Mesic Typic Hapludult Research Articles

Summer Patch Disease Severity on Kentucky Bluegrass in Response to Fertilizer Source

Summer patch is caused by the ectotrophic, root‐infecting fungus Magnaporthe poae Landschoot and Jackson. The disease, which often infects high maintenance turf, can be difficult to control because root infection often occurs six to eight weeks before the appearance of foliar symptoms. Disease severity is reduced when turf is fertilized with ammonium nitrogen (N) sources, compared to nitrate or urea sources of N. Thiosulfate, from (NH4)2S2O3 or K2S2O3, is a nitrification inhibitor which may enhance ammonium uptake of turf by slowing nitrification. N‐SURE is a triazone‐based, slow release N source that is commonly used to fertilize turfgrass. Field studies were conducted from 1995 to 1996 on Kentucky bluegrass (Poa pratensis L.) grown on a Nixon loam (fine‐loamy, mixed, mesic Typic Hapludult) to evaluate the effectiveness of the several N and K sources for their ability to control summer patch disease. Nitrogen fertilizers, N‐SURE, (NH4)2S2O3, and (NH4)2SO4, were applied in combination with either K2SO4 or K2S2O3. The severity of summer patch was greater when the turf was fertilized with N‐SURE in 1995 and 1996 and urea in 1996 compared to (NH4)2S2O3. The N sources, (NH4)2SO4 and (NH4)2S2O3, were strongly acidifying to the upper 10 cm of soil and were very effective in controlling summer patch. The application of K2S2O3 slightly acidified the upper 5 cm of soil but did not suppress the development of summer patch. The ability of thiosulfate to act as a nitrification inhibitor did not appear to play a role in the suppression of summer patch. Since foliar burn may occur if (NH4)2SO4, (NH4)2S2O3, or K2S2O3 are applied to turf without irrigation, the application of water after their use is recommended.

TRANSPORT AND FRACTIONATION OF DISSOLVED ORGANIC MATTER IN SOIL COLUMNS

Dissolved organic matter (DOM) is a heterogeneous mixture of organic compounds that plays an important role in the movement of DOM-associated pollutants. In this study, transport and fractionation of DOM in soils was investigated in flow-through soil columns. Dissolved organic matter derived from spent mushroom substrate weathering was pumped through packed columns (2.5 cm × 10 cm) comprising a coarseloamy subsoil (mixed, semiactive, mesic Typic Hapludult), and effluents were monitored for changes in the composition of DOM. Effluent DOM was characterized for UV absorbance, molecular weight, acidity, and hydrophilicity. Transport through the columns resulted in preferential retention of specific DOM constituents as indicated by comparison with a Br - tracer. During the transport process, effluent DOM exhibited decreasing values of E 2 /E 3 (from 10.3 to 6.2), acidity (from 20.8 to 13.1 mmol c g -1 C), and hydrophilicity (39.0 to 28.4%), and increasing values of molar absorptivity (from 164 to 310 L mol -1 C cm -1 ) and number and weight-averaged molecular weight (from 1770 to 3150 and 2450 to 4180 Da, respectively). These results indicate that DOM fractions with higher molecular weight, higher molar absorptivity, lower E 2 /E 3 ratio, lower acidity, and lower hydrophilicity were adsorbed preferentially by soil minerals, whereas the inverse fractions were transported preferentially. The adsorbed DOM could not be completely desorbed by DOM-free background solution, indicating a strongly bound fraction. Sorptive fractionation of DOM during transport likely affects the transport behavior of DOM-complexed constituents.

