Increase In Exchangeable Ca Research Articles

Assessment of selected soil physicochemical properties on different land-use systems and landscape positions at Hamesa watershed, Wolayita zone, Southern Ethiopia

The investigation was undertaken at Hamesa watershed of Wolayita Zone with the aim to assess the consequences of land-use systems and topography on the physical and chemical properties of selected soils. Surface soil samples taken at 0-15 and 15-30 cm depths from three land-use systems (enset, grassland and maize fields) were collected under three slope positions (upper, middle and lower). Both the clay and bulk density increased with depth, while total nitrogen (N), OC, available P and micro-nutrients (Fe, Zn, Mn, and Cu) decreased. On the landscape positions, increase in exchangeable Ca and K, pH, bulk density and available Mn down the slope was observed; whereas total N, OC, available P and available Fe showed decreasing trend down the slope. At 0-15 cm soil depth, grassland soils exhibited higher bulk density and lower porosity as a result of livestock movement which was compacted. Grasslands had higher OC and TN compared to the other two land-use systems, due to the accumulation of humus in the root system in the grassland. Application of household refuses and manure contribute to increasing available P, TN, Zn, Ca and K contents in enset farmland. On the contrary, maize land use had lower CEC, K, PBS, Mg, TN and OC, which might be due to crop removal, erosion phenomena, and excessive tillage activities. These results suggest that for sustainable crop production, proper management practices should be in place by considering different slope positions and land-use systems. Key words: Land use system, slope position, physical, chemical soil properties.

Long-Term Effects of Forest Liming on Soil, Soil Leachate, and Foliage Chemistry in Northern Pennsylvania

Sugar maple (Acer saccharum Marsh.) decline disease, decreased growth, and regeneration failure have been related to a low supply of Ca and Mg. There is increased interest in augmenting cation availability via liming, but there is little information on the amounts of lime required and the longevity of the lime treatment. A single application of 22.4 Mg ha-1 of dolomitic limestone in 1985 at four forested sites in Potter County, PA has shown that soil, soil water, and sugar maple foliage chemistry are significantly altered by liming and the changes in soils and foliage persist as long as 21-yr post-treatment. By 2001, only 3 kg ha-1 of lime remained undissolved while increases in exchangeable Ca and Mg, and pH continued through 2006 at depths up to 35 to 45 cm. Exchangeable Mn and Al concentrations were significantly reduced by lime application, though effects were slower to develop at deeper depths. Soil solution chemistry from 1996 was highly variable but reflected the changed soil nutrients. On limed plots, sugar maple foliage had elevated concentrations of Ca and Mg in 2006 samples, indicating the persistence of the lime treatment. Comparison of Ca/Al ratios in soil solution, soils, and foliage show inconsistencies from previous published risk thresholds. Species-specific thresholds of Ca and Mg availability in soil and foliage have better potential management application and should be more rigorously tested as stress indicators.

N2 fixation by faba bean (Vicia faba L.) in a gypsum-amended sodic soil

The response of faba bean to the application of four rates of gypsum (0, 2.5, 5.0, 10.0 t ha−1) to a non-saline, alkaline sodic soil was measured in terms of grain yield, dry matter (DM) production, N accumulation and the proportional dependence of the legume on symbiotic N2 fixation (Patm). A yield-independent, time-integrated 15N-dilution model was used to estimate symbiotic dependence. A significant decrease in the exchangeable sodium percentage and significant increases in exchangeable Ca++ and the Ca++:Mg++ ratio in the 0–10-cm soil layer were measured 30 months after application of 10 t ha−1 gypsum. Despite low and erratic rainfall during crop growth, faba bean DM and N uptake responded positively to gypsum application. The symbiotic dependence of the legume at physiological maturity was little affected by sodicity (Patm = 0.74 at zero gypsum and 0.81–0.82 at 2.5–10 t ha−1 gypsum). The increase in fixed N due to gypsum application was mainly due to increases in legume DM and total N uptake. At 10 t ha−1 of gypsum, faba bean fixed more than 200 kg N ha−1 in above-ground biomass.

Upper Profile Changes Over Time in an Appalachian Hayfield Soil Amended with Coal Combustion By‐products

Large amounts of flue gas desulfurization (FGD) and fluidized bed combustion (FBC) by‐products from burning coal, consisting primarily of gypsum, are available for potential use as a soil amendment. However, information is limited on longer‐term changes in chemical and physical properties induced over time and over small depth increments of the upper soil profile after applying these amendments. This study examined longer‐term effects in an abandoned Appalachian pasture soil amended with various liming materials and coal combustion by‐products (CCBPs). Soil chemical and physical properties were investigated over time and depths. The results indicated limited dissolution and movement of the calcium (Ca) and magnesium (Mg) applied with the chemical amendments, except for Ca and Mg associated with sulfate. However, sufficient dissolution occurred to cause significant increases in exchangeable Ca and Mg and decreases in exchangeable Al that were reflected in corresponding increases in soil pH. These beneficial effects persisted over time and were confined to the upper 0‐ to 15‐cm depth of the profile. The greatest benefits appeared to be in the upper 0‐ to 5‐cm surface layer. Both Ca and Mg applied as calcitic dolomitic limestone tended to be immobilized in the upper 0‐ to 5‐cm layer of the soil profile; Ca more so than Mg. The presence of S applied in the FGD and FBC amendments appeared to enhance the mobility of Ca and Mg. The ratio of Ca/Mg in HCI extracts from the calcitic dolomitic treatment was close to that of applied calcitic dolomite, implying that the inactive component in soil might be the original calcitic dolomite particles. Soil physical properties measured over small depth increments showed that application of the amendments improved the saturated hydraulic conductivity only in the upper 0‐ to 5‐cm depth and had little or no significant effect on the dry bulk density and plant‐available water.

Retention of Ca and Mg in the forest floor of a spruce stand after application of various liming materials

In a forest stand lime is commonly applied to the forest floor to neutralize acidity and to improve buffering capacity of soil by the addition of carbonate and other anions of weak acids. This is expected to cause major chemical changes in the forest floor. In this study, different liming materials, equivalent to 60 kmol c Ca 2++Mg 2+ ha −1, were applied to the forest floor of a spruce stand. The limes were dolomite, mixtures of dolomite and calcite or chalk, and silicate industrial slag lime (‘Hüttenkalk’) of varying particle size combinations. Two years after lime application, salt extractable Ca 2+ and Mg 2+ was measured in the forest floor using a sequential percolation method. This method allowed the assessment of Ca 2++Mg 2+ present on exchange sites by distinguishing between the amounts released upon dissolution of residual, undissolved liming material. In all cases there were major changes in exchangeable content of Ca 2+ and Mg 2+ in the L+F layer, whereas changes in the H layer were small. Differences in the effects of liming materials on the litter layer were attributed to their texture, the contents of Ca 2+ and Mg 2+ and the associated anion (carbonate or silicate). High content of exchangeable Ca 2+ and Mg 2+ was observed in the forest floor when liming materials were of high Ca and Mg content and of fine texture. The sum of exchangeable Ca 2++Mg 2+ in the forest floor increased from 7 kmol c ha −1 (control) to 17–26 kmol c ha −1 after liming and accounted for 15.5–31.5% of Ca+Mg applied. This increase in exchangeable Ca 2+ and Mg 2+ of L+F layer indicates large amounts of lime may be required to ameliorate mineral soil at depth, and that the content of these cations will partly determine future lime requirement of the spruce stands.

Amending highly weathered soils with finely ground basalt rock

Surface (0–10 cm) samples of 7 soils from tropical coastal Queensland were incubated at room temperature and at field capacity with finely ground (<150 μ) basalt rock for 3 months. The amendment was applied at 0, 1, 5, 25 and 50 t/ha to cover situations of moderate application rates to that where the amendment might be banded to produce high local concentrations. Having an abrasion pH of about 9, the amendment was able to reduce both active acidity (as estimated by an increase in soil pH) and reserve acidity (reduction in % Al saturation of the CEC). Increases in soil pH resulted in increased CEC, depending on the variable charge nature of each soil, accompanied by increases in exchangeable Ca, Mg, and K supplied by the basalt. The amounts of basic cations converted to exchangeable form constituted only a fraction of the amounts applied. Thus the cations held in reserve ensure that the effect of cation enrichment will be prolonged. In some soils phosphate sorption was significantly reduced by crushed basalt application. Furthermore, ‘available’ P as measured by extraction with 0.005 M H 2SO 4 was increased. These effects appear to be due to the release of silicate from the basalt as well as modest amounts of phosphate in the rock. Three extractants commonly used for estimating Si availability in sugarcane production indicated that all 7 soils contained sub-optimal levels of the element. Application of crushed basalt rock increased extractable Si levels above what is considered sufficient for this crop. The incubated soils were placed in columns and leached with the equivalent of 2750-mm (average wet season) rainfall. Re-analysis showed that the favourable chemical soil properties imparted by the amendment were retained. These results add further support to the contention that the effects of amelioration will continue for some time.

