K. D. Ritchey

Influence of soil solution aluminum on root elongation of wheat seedlings

Wheat (Triticum aestivum L.) seedlings were grown for 4 days in an acid soil horizon treated with 10 levels each of Ca(OH)2, CaSO4 and CaCl2. The treatments resulted in a wide range of Al levels and Al speciation in soil solution. Seedling root length in the Ca(OH)2 treatments was significantly related (p<0.01) to calculated Al3+ activity in soil solution. The Al−SO4 complex in soil solution had a negligible effect on the root growth of Hart wheat, thus confirming the previously reached conclusion concerning the nonphytotoxicity of Al−SO4. The short-term seedling root growth technique used in this investigation allowed for separation of Al effects on root elongation from those on plant nutrition and should be useful for studying Al toxicity relationships in soil.

Calcium sulfate or coal combustion by-product spread on the soil surface to reduce evaporation, mitigate subsoil acidity and improve plant growth

Removal of sulfur dioxide from flue gas produced by coal-burning power plants has increased the availability of by-products that may be useful as soil amendments for agriculture. We studied the effects of surface layers (caps) of fluidized bed combustion residue-fly ash mixture (FBCR-FA) or calcium sulfate on reduction of evaporative water losses and improvements in subsurface acid soil chemical characteristics. Caps 3.8 cm thick of porous FBCR-FA, hydrated commercial calcium sulfate (CCS), or soil (check) were placed on columns of coarse-loamy, mixed, mesic Umbric Dystrochrept soil of pH 4.2. After the addition of 40 cm of water during a 16-week period, mean daily water loss from the column with the FBCR-FA cap was 0.51 mm compared to 0.98 mm in the check. Mean increase in soil exchangeable Ca in the 5- to 40-cm depth for the CCS treatment was 0.83 cmolc kg−1 and mean pH (H2O) increase was 0.21 units. Mean KCl-extractable Al decreased from 6.08 to 5.52 cmolc kg−1. Roots of sudangrass (Sorghum bicolor (L.) Moench) planted in the columns after removal of the caps reached 2 cm depth in the control, 18 cm in the FBCR-FA and 38 cm in the CCS treated columns after 47 days of growth. The gypsum cap was effective in improving deep rooting in acid soils and the FBCR-FA cap reduced evaporative water losses.

Effect of byproduct, nitrogen fertilizer, and zeolite on phosphate rock dissolution and extractable phosphorus in acid soil

Coal combustion by products (BP) and phosphate rock (PR) have been widely used as cost-effective amendments for acid soils. Information is needed on the proper combination of BP with chemical fertilizers or other organic and inorganic amendments to improve the productivity of acid soils. Chemical analysis and soil incubation studies were carried out to examine the effect of BP, N fertilizers, and zeolite on dissolution of PR and on the status of extractable P in acid soil. Several kinetic models were compared for describing PR dissolution in acid soils that received different amounts of BP, different forms of N fertilizer, and zeolite. PR dissolution in acid soil measured by 0.5 M NaOH extraction was best described by a Langmuir kinetic model (r2=0.988**, followed by an Elovich (r2=0.950**), a two-constant rate (r2=0.947**), a parabolic diffusion (r2=0.905**), and a first-order reaction equation (r2=0.637*). A second-order reaction equation was the poorest among various models tested (r2=0.484). Addition of BP, N fertilizers, and zeolite to the PR-amended soil did not affect the good fitness of PR dissolution to these kinetic equations. Increasing BP addition decreased initial and average dissolution rate and potential maximum dissolution of PR during the incubation period of 132 days as calculated from the Elovich and Langmuir kinetic models. In general, NH4NO3 and (NH4)2SO4 increased the initial rate and decreased slightly the average PR dissolution rate due to a rapid but short-term acidifying effect. On the other hand, urea and zeolite decreased the initial rate of PR dissolution due to higher pH and increased the average PR dissolution rate because of long and persistent acidification by urea and slow but continued removal of Ca by zeolite. The effect of N fertilizers and zeolite on the potential maximum dissolution of PR was related to amounts of BP added. Extractable P in the PR-amended soils as determined by 0.5 M NaHCO3 was closely correlated with P released by PR dissolution. The ratio of increased NaHCO3-extractable P due to PR application divided by the total amount of P released from PR dissolution measured by NaOH extraction might reflect relative availability of P from PR dissolution. This ratio was increased by addition of BP, urea, and zeolite but decreased by NH4NO3 and (NH4)2SO4.

Effect of phosphate rock, coal combustion by-product, lime, and cellulose on ryegrass in an acidic soil

Remediation of soil acidity is crucial for increasing crop production and improving environmental quality of acid infertile soils. Soil incubation and greenhouse pot experiments were carried out to examine the interactions between phosphate rock (PR), coal combustion by-product (BP), dolomitic lime (L), and cellulose (C) in an acidic soil and their effects on ryegrass (Lolium perenne L. cv ‘Linn’) growth. BP and PR application increased plant P content and dry matter yield (DMY) of shoots and roots by improving soil Ca availability and reducing Al toxicity. Application of BP at low rates (5 to 10 g BP kg-1) with PR appeared to decrease both plant P content and DMY compared to PR application alone. The reduced DMY is due to an increased Al concentration in soil solution as a result of displacement of sorbed Al by Ca of BP. Increases in DMY were obtained by addition of lime along with PR and BP at low rates or by increasing BP application rates above 15 g kg-1. This improved plant response was likely related to alleviation of Al toxicity by CaCO3 contained in the BP. In addition to raising the pH to an acceptable level for plant growth, the dolomitic lime supplied needed Mg for plants, thereby maintaining a good balance between available Ca and Mg for plants in the BP- and PR-amended soils. The addition of cellulose to the BP- and PR-amended soils reduced water-soluble Al and increased DMY. Plant growth increased PR dissolution by 2.4 to 243% in a soil with low available P. Use of BP at moderate rates with PR and dolomitic lime appears to be the best combination in increasing crop yields on infertile acidic soils.

Effect of phosphate rock, lime and cellulose on soil microbial biomass in acidic forest soil and its significance in carbon cycling

Abstract Phosphate rock (PR), limestone, coal combustion by-product (CCBP) high in Ca and high organic manures are potential amendments for increasing agricultural production in the acidic soils of the Appalachian region. The objective of this study was to examine effects of PR, CCBP and cellulose addition on soil microbial biomass in an acidic soil based on the measurement of soil microbial biomass P (Pmic) and on the mineralization of organic matter. Application of PR alone or in combination with CCBP increased Pmic. The Pmic was far less when the soil received PR in combination with limestone than with PR application alone or PR in combination with CCBP. Either CCBP or limestone application alone considerably decreased Pmic in the soil due to reduced P solubility. Cellulose addition alone did not increase Pmic, but Pmic was significantly increased when the soil was amended with cellulose in combination with PR. The decomposition of added cellulose was very slow in the soil without PR amendment. However, mineralization of both native organic matter and added cellulose was enhanced by PR application. Mineralization of organic matter was less when the soil was amended with PR in combination with high rates of CCBP (> 2.5%) because PR dissolution varied inversely with amount of CCBP addition. Overall, CCBP had no detrimental effect on soil microbial biomass at low application rates, although, like limestone, CCBP at a high rate may decrease Pmic in P-deficient soils through its influence on increased soil pH and decreased P bioavailability in the soil. Application of PR to an acidic soil considerably enhanced the microbial activity, thereby promoting the cycling of carbon and other nutrients.

Flue gas desulfurization gypsum improves orchardgrass root density and water extraction in an acid subsoil

In Appalachia, many soils are acidic, high in exchangeable aluminium, and low in calcium. Large amounts of high gypsum flue gas desulfurization (FGD) by-products are currently disposed of into landfills, although they have potential value as a soil amendment for the region. This study was conducted to determine if leaching an acid subsoil with a saturated solution of a FGD by-product can improve the subsoil as a rooting media for orchardgrass (Dactylis glomerata L.) which is widely used for pasture in the region. Orchardgrass was grown in soil from a pHc 3.8 (in 0.01 M CaCl2) Lily loam Bt horizon (fine loamy siliceous, mesic, Typic Hapludult) leached with two different rates of a saturated FGD by-product aqueous solution, as well as in soil that was limed, and an unamended soil. Water use by a clipped and partially enclosed vegetative canopy was measured in a growth chamber during two drying cycles. Small but consistent increases in water use were correlated with decreases in aluminium saturation of the soil. The effect was greatest during the second drying cycle. Increases in root biomass were also correlated with decreases in aluminium saturation. The effect of treatment on the pattern of water use altered after the first drying cycle when water uptake became most restricted in the unamended treatment. The manganese content of leaf tissue increased from 208 mg kg-1 to 570 mg kg-1 between the unaltered and highest leaching rate treatment. The highest level was still below the 2000 mg kg-1 that is considered toxic to grazing animals. These results suggest that the application of high gypsum FGD by-products to pastures in Appalachia has the potential to improve root growth and functioning in subsoil horizons, but some care may be needed to monitor forage quality.

Chemical properties of acid soil treated with coal combustion by‐products and leached

Abstract Application of coal combustion by‐products (CCBs) to acid soils can have beneficial or detrimental effects. A column study was conducted to determine the effects of CCBs on mitigating acid soil properties after leaching with 138 cm deionized water. Columns containing 105 cm acidic Lily soil (Typic Hapludult) had mixed in the top 15 cm the following treatments (g/kg soil): no CCB or limestone (check); dolomitic limestone (lime) at 3.98; high‐calcium sulfate (CaSO4) flue gas desulfurization (FGD) by‐product (BP) at 15.88; combination of lime+FGD at rates given; high‐CaSO4 FGD BP enriched with Mg (FGD+Mg) at 15.88; and fluidized bed combustion (FBC) BP at 6.45. After being leached for 39 days, the columns of acid soil treated with high‐CaSO4 by‐products showed higher subsurface pH, calcium (Ca), and sulfur (S) and lower aluminum (AI) and manganese (Mn). In contrast, the lime alone treatment had little effect on subsurface soil properties. Use of dolomitic limestone to supply magnesium (Mg) in conjun...

Soil acidity effects on wheat seedling root growth

Abstract Soft red winter wheat (Triticum aestivum L. cv Hart) was used as a test crop in a bioassay technique to assess acid soil chemical constraints in major hill land soils of the Appalachian Region. Seedling root growth was related to amounts and forms of Al in soil solution and Al extracted by 0.01M CaCl2, 1M KC1, 0.5M CuCl2, and 0.33M LaCl3. Aluminum determined in the various extractants, total soil solution Al and soil solution Al reacting with 8‐hydroxy‐quinoline, pyrocatechol violet, and aluminon showed large differences in root growth prediction ability. In general, Al extracted by 0.01M CaCl2 was a good predictor of root growth. Root elongation was more inhibited in subsurface horizons than in surface horizons. Although surface horizons had the lowest mean pH, the presence of high levels of exchangeable cations tended to ameliorate the Al toxicity. The root bioassay technique adapted here should be useful in assessing the potential Al toxicity of diverse soil types.

Soil and soil solution property effects on root growth of aluminium tolerant and intolerant wheat cultivars

Plant roots are known to exhibit varying degrees of response to the chemical constraints often found in acid soils. Reliable test methods are lacking to assess the extent to which chemical constraints of acid soils limit root growth. The objective of this study was to evaluate the influence of soil and soil solution properties in 55 surface and subsurface horizons of 14 major hill land soils of the Appalachian Region on wheat (Triticum aestivum L.) seedling root growth of Al tolerant (cv. Yecorra Rojo), and intolerant (cv. Wampum) cultivars. The average longest root length (ALRL) of both cultivars was limited in B horizons relative to A and E horizons, suggesting that subsoil rooting in these soils would be restricted. The ALRL of both cultivars was negatively correlated with soil and soil solution Al parameters and was positively related to pH and Ca parameters. Stepwise regression equations were useful in predicting ALRL of wheat seedlings from the soil and soil solution chemical properties of different horizons. Aluminium tolerant and intolerant cultivars used in the study responded differently to the various chemical constraints of acid soils, indicating the existence of intraspecific genetic diversity in wheat cultivars. The root bioassay technique adapted here has great potential for assessing chemical constraints to root growth in diverse acid soils.

Relationship of ryegrass growth to extractable phosphorus in acidic soil amended with phosphate rock, coal combustion by‐product, limestone, and cellulose

Abstract An improved management of phosphorus (P) is crucial for increasing crop production and improving environmental quality of acid infertile soils. Laboratory analyses and greenhouse experiments were conducted to evaluate effects of phosphate rock (PR), coal combustion by‐product (BP), limestone, and cellulose application on the relationship between soil test P and crop growth in acidic soil. Application of PR, BP, limestone, and cellulose increased soil pH, exchangeable calcium (Ca) and magnesium (Mg), and extractable P, and decreased free aluminum (Al) ion in the acid soil. Addition of BP or limestone increased P availability efficiency [PAE, mg dry matter yield (DMY) of plant per mg soil extractable P by Olsen‐P procedure] and P utilization efficiency (PUE, mg DMY of plant per mg P in the plant). There was significant positive correlation between the PAE and BP rates applied alone (r2=O.979, p<0.01) or with either PR (r2=0.972, p<0.01) or PR plus cellulose (r2=0.985, p<0.01). The PUE of ryegrass w...