Using Soil Phosphorus Profile Data to Assess Phosphorus Leaching Potential in Manured Soils

Transport of P by subsurface flow pathways can be an important mechanism of P transfer from land to water, particularly in manured soils that are artificially drained. This study was conducted to determine whether detailed description and interpretation of soil P profile data provide adequate insight into P leaching potential. Evidence of P translocation within soil profiles of a tile-drained Buchanan (fine-loamy, mixed, semiactive, mesic Aquic Fragiudult)-Hartleton (loamy-skeletal, mixed, active, mesic Typic Hapludults) catena was assessed by measuring oxalate-extractable P, P sorption saturation, Mehlich-3 P, water-extractable P in bulk and clay film samples obtained from individual horizons. Tile-drain monitoring and column leaching experiments were conducted to evaluate interpretations derived from soil P profile data. Soil P fractions were not correlated with P losses in lysimeter studies, indicating the limited potential of using soil profile P data for quantitative prediction of leaching losses. Application of manure to the soil surface resulted in significant increases in leachate P concentrations from the lysimeters. Soil profile P data did, however, provide some evidence of long-term P leaching. While bulk horizon samples did not indicate significant long-term P translocation to soil depths corresponding with artificial drainage, some clay film samples had significantly elevated oxalate P, P sorption saturation and Mehlich-3 P at lower depths. Elevated P concentrations in clay films may be associated with preferential transport of P along soil macropores, although, not all clay films sampled in this study were necessarily associated with active macropores. Thus, soil P profile data appear to provide limited insight into P leaching potential.

Using Soil Phosphorus Profile Data to Assess Phosphorus Leaching Potential in Manured Soils

Transport of P by subsurface flow pathways can be an important mechanism of P transfer from land to water, particularly in manured soils that are artificially drained. This study was conducted to determine whether detailed description and interpretation of soil P profile data provide adequate insight into P leaching potential. Evidence of P translocation within soil profiles of a tile‐drained Buchanan (fine‐loamy, mixed, semiactive, mesic Aquic Fragiudult)‐Hartleton (loamy‐skeletal, mixed, active, mesic Typic Hapludults) catena was assessed by measuring oxalate‐extractable P, P sorption saturation, Mehlich‐3 P, water‐extractable P in bulk and clay film samples obtained from individual horizons. Tile‐drain monitoring and column leaching experiments were conducted to evaluate interpretations derived from soil P profile data. Soil P fractions were not correlated with P losses in lysimeter studies, indicating the limited potential of using soil profile P data for quantitative prediction of leaching losses. Application of manure to the soil surface resulted in significant increases in leachate P concentrations from the lysimeters. Soil profile P data did, however, provide some evidence of long‐term P leaching. While bulk horizon samples did not indicate significant long‐term P translocation to soil depths corresponding with artificial drainage, some clay film samples had significantly elevated oxalate P, P sorption saturation and Mehlich‐3 P at lower depths. Elevated P concentrations in clay films may be associated with preferential transport of P along soil macropores, although, not all clay films sampled in this study were necessarily associated with active macropores. Thus, soil P profile data appear to provide limited insight into P leaching potential.

Morphological Development of Alfalfa Cultivars Selected for Higher Quality

Alfalfa (Medicago sativa L.) maturity at the time of harvest greatly influences forage quality. The objective of this research was to determine if observed quality differences between high quality and other alfalfa cultivars were due to differences in morphological development. Two high‐quality cultivars (‘WL 252HQ’, ‘WL 322HQ’) and two check cultivars (‘5262’, ‘5454’) with similar fall dormancy ratings were established on a Murrill silt loam (fine‐loamy, mixed, mesic Typic Hapludult) in the spring of 1996. During 1997, 1998, and 1999, each cultivar was hand‐sampled weekly for 4 consecutive wk during the spring growth period and for 3 consecutive wk during the three subsequent growth periods. Morphological development and forage quality were determined for each alfalfa cultivar at each sampling. There were no interactions between growth period or sampling times and alfalfa cultivars for either alfalfa maturity or forage quality. Morphological development of the cultivars was not different at any of the sampling times. Averaged across all growth periods and sampling times, crude protein (CP) concentrations and in vitro dry matter digestibility (IVDMD) were 14 and 13 g kg−1, respectively, higher for the high‐quality cultivars (ADF) and neutral‐detergent fiber (NDF) concentrations were 16 and 15 g kg−1, respectively, lower. The data from this research indicates that the difference in quality between the high quality and traditional alfalfa cultivars is not due to differences in morphological development. Selecting for higher‐quality alfalfa was successful and is not an artifact of inadvertently selecting for delayed development.

Growth Responses and Performance of Kentucky Bluegrass under Summer Stress

Cultivars and selections of Kentucky bluegrass (Poa pratensis L.) exhibit varying degrees of summer stress tolerance. Understanding the factors associated with performance under summer stress is important for identifying stress tolerant germplasm. The objective of this field study was to evaluate shoot and root growth responses of 10 Kentucky bluegrass genotypes subjected to high temperature and drought stress conditions in New Jersey. Turf canopy characteristics, shoot and root growth responses, and soil water depletion patterns were evaluated on a Nixon Loam (fine-loamy, mixed mesic Typic Hapludult) and used to characterize Kentucky bluegrass selections having variable summer stress tolerance. Tolerant entries maintained 19% more roots at the 15- to 30-cm depth in 1995 and 65% more roots at the 30- to 45-cm depth than intolerant entries. Gravimetric soil water contents of tolerant plots were significantly lower at the 15- to 30-cm depth than intolerant entries for both years. Tolerant Kentucky bluegrass, able to exploit deep soil moisture under heat and drought conditions, exhibited significantly fewer summer stress symptoms, had significantly lower stomatal resistance (based on subset of cultivars), and maintained canopy temperature 5°C cooler than intolerant entries at the end of stress periods. This indicated that maintenance of transpirational cooling was an important factor associated with better summer stress performance of turf plots under high temperature and drought conditions in New Jersey.

Neotyphodium coenophialum‐endophyte infection affects the ability of tall fescue to use sparingly available phosphorus

Neotyphodium coenophialum, (Morgan‐Jones & Gams) Glenn, Bacon & Hanlin, infected tall fescue (Festuca arundinacea Schreb.) plants perform better than non‐infected isolines on phosphorus (P)‐deficient soils. Our objective was to characterize growth and P uptake dynamics of tall fescue in response to endophyte infection and P source at low P availability in soil. Two tall fescue genotypes (DN2 and DN4) infected with their naturally occurring N. coenophialum strains (E+), and in noninfected (E‐) forms were grown in Lily soil (fine loamy siliceous, mesic Typic Hapludult) in a greenhouse for 20 weeks. Three soil P treatments were imposed: no P supplied (control) and P supplied as commercial fertilizer (PF) or as phosphate rock (PR) at the level of 25 mg P kg‐1 soil. Interaction of tall fescue genotype and endophyte status had a significant influence on mineral element uptake suggesting high specificity of endophyte‐tall fescue associations. Endophyte infection did not affect root dry matter (DM) when no P was supplied but shoot DM was reduced by 20%. More biomass was produced and greater P uptake rate occurred in PR than PF treatment. Root DM was greater in E+ DN4 than E‐DN4 when supplied with either PF or PR. In contrast, endophyte infection did not affect root DM of DN2, regardless of P source. Relative growth rate (RGR) of E+ plants grown with PR was 16% greater than that of E‐plants. Endophyte infection did not improve growth or P uptake in PF treatment. When PR was supplied, P uptake rate was 24% greater in E+ DN2 than E‐ DN2, but endophyte infection did not benefit DN4. Phosphorus‐use efficiency was 6% less in E+ DN2 but 16% greater in E+ DN4 compared to E‐ plants, regardless of P source. Root exudates of E+ DN2, but not E+ DN4 solubilized more P from PR than those of E‐ plants. The correlation between root RGR and P uptake rate was relatively high for E‐ plants (r=0.76), but low for E+ plants (r=0.27) grown with PR. Results suggest that P uptake by E+ tall fescue might rely on mechanisms other than an increase in root biomass (surface area). Endophyte infection modified tall fescue responses to P source. This phenomenon was associated with modes of P acquisition which included enhanced activity of root exudates in releasing P from PR in E+ plants (DN2), and increased root biomass (DN4). The dominant means of P acquisition may be determined by a specific association of endophyte and tall fescue genomes. Endophyte‐tall fescue association plasticity contributes to widespread success of symbiotic in marginal resource conditions.