Fifteen-year Change in Forest Floor Organic and Element Content and Cycling at the Turkey Lakes Watershed

To assess the long-term effects of atmospheric deposition on forest floor chemical composition, we took quantitative samplings of L-(Oi), F-(Oe), and H-(Oa) layers at an old-growth sugar maple-yellow birch stand on a till soil at the Turkey Lakes Watershed near Lake Superior, Ontario, Canada, in 1981 and 1996. We then assessed these samples for contents of organic matter (OM), total N, K, Ca, Mg, S, and Na, and exchangeable NH 4 + , NO 3 - , K + , Ca 2+ , Mg 2+ , SO 4 2- , and Na + . Over the 15-year period, total OM and element contents remained unchanged, with the exception of N, which increased significantly from 61.3 kmol/ha in 1981 to 78.4 kmol/ha in 1996. On an area basis, there were significant increases in exchangeable Ca 2+ (from 3.8 to 4.6 kmol/ha) and Na + (from 0.05 to 0.08 kmol/ha) and decreases in exchangeable NH 4 + -N (from 1.41 to 0.95 kmol/ha) and SO 4 2- -S (from 1.29 to 0.96 kmol/ha). There were no significant differences in average annual litterfall OM, N, Ca, Mg, S or Na inputs between 1980 and 1985 and between 1992 and 1997. Average annual wet-only SO 4 2- -S deposition during 1981-86 was 0.30; during 1992-97, it was 0.21 kmol/ha. Annual wet-only NO 3 - -N averaged 0.33 kmol/ha during 1981-86 and was similar during 1992-97. Throughfall was less rich in SO 4 2- and Ca 2+ , Mg 2+ , and Na + during 1992-97 than earlier. Throughfall NH 4 - and NO 3 - fluxes were unchanged. Efflux of cations from the forest floor reflected reduced throughput of SO 4 2- . Overall, the results suggest that in spite of atmospheric inputs, active biological processes-including litter input, fine-root turnover, and tree uptake-serve to impart stability to the mineral composition of mature sugar maple forest floor.

Effect of slaked lime and gypsum on acidity alleviation and nutrient leaching in an acid soil from Southern China

A soil column experiment was made to study the effects of slaked lime (Ca(OH)2) and gypsum (CaSO4·2H2O) on soil acidity, soil solution chemistry and nutrient leaching in an acid soil from Southern China. Results showed that application of sufficient slaked lime to initially increase the pH of the topsoil by 1 unit caused an increase in pH to 5 cm deeper than the layer of application as a result of bicarbonate leaching. With leaching of Ca from slaked lime or gypsum from the topsoil to the subsoil there was a decrease in exchangeable Al in the subsoil. Surface application of slaked lime or gypsum or both decreased the activity of toxic Al and increased AlSO4+ activity in the subsoil solution. The Ca added in slaked lime or gypsum was accounted for by the increase in exchangeable Ca over the soil profile and the leaching loss. By contrast there was a negative balance of extractable sulfate and aluminum in the soil, indicating the formation of precipitates. There was little mineralisation of N and formation of NO3- under the conditions of the experiment. The leaching of cations in this soil treated with slaked lime or gypsum was driven by the dynamics of sulfate.

CANOPY TREE–SOIL INTERACTIONS WITHIN TEMPERATE FORESTS: SPECIES EFFECTS ON pH AND CATIONS

We quantified soil acidity and exchangeable cations in the forest floor and upper 7.5 cm of mineral soil beneath the canopies of individual trees of six different species in a mixed-species forest in northwestern Connecticut. Soil pH decreased in a sequence starting with sugar maple (Acer saccharum) > white ash (Fraxinus americana) > red maple (Acer rubrum) > beech (Fagus grandifolia) > red oak (Quercus rubra) > eastern hemlock (Tsuga canadensis). The differences among species were largest in the forest floor and the top 7.5 cm of mineral soil. Exchangeable Ca and Mg in the 0–7.5 cm mineral soil layer were significantly higher beneath sugar maple than all other species, with the exception of white ash. There were negligible differences among species in the quantity of exchangeable Ca and Mg in the forest floor. In the 0–7.5 cm mineral soil layer, exchangeable Ca was positively correlated with the content of unweathered Ca in the parent material, but the relationship differed among species. There was a large increase in exchangeable Ca in the soils beneath sugar maple but a negligible increase in the soils beneath hemlock and red maple. Exchangeable Al and Fe were highest beneath hemlock and lowest beneath sugar maple. The differences in pH and exchangeable cations between sugar maple and hemlock are likely due to interspecific differences in the introduction of acidity (e.g., organic acids) and Ca uptake and allocation. Observing an association between tree species and specific soil chemical properties within mixed-species stands implies that changes in the distribution and abundance of tree species alters the spatial and temporal pattern of soil acidity and cation cycling in this forest.

Factors Affecting Phosphate Rock Dissolution in Acid Soil Amended with Liming Materials and Cellulose

AbstractCoal combustion by‐product (CCBP; a wallboard‐quality gypsum), limestone, and cellulose had been found to influence the dissolution of North Carolina phosphate rock (NCPR) in an acid Lily loam soil (fine‐loamy, siliceous, mesic Typic Hapludult). Laboratory and incubation experiments were carried out in this study to elucidate the mechanisms responsible for the reduced dissolution of NCPR from CCBP application. The major factors responsible for the reduced PR dissolution were (i) an increase in exchangeable Ca + Mg derived from the CCBP, (ii) an increase in soil pH from the small amounts of CaCO3 in the CCBP material; and (iii) sulfate released from the CCBP resulting in a decrease in P sorption capacity of the amended soil due to competitive sorption between sulfate and phosphate. The further reduction in NCPR dissolution by limestone addition was probably due to the increase in pH and exchangeable Ca relative to CCBP application alone. An increased NCPR dissolution from cellulose addition probably reflected an accelerated depletion of labile P by the cellulose‐induced microbial growth and, hence, biomass production. The four kinetic dissolution parameters, i.e., the half‐life (t1/2) from a first‐order rate equation, the initial dissolution rate‐ and the average dissolution rate‐related constants (A and b) from an Elovich equation, and the potential maximum dissolution of phosphate rock from a Langmuir equation were significantly correlated with pH, the content of exchangeable (Ca + Mg), and P sorption capacity of the CCBP‐amended soil. The t1/2 and A of NCPR in the acid soil could be predicted with 95% confidence by the three soil variables, i.e., soil pH, P sorption capacity, and exchangeable (Ca + Mg). Both t1/2 and A could serve as an indicator of the NCPR dissolution potential in soils.

Base cation biogeochemistry and weathering under oak and pine: a controlled long-term experiment

Large earthen-walled lysimeters at the San Dimas Experimental Forest in southern California present a unique opportunity to assess vegetation effects on biogeochemical processes and cation release by weathering in controlled soil-vegetation systems where archived samples of soil parent material are available for comparison. The lysimeters were filled in 1937 with homogenized fine sandy loam derived on site from the weathering of diorite, and planted in 1946 with scrub oak (Quercus dumosa) and Coulter pine (Pinus coulteri). Changes in base cation contents were measured in above-ground biomass, and total and exchangeable soil pools to a depth of 1 meter. All cations in the non-exchangeable soil pool decreased relative to the initial fill material, indicating release by weathering. Sodium and K were depleted from both exchangeable and non-exchangeable pools of the soils. Plant uptake of Na was minimal, whereas K storage in vegetation exceeded the loss from the exchangeable soil pool. In both soil-vegetation systems, but especially for oak, there was an increase in exchangeable Ca and Mg. For all base cations, storage in above-ground biomass was greater for oak, whereas losses by weathering from the non-exchangeable soil pool were greater under pine. Strong evidence supports biocycling as a controlling mechanism resulting in greater Ca and Mg release by weathering under pine. In addition, decreases in non-exchangeable Ca and Mg were strongly correlated to decrease in Si under oak, whereas no correlation was observed under pine. We conclude that weathering reactions or stoichiometry differed between vegetation types.

Factors Affecting Phosphate Rock Dissolution in Acid Soil Amended with Liming Materials and Cellulose

AbstractCoal combustion by‐product (CCBP; a wallboard‐quality gypsum), limestone, and cellulose had been found to influence the dissolution of North Carolina phosphate rock (NCPR) in an acid Lily loam soil (fine‐loamy, siliceous, mesic Typic Hapludult). Laboratory and incubation experiments were carried out in this study to elucidate the mechanisms responsible for the reduced dissolution of NCPR from CCBP application. The major factors responsible for the reduced PR dissolution were (i) an increase in exchangeable Ca + Mg derived from the CCBP, (ii) an increase in soil pH from the small amounts of CaCO3 in the CCBP material; and (iii) sulfate released from the CCBP resulting in a decrease in P sorption capacity of the amended soil due to competitive sorption between sulfate and phosphate. The further reduction in NCPR dissolution by limestone addition was probably due to the increase in pH and exchangeable Ca relative to CCBP application alone. An increased NCPR dissolution from cellulose addition probably reflected an accelerated depletion of labile P by the cellulose‐induced microbial growth and, hence, biomass production. The four kinetic dissolution parameters, i.e., the half‐life (t1/2) from a first‐order rate equation, the initial dissolution rate‐ and the average dissolution rate‐related constants (A and b) from an Elovich equation, and the potential maximum dissolution of phosphate rock from a Langmuir equation were significantly correlated with pH, the content of exchangeable (Ca + Mg), and P sorption capacity of the CCBP‐amended soil. The t1/2 and A of NCPR in the acid soil could be predicted with 95% confidence by the three soil variables, i.e, soil pH, P sorption capacity, and exchangeable (Ca + Mg). Both t1/2 and A could serve as an indicator of the NCPR dissolution potential in soils.

Downward effects of dolomite and kieserite on two acid soils differing in their organic carbon content

Mg application proved to be a valuable tool for the revitilization and restabilization of declining forest ecosystems growing on acid soils. Adequate fertilization however still requires clear understanding of the downward effects associated with Mg-fertilizers. To that purpose, leaching experiments with Mg solutions were performed in laboratory columns filled with two types of acid soil materials differing largely by their organic carbon content : 80.2 g C kg-1 for soil A and 8.1 g C kg-1 for soil B. Magnesium was supplied either as a solution saturated in dolomite or as a pulse of kieserite solution. The columns were dismantled for analysis after 8, 16, 24, and 32 d. leaching. Dolomite increased soil pH and diminished exchangeable Al in both substrates. Substantial increase of electrical charge was noticed only in substrate A. Consequently Ca and Mg reloading in substrate B was mainly due to ion exchange with Al, whereas in substrate A the major part of the increase in exchangeable Ca and Mg was due to enhanced organic charge. Kieserite induced very little changes in soil pH and all modifications in the composition of exchange sites were achieved after the passage of the sulfate peak. In the A substrate, the increase of Mg loading resulted from an exchange process with Ca, whereas it was achieved at the expense of exchangeable Al in the B substrate. Calcium and Mg losses from the soil columns after 32 d were greater with kieserite than with dolomite. These losses were also larger for the hemiorganic A substrate than for the mineral B substrate. These results imply that both the charge characteristics of the substrate (variable or fixed) together with the kind of Mg-fertilizer are essential to consider in fertilization programmes.

The effect of soil texture on the dissolution of North Carolina phosphate rock

SUMMARYLaboratory investigations of the dissolution of North Carolina phosphate rock (PR) in soil, as affected by soil texture, were conducted using soils created by mixing various proportions of the &lt;45 μm and &gt;45 μm fractions of a lateritic soil. The dissolution of PR in soil, and the resulting changes in plant available P, were estimated by measuring increases in exchangeable Ca (ΔCa) and NaHCO3‐extractable P (ΔPb), respectively. The total fertilizer phosphate dissolved (ΔP) was calculated from δCa values based on the assumption that dissolution of PR released amounts of Ca and P in a constant ratio determined by the stoichiometry of the PR. δP increased with increasing content of &lt;45 μm particles. APb also increased with the percentage of &lt;45μ fraction, with about 20% of AP being recovered as APb. A smaller proportion of dissolved P was soluble in NaHCO3 for the soil comprising only the &lt;45μ particles. The increase in δP with increased percentage of &lt;45 μn soil was probably due inter alia to the greater P‐sorption, Ca‐sorption and the pH buffering capacity of the fine grained soil constituents.

The effects of moisture regime and incubation period on the dissolution of North Carolina phosphate rock in soil

The effect of soil water content on the dissolution of reactive North Carolina phosphate rock (PR) in a lateritic soil was investigated in a laboratory incubation study. Soil-PR and soil-KH2PO4 mixtures were incubated at different water contents for different periods and dissolution of PR was followed by measuring the increases in exchangeable Ca (�Ca) in the soil. The phosphorus released (�P) was calculated from the composition of the PR. Increases in bicarbonate-soluble P (�Bic P) resulting from PR dissolution were also determined. Changes in both �P and �Bic P can be described by exponential functions of the form �P or �BicP = � - Bexp (-CW), where W is the gravimetric water content of the soil and A, B and C are constants. Little additional dissolution occurred for W &gt; 13% which was about the water content at free-draining field capacity. For an incubation period of 280 days, PR dissolution increased from 4% for air-dry soil to 13% for W = 12.5%, increasing to about 17% for W = 100%. The �Bic P/�P ratio for KH2PO4-fertilized soil was initially much higher than that for PR, but decreased for both sources with period of incubation and values almost converged at 0.20 after 50 days. The effect of wet-dry treatments on AP was also investigated for soil amended to pH values of 3.76 and 5.09. After a 33 day contact period including three 2-day drying periods, there was 40% and 38% of PR dissolved for continuously wet and wet-dry treatments, respectively, at pH 3.76. The corresponding values for pH 5.09 were 22% and 21%. Therefore, these data indicate that a short drying period does not substantially affect PR dissolution (�P) and bicarbonate-soluble P (�Bic P) levels.

The influence of the addition of goethite to soil on the dissolution of North Carolina phosphate rock

This laboratory experiment investigated changes in the dissolution of North Carolina phosphate rock and NaHCO3-soluble P arising from the addition of goethite (�-FeOOH) to soil. Increasing goethite in the soil increased the amount of phosphate rock (PR) dissolution as measured by the increase in exchangeable Ca (�Ca) values. Increased dissolution was, however, associated with decreased NaHCO3- soluble P due to P retention by goethite. The proportion of P dissolved from PR that was soluble in 0.5 M NaHCO3 solution decreased with contact period and with increased goethite. The increase in exchangeable Ca (�Ca) was a better indicator of the extent of PR dissolution in goethite-containing soils than NaHCO3-soluble P.

Soil Fertility Dynamics after Clearing a Tropical Rainforest in Peru

AbstractThis paper describes changes in soil properties during the first 8 y after clearing a fine loamy, siliceous, isohyperthermic Typic Paleudult at Yurimaguas, Peru. Three adjacent fields under a 17‐year old secondary forest were slashed, burned, and planted to three crops per year with or without fertilization for 8 years. Ash from the burn increased soil pH, available N, P, K, Ca, Mg, and decreased exchangeable Al. Six months after burning, however, the levels of available N and K were reduced, along with sporadic S, Cu, and B deficiencies. Topsoil organic C and total N decreased at an annual rate of 25% during the first year but approached an equilibrium afterwards. The rapid organic matter decomposition probably released organic matter‐bound Al which reversed the liming effect of the ash. Phosphorus and Mg became deficient during the second year, Ca within the first 30 months and Zn and Mn during the fourth year. Molybdenum deficiencies occurred sporadically, particularly when locally produced legume seed was used. Soil chemical properties have improved with continuous cultivation because of liming and fertilizer additions. After 8 years and 21 crops, topsoil pH increased to 5.6, exchangeable Ca increased by 10 times, effective CEC doubled, available P increased from 5 to 39 mg kg−1, and Al saturation decreased from 82 to 1%. The 15‐ to 50‐cm layer of the subsoil has undergone significant increases in exchangeable Ca and Mg and a decrease in Al saturation. This should promote deeper root development. The time at which nutrient deficiencies appeared and the amounts of fertilizer or lime needed to correct them varied substantially between the three fields, despite their close proximity, same preclearing vegetation, geomorphic position, and same soil classification at the family level.

Short‐Term Soil Chemical and Crop Yield Responses to Limestone Applications1

AbstractLimestone applications ranging from 0 to 17.92 metric tons/ha were applied to three acid soils for the purpose of measuring soil chemical and crop yield responses to increased levels of soil pH during the initial growing season following limestone application. Corn (Zea mays L.), barley (Hordeum vulgare L.), and alfalfa (Medicago sativa L.) were planted in a Goldsboro sandy loam (Aquic Paleudult), Pacolet sandy clay loam (Typic Hapludult), and Frederick silt loam (Typic Paleudult), respectively. Sixteen weeks after treatment, soil pH and exchangeable Ca and Mg increased, while exchangeable Al decreased with increasing lime rate. Initial crop yields increased with lime applications on all soils. Exchangeable Al saturations of 18, 8, and 11% of the effective CEC decreased corn, barley, and alfalfa yields. Regression analysis indicated that reduction in exchangeable Al was responsible for increases in corn yields (R2=0.59) and that increases in exchangeable Ca along with decreases in exchangeable Al accounted for increased alfalfa yields (R2=0.80).

Comparative Lime Effects on Continuous No‐Tillage and Conventionally Tilled Corn1

AbstractBecause the absence of tillage precludes the mixing of lime with soil when no‐tillage corn (Zea mays L.) is grown, an experiment was conducted to determine if surface application would be effective. Information on the subject is not presently available but is needed to guide growers in neutralizing soil acidity caused by high rates of nitrogen applied to corn.Field studies over an 8‐year period compared continuous no‐tillage corn with surface‐applied lime to continuous conventionally tilled corn with lime incorporated into the soil. Comparisons of the two tillage methods were also made without lime to determine the degree of response to lime. Lime increased corn yield more than twice as much in no‐tillage culture as in conventional tillage. Lime was essential for highest yields with both tillage methods but the yield increase due to surface applied lime in no‐tillage culture averaged 31.3%, compared to a 13.5% yield increase due to incorporated, lime in conventional tillage culture.Associated with the larger yield increase from lime in the no‐tillage culture were 1) a higher pH in the 0 to 10‐cm soil layer (averaging 6.4 in no‐tillage compared to 6.0 in conventional tillage) in the eighth year; and 2) larger increase in exchangeable Ca and a reduction in exchangeable AI in the 0 to 10‐cm layer. The pH and exchangeable Ca and AI in the 10 to 20‐cm soil layers from tilled and nontilled soil were almost identical. A highly significant correlation was found between maturity of the corn and yield increase due to lime. Thus, it appears probable that the principal mechanism for the yield reduction caused by the lack of lime was reduced growth. This was especially apparent in early growth stages but was partially overcome later. It was more noticeable in no‐tillage corn than in conventionally tilled corn. At harvest, the increase in dry matter content of no‐tillage corn ears which was caused by lime was larger than that in conventionally tilled corn.Water use efficiency for the increased corn grain yield due to lime in no‐tillage was calculated to be almost three times that in conventional tillage.

The sodium dependence of embryonic induction

Induction of nerve and pigment cells in presumptive epidermis of the frog gastrula has been found to be dependent upon the concentration of the sodium ion. This sodium dependence is shown by small aggregates of presumptive epidermis cells induced by sucrose or by ions (Li +, Ca 2+, Mg 2+, Mn 2+) to differentiate into nerve or pigment cells. Following these treatments, induction takes place when the external NaCl concentration is 0.088 M, but does not occur at 0.044 M. This range of concentrations is within the physiological range for continuous culture of cell aggregates and explants of amphibian embryos commonly used for studies of induction. Similarly, normal induction of nerve and pigment cells by mesoderm in small explants, prepared from the dorsal lip and lateral marginal zones of the early gastrula, is dependent upon the external concentration of sodium. Nerve and pigment cells are induced by the mesoderm when the culture medium contains 0.088 M NaCl. At 0.044 M NaCl, however, the mesoderm differentiates into muscle and mesenchyme, but induction of nerve and pigment cells does not occur. The sodium dependency of aggregates prepared from early gastrula is restricted to the period of induction. The end of this period corresponds in duration to the end of gastrulation. Cell aggregates prepared directly from presumptive neural plate at the end of gastrulation similarly have become independent of sodium. The sodium dependency of induction in presumptive epidermis cell aggregates by ions is compared to sodium dependency of induction of ectoderm by mesoderm in cell aggregates from early gastrula. The working hypothesis presented is that normal embryonic induction depends upon an endogenous source of ions, and that there is an intracellular release of ions within the embryo during late gastrulation. Preliminary experiments have revealed a threefold increase in exchangeable Ca 2+ within the cells and a forty-fold increase in intracellular Na + during gastrulation. The sodium dependence demonstrated in the present experimental system and postulated for normal embryonic induction is compared to other sodium-dependent systems in transport at tissue, cellular, nuclear, and organelle levels.