percolation methods.  相似文献   

9.
Simultaneous multi-element extraction has been increasing worldwide to improve soil laboratory testing quality and effciency. This study sought to investigate the applicability of the Mehlich-1, Mehlich-3, and resin methods for simultaneous extraction of soil available P, K, Ca, and Mg as well as the effect of using conversion equations on nutrient recommendations for crops. Topsoil (0-20 cm) samples were taken from the most representative soil types used for crop production in southern Brazil with a wide range of chemical, physical, and mineralogical properties. Soil P, K, Ca, and Mg were simultaneously extracted using 1.0 mol L-1 KCl, Mehlich-1 and Mehlich-3 solutions, and membrane resin. The amounts of P extracted with the Mehlich-1 method were, on average, 50% lower than those extracted with the resin and Mehlich-3 methods. However, the resin method extracted the lowest amounts of K, Ca, and Mg. The use of conversion equations was suitable and it did not a?ect negatively the K recommendations for crops grown on soils of southern Brazil.  相似文献   

10.
Abstract

Electro‐ultrafiltration (EUF) of soils ‐ a combination of electrodialysis and ultrafiltration ‐ which works on the principle of extraction of nutrient ions from soils under an external electric field, can be employed as a useful method in soil fertility work to characterize the desorption parameters of soil nutrients.

With a view to improving the efficiency of extraction of Mg, but mainly to prevent the precipitation of Mg(OH)2 in the membrane separating the soil suspension from the cathode 0.05 M H3BO3, was used instead of distilled water in the EUF analysis of pure Mg solutions and different soils. The recovery of Mg from solutions was improved by using boric acid. But the objective of preventing the deposition of Mg(OH)2 in the membrane was not fully achieved. With soils the desorption characteristics of K, Ca and Mg were appreciably affected. The addition of boric acid enhanced the desorption rate for all three elements; the most for Ca and the least for K. The effect of boric acid on the precipitation of Mg(OH)2 in the membrane was not straightforward. Only in two cases a reduction was achieved.  相似文献   

11.
Abstract

An established stand of alfalfa was fertilized with different combinations of N, P and K. The rate used per nutrient was constant for all combinations. The study was conducted to evaluate the effect of fertilizer application, diurnal change and period to period fluctuation on the mineral composition of alfalfa. Two experiments were conducted at different stages of morphological maturity. Experiment one (E‐1) was initiated when regrowth after an initial hay harvest was in the late‐vegetative to early‐bud stage. The second experiment (E‐2) was initiated when regrowth from E‐1 was approximately 20 cm tall.

Phosphorus application significantly increased the P concentrations in alfalfa, but decreased the Cu levels in both experiments. Potassium applications significantly decreased the levels of Ca, Mg, Na, Cu, Zn, Mo and Co.

Levels of all minerals analyzed in E‐1 were significantly different from period to period while only seven of the sixteen were significantly changed in E‐2. Period to period differences were partially explained by rainfall pattern.

Significant diurnal variations were found for K, Ca, Mn, B, Sr, and Zn in E‐1 and for Ca, SiO2, and Sr in E‐2.

The N, P, and K applied and the P and K available in the soil were correlated with cation levels in alfalfa and the interrelationships were discussed.  相似文献   

12.
Abstract

The objective of this research was to compare the results from anion exchange Resin extraction of P, and the acidified ammonium acetate (AA) extraction of K and Mg with the results obtained using two single extraction procedures, Mehlich 1 (M‐l) and Mehlich 3 (M‐3). Phosphorus extracted from 72 Zimbabwe soils using M‐l and M‐3 was comparable to Resin extracted P in about 80% of the soils. Mehlich 1 extracted about half the amount of P as the Resin method, and M‐3 extracted about one and one‐half times as much. Phosphorus by M‐3 was highly correlated, (r — 0.846), with Resin extracted P from soils having 0.01M CaCl2 pH values of equal to or greater than 5.9. On soils less than pH 5.9, the r value was 0.502, and for all soils, the r value for M‐3 vs Resin P was 0.615. Mehlich 1 extracted P vs Resin P had a r value of 0.298. Acidified ammonium acetate (AA) extraction of K and Mg was comparable to M‐l and M‐3 extraction of K and Mg in 92% or more of the 72 soils. The K correlation coefficient (r) for AA vs M‐l and AA vs M‐3 was 0.918 and 0.944, respectively. The Mg correlation coefficient (r) for AA vs M‐l and AA vs M‐3 was 0.940 and 0.962, respectively.  相似文献   

13.
Abstract

For Southeastern forest soils amounts of P, K, Ca, Mg, and Mn extracted by 0.05 N HCl + 0.025 N H2SO4 (double‐acid) were significantly correlated with amounts extracted by 0.2 N NH4Cl + 0.2 N HOAc + 0.015 N + NH4F + 0.012 N HCl (new‐Mehlich). The new‐Mehlich consistently removed more nutrients than the double acid.

Both P and Mn extracted by the two solutions were significantly correlated with their concentrations in the foliage of loblolly pine (Pinus taeda L.).  相似文献   

14.
Abstract

Magnesium deficiency in corn (Zea mays L.) is often attributed to the low levels of Mg in soils. This study was conducted to determine elemental and/or cation balance efficiency of corn hybrids grown on a soil low in available Mg, Among the 15 hybrids tested, no differential efficiency in ear leaf concentration of P was found at two planting dates. Leaf concentrations of Zn and Fe were influenced by planting date for all hybrids but interactions between hybrids and planting date were found only for K, Ca, Mg concentrations and the sum of the Meq Ca + Mg/100 g, the Meq K + Ca + Mg/100 g, and the K/Ca and K/Ca + Mg ratios. Planting dates did not Influence the K/Mg ratio among hybrids. Large differences in efficiency of K, Ca, and Mg were found but these cations were found to have large Interactions. Data show that Ca and Mg efficient hybrids are less efficient in K than Ca and Mg inefficient hybrids. It should be possible to breed corn hybrids for better cation balance efficiency for use on infertile soils low in avallable Mg.  相似文献   

15.
Twenty surface soils from four main Soil Groups in Malawi and their sub-soils were divided into three groups based on cation exchange capacity (group I, CEC < 50; group II, 50–100; and group III > 100μeq g–1). In each soil group the maximum amounts of K removed by successive extraction with 0.005 M CaCl2 solution were well related to the potassium potential pK–0.5p(Ca + Mg), exchangeable K, ‘step K’, and the quotient ‘step K’/CR.K, where CR.K is ‘constant-rate’potassium. In Group III soils only, ‘step K’/CR.K values were significantly correlated with pH, clay, and CEC, and this suggested that the soils were relatively rich in K+ specific binding sites. In 27 soils from an NPK factorial experiment on tea, the rate of depletion of extractable K reserve increased with ammonium sulphate treatment, whereas K fertilizers tended to off-set significantly (P= 0.001) the depletion of K reserve. The values for the change in free energy ΔG =RT In aK/ (a(Ca+Mg)) ½, ranged from –12 to –16 kJ mol–1, and field observations showed that tea plants growing on soils having ΔG values less than –15 kJ mol–1 responded to K fertilizers. The investigation has indicated that heavily cropped soils are likely to show crop responses if the intensive cropping system does not include supplementation of K.  相似文献   

16.
Abstract

An established stand of Ranger alfalfa was topdressed with equal rates, but different combinations, of N, P, and K. Five harvests were taken and the material analyzed for cation concentrations.

Phosphorus application significantly increased P concentrations in alfalfa, but had little influence on concentration of other ions. Potassium applications showed striking effects by significantly increasing K levels of the forage while decreasing Ca, Mg, Cu, Zn, Al, and Mo levels.

Significant differences occurred among harvest dates for 14 of the 16 cations analyzed. Seasonal trends were evident for SiO2, Zn, Al, Co, and Na.

Applied N, P, and K and available soil P and K were associated with cation concentration of alfalfa and these interrelationships are discussed.  相似文献   

17.
Abstract

Forage intake with potassium/(calcium + magnesium) [K/(Mg + Ca)] values in excess of 2.2 are associated with grass tetany and Mg deficiencies in ruminants. This study was conducted to determine the degree to which forage K and Mg concentrations and K/(Ca + Mg) ratios could be predicted from soil bicarbonate (HCO3) extractable phosphate‐phosphorus (PO4‐P), and saturation extract Ca, Mg, K, sodium (Na), and nitrate‐nitrogen (NO3‐N) concentrations. Crested wheatgrass (Agropyron spp) strains and cultivars representing four ploidy levels were grown in the greenhouse on eight calcareous soils with different saturation extract Ca, Mg, K and K/Mg ratios. The plants were harvested three times. Soil solution K/(Ca + Mg) and K/Mg ratios were the only measured soil parameters that showed a consistent correlation with plant K/(Ca + Mg) ratios. Bicarbonate extractable soil P was positively related to plant P and K uptake in the first harvest, but was not related in the second and third harvests nor was soil P related to plant Ca or Mg content. There was a tendency for the higher ploidy level entries to have higher plant K/(Ca + Mg) ratios. It was concluded that soil K/(Ca + Mg) ratios can be used to predict relative forage K/(Ca + Mg) ratios for grasses grown under similar conditions.  相似文献   

18.
Abstract

The effects of irrigating with saline water on native soil fertility and nutrient relationships are not well understood. In a laboratory experiment, we determined the extent of indigenous nutrient [calcium (Ca), magnesium (Mg), potassium (K), manganese (Mn), and zinc (Zn)] release in salt-saturated soils. Soils were saturated with 0, 75, and 150 mmolc L?1 sodium chloride (NaCl) solution and incubated for 1, 5, 10, and 15 days. The saturation extracts were analyzed for pH, ECe, and water‐soluble Ca, Mg, K, Mn, and Zn, and the remainder soil samples were analyzed for exchangeable forms of these elements. In a subexperiment, three soil types (masa, red‐yellow, and andosol) were saturated individually either with 100 mmolc L?1 of NaCl, sodium nitrate (NaNO3), or sodium sulfate (Na2SO4) salt. These salts were also compared for nutrient release. Soils treated with NaCl released higher amounts of water‐soluble than exchangeable nutrients. Except for Zn, the average concentrations of these nutrients in the soil solution increased significantly with time of incubation, but concentrations of the exchangeable forms varied inversely with time of incubation. The masa soil exhibited the highest concentrations of Ca and Mg, whereas K was highest in andosol. The extract from soils treated with NaCl contained greater amounts of soluble cations, whereas soils treated with Na2SO4 produced the lowest concentration of these elements irrespective of the type of soil used.  相似文献   

19.
Abstract

Three different chemical extractants were evaluated as to their extraction efficiency for copper (Cu), zinc (Zn), lead (Pb), aluminium (Al), iron (Fe), chromium (Cr), manganese (Mn), potassium (K), magnesium (Mg), and calcium (Ca) on forest soil profiles from the Romanian Carpathians. The extractants were hot 14 M nitric acid (HNO3), 0.05 M hydrochloric acid (HCl), and 0.1 M sodium pyrophosphate. By comparing amounts extracted by 0.05 M HCl and 0.1 M sodium pyrophosphate relative to that dissolved by hot 14 M HNO3, some conclusions were drawn concerning the chemical forms of the metals in the extractable pool. The amount released by 0.05 M HCl was generally less than 10% of the HNO3‐extractable fraction but showed considerable variation among the elements studied. The relative amount extracted by pyrophosphate increased with organic‐matter content of the soils for Cu, Zn, Pb, Al, Fe, and Cr; stayed more or less constant for Mn, K, and Mg; and decreased for Ca. These findings are discussed with respect to the different binding forms of the metals in the soil and the processes affecting their mobility. From the present results, the metals were ranked as follows with respect to their ability to form organic complexes in natural soils: Cu>Cr, Pb>Ca>Al>Fe, Zn, Mn, K>Mg. However, the use of cold dilute HCl as a fractionation step may be questionable in cases of soils with a high content of substances possessing large neutralization capacity for protons.  相似文献   

20.
Abstract

The relationship between water soluble and exchangeable cations (Ca, Mg, Na, and K) was investigated for surface horizons of 195 soils including many taxonomic categories and a wide range in physical and chemical properties from around the world. This will provide information on exchangeable soil cation solubility for use in estimating plant uptake and leaching potential. Amounts of water soluble and exchangeable cations were not consistently related (r2 of 0.50, 0.08, 0.77, and 0.49 for Ca, Mg, Na, and K). High correlations were biased by high water soluble and exchangeable cation levels of a few soils that had 3.8‐ and 2.5‐fold greater mean than median values. The ratio of exchangeable to water soluble cations was closely related to cation saturation (r2 of 0.87, 0.95, 0.95, and 0.93 for Ca, Mg, Na, and K, respectively). As the degree of saturation of the exchange complex by a certain cation increased, solubility Increased. A change in saturation had less effect on K than on Na, Mg, and Ca solubility. Only exchangeable soil cations (NH4OAc extractable) are routinely measured and reported in soil survey reports, thus, water soluble levels may be determined from cation saturation. This will allow estimation of the amounts of cation that can potentially move in solution through the soil or be taken up by plants. Use of cation saturation, in addition to exchangeable content, will better characterize soil cation availability by representing quantity, intensity, and buffer factors.  相似文献   

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