Rainfall influence on imazethapyr bioactivity in New Jersey soils

Greenhouse studies were conducted with soil columns to determine the influence of rainfall amount, intensity, and time of application on the bioactivity of 0.07 kg ae ha−1imazethapyr in three soils of New Jersey: the Berryland sand (BLS) (sandy, siliceous, mesic Typic Haplaquod), Aura sandy loam (ASL) (mixed, mesic Typic Hapludult), and Quakertown silt loam (QSIL) (mixed, mesic Typic Hapludult). The Brockman-Duke simulated rainfall machine was used for rainfall application and smooth pigweed as an imazethapyr bioactivity indicator. As rainfall amount increased from low to high (75 to 300 mm mo−1equivalent) imazethapyr bioactivity declined significantly in BLS and ASL but was unaffected in QSIL. Rainfall intensity from 6 to 25 mm h−1had no effect on imazethapyr bioactivity in the three soils. A delay in rainfall application up to 14 d after herbicide application significantly reduced the bioactivity of imazethapyr in BLS but had no effect in ASL and QSIL.

Soil‐Climate Effects on Nitrate Leaching from Cattle Excreta

AbstractManagement intensive grazing (MIG) is a grazing system in which animals at a high stocking density are rotated through several paddocks at short time intervals (12–24 h) so that animal performance is maximized. Although MIG has the potential to increase dairy farm profitability in the northeast USA, recent work in this region has shown that a substantial amount of N recycled through urine is leached below the root zone. How soil properties, particularly water‐holding capacity, can affect NO3‐N leaching from beneath urine and feces spots under the climatic conditions of the northeast USA is not known. We conducted a field study to measure NO3‐N leaching loss from spring‐, summer‐, and fall‐applied urine and summer applied feces beneath N‐fertilized orchardgrass (Dactyls glomerata L., cv. Pennlate) using large drainage lysimeters installed in two soils that differed greatly in soil water storage capacity. The study sites were located in central Pennsylvania on a Hagerstown silt loam soil (fine, mixed, mesic Typic Hapludalf) and a Hartleton channery silt loam (loamy‐skeletal, mixed, mesic Typic Hapludult). Compared to the Hagerstown soil, the Hartleton soil provided an 85% decrease in plant N uptake, a 52% increase in leachate volume, but no significant increase in NO3‐N leaching beneath urine spots. However, the lower soil water‐holding capacity of the Hartleton soil caused the NO3‐N leaching losses to be more evenly distributed over the year.

Runoff and Sediment Losses from Natural and Man‐Made Erosion Control Materials

Man‐made erosion control materials are increasingly being used at construction sites. The performance of these materials in comparison to natural materials is largely unknown. A rainfall simulation study was designed in which four man‐made materials (wood excelsior, jute fabric, coconut fiber blanket, and coconut strand mat) and two natural materials (straw and turfgrass sod) were evaluated. The erosion control materials were evaluated on a Sassafras loamy sand (fine loamy, mixed mesic Typic Hapludult) having a 8% slope and on a Sassafras sandy clay loam (fine, silty, mixed mesic Typic Hapludult) having a 14 to 21% slope. Disturbed soil surface areas (0.76 m2 each) were covered with each material and subjected to a 96 mm hr−1 simulated rainstorm. Runoff and sediment loss rates were determined every 5 rain for 35 min after recording the time required for runoff initiation. Sod was the only material that extended the time required for runoff initiation. Runoff from all materials was less than bare soil for the first 5 rain of runoff; however, only straw, jute, and sod reduced runoff over the entire storm event. The total amount of runoff, compared with bare soil, was decreased by 61% for sod, 25% for straw, and 16% for jute. Erosion control materials reduced bare soil erosion by 80 to 99%. Of the man‐made rosion control materials, only jute reduced runoff and sediment losses at both locations. Therefore, of the materials tested, only sod, straw, and jute would be expected to effectively reduce both runoff and sediment losses

Harvest Management Effects on Dry Matter Yield, Forage Quality, and Economic Return of Four Cool-Season Grasses

Perennial cool-season grasses are widely grown in Pennsylvania and the northeast USA for forage. Harvest management practices that maximize annual economic return of these grasses have not been adequately identified. The objectives of this research were to determine tbe effect of harvest number on dry matter (DM) yield, forage quality, and economic return of orchardgrass (Dactylis glomerata L.), reed canarygrass (Phalaris arundinacea L), smooth bromegrass (Bromus inermis Leyss.), and timothy (Phleum pratense L.). Established stands of these grasses on a Murrill silt loam (fine-loamy, mixed, mesic Typic Hapludult) were harvested at intervals of 70, 45, and 35 d (two, three, or four harvests per year, respectively) during four consecutive years. In all years and for all grass species, forage quality (crude protein [CP] and digestible dry matter [DDM]) was greatest when the forage was harvested at a 35-d interval. However, in years when rainfall was below normal, the 35-d harvest interval resulted in the lowest DM yields. There was no difference in net economic return for any species when rainfall was below normal. In years when rainfall was at or above normal, the 35 and 45-d harvest interval produced greater net economic return than the 70-d interval for all grasses except timothy, which did not differ in economic return among harvest schedules. The highest quality forage and greatest net economic return were obtained in years with normal or greater rainfall when orchardgrass, reed canarygrass, and smooth bromegrass were harvested at intervals of 35 to 45 d. Harvest intervals for the same species in dry years and timothy in either dry or wet years should be based on the nutrient needs of the consuming animal. Forage for high producing animals (e.g., lactating dairy cows), which require relatively high forage digestibility to achieve adequate intake levels, must be harvested more frequently (35 to 45 d) than forage for animals with lower intake requirements (e.g., nonlactating cows).

Phosphorus Nutrition Affects Wheat Response to Water Deficit

AbstractPlant leaf area affects both plant growth and yield. Although the effects of phosphorus and water availability on leaf area development have been studied as isolated factors, little work has been done on their possible interactions. A pot experiment was conducted to investigate the effects of both P and water availability on early leaf appearance and expansion in soft red winter wheat (Triticum aestivum L.), and to determine whether the effect of water deficit changes at each level of P nutrition and whether the soil water content affects plant P uptake. The soil was a Lonewood loam (fine‐loamy, siliceous, mesic Typic Hapludult), which had an available P level of 8.2 mg P kg−1 (Mehlich III). Additional P was applied at 0, 10 and 20 mg P kg−1 soil. Water treatments consisted of keeping soil‐water content at 80% (well watered) and 53% (stressed) of the 10 kPa soil‐water content. Plant development, leaf appearance and expansion, and stomatal resistance were measured during the experiment. At harvest (38 d after emergence), leaf area, aboveground biomass, and P concentration were measured. Phosphorus and water availability exhibited a significant interaction on tiller and leaf appearance, which were reduced by water stress but only at 0 applied P. As individual factors, P and water influenced different plant features. Lack of applied P decreased the rate of leaf appearance and, therefore, the final number of leaves and leaf area per plant. Water deficit reduced individual leaf area and, at 0 applied P, reduced rate of leaf appearance, number of simultaneously expanding leaves, and final number of leaves. Phosphorus uptake was increased only with added soil P, and not by water stress. The ability of plants to cope with mild water stress was enhanced by adequate P nutrition.

Loessial Soils of Delaware: Taxonomy and Map‐Unit Assessment

AbstractMap units named for the Matapeake series (fine‐silty, mixed, mesic Typic Hapludults) comprise one‐third of the Coastal Plain in the soil survey of northern Delaware. The concept was one of well‐drained soils formed in thin loess over coarse‐textured fluvial sediments. This study uses characterization data from pedons within the loess‐blanketed terrain of northern Delaware to assess the taxonomy and composition of Matapeake map units. All pedons are Alfisols rather than Ultisols, and this status has not been influenced by liming. Fine‐loamy rather than fine‐silty soils typically occur where loess is <80 cm thick. Much soil variability exists on interfluves where thin loess discontinuously blankets the irregular surface of the sandy Pensauken Formation. This results in an inability to map specific consociations, even for large‐scale, detailed surveys. The existing soil survey used specific map units — consociations named for phases of soil series — that do not adequately depict the diversity on mappable landscapes. The Matapeake and associated series used in this area are too narrowly defined in ranges of characteristics, are too general in geographic setting, have loess thickness limits that are not concordant with particle‐size classes, and leave gaps in the lithologic‐hydrologic continuum. They therefore provide little utility for organizing knowledge, understanding relationships, or as objects for research. Soil survey in this area requires more generalized map units, greater emphasis on stratigraphy and geomorphology and their interaction to influence hydrology and lithology, and less emphasis on artificial conceptual groupings at the lowest taxonomic category, the series.

Soil and minespoil fill as media for renovation of nitrogen and phosphorus in domestic wastewater

Development of Appalachian coal mining regions of the USA has been severely hampered by lack of domestic waste disposal technologies suited to fills. The suitability of on-site wastewater treatment and disposal systems (OSWTDS) in fill material is uncertain due to the effects of surface mining on soil physical properties. This research was conducted to evaluate the potential for renovation of N and P present in domestic wastewater by fills produced from mining operations. Nitrogen and P were chosen because of their potential adverse environmental impacts. Soil-fill (a mixture of Jefferson, fine-loamy, siliceous, mesic Typic Hapludult and Muskingom, fine-loamy, mixed, mesic Typic Dystrochrept soils) and minespoil (spoil)-fill (blasted rock material associated with the Taggart Marker and Low Splint Bench coal seams of the Upper Middle Wise Formation) were used in this study. Septic tank effluent (STE) and sand filter effluent (SFE) were applied to spoil-fill columns at four loading rates (0, 5.4, 10.8, and 21.6 L m-2d-1) and spoil-fill columns at one loading rate (21.6 L m-2d-1) for a period of 20 wk. Renovation of wastewater was assessed by determining the concentration of N and P present in column leachate. Reduction of inorganic N (NO3- + NH4+), based on N/Cl ratios, ranged from 14.9 to 32.1% after the varying application rates of STE and SFE passed through the soil columns. However, leachate NO3--N concentrations were still above the 10 mg-1 drinking water standard. The quantity of P emerging from the spoil-fill columns (3.0 mg P L-1) was higher than anticipated and may be related to the indigenous P present in the minespoil. Sorption of P in the soil-fill column decreased with increased STE and SFE application (reductions ranged from 99.1 to 74.4%). Results from this study indicate that there is potential for renovating wastewater in OSWTDS in selected soil-fill areas in reclaimed minelands.

Residue Height Influences Stand Dynamics of Alfalfa Grown on a Shallow Soil

AbstractMultiuse alfalfa (Medicago sativa L.) cultivars have been developed to meet the need for high‐quality and productive forages. A continuum of residual tissue quantities can occur in a stand because of management factors or livestock selectivity, depending on the production system. We conducted a field study to determine the influence of residual herbage height on the productivity and persistence of alfalfa under natural rainfall on a shallow, acidic soil (Lily series; fine‐loamy, siliceous, mesic Typic Hapludults) typical of those found throughout the Appalachian Plateau. Three replicates of ‘Alfagraze’, ‘Apollo’, and ‘Cimarron’ alfalfa in each block of a randomized complete block design were clipped to residue heights of <2, 5, or 10 cm. Averaged over the experiment, Apollo yield was greatest, at 8.7 Mg ha−1; Alfagraze (8.0) and Cimarron (7.9) yields were about 10% less than Apollo. Clipping to 10 cm produced yields that were as much as 38% less than with shorter heights. Crown density decreased from about 400 to about 80 crowns m−2 during the experiment. Clipping to <2 cm caused the greatest variation in crown density among cultivars, with Alfagraze having the most and Cimarron the fewest crowns. With a 10‐cm residue, weed competition increased and plant size and shoot number were depressed, especially in Alfagraze. Plants with large crowns produced more stems, which compensated for the gradual decline in plant population. The loss of larger‐crowned plants during 1994 to 1995 was reflected in fewer shoots and reduced yield, and created a situation where increased productivity per plant could no longer compensate for plant losses. Reestablishment recommendations based on shoot numbers should be determined after the first clip in the growing season, and not in spring (when shoot numbers are changing rapidly). Our findings suggest that acceptable alfalfa yields can be obtained on a shallow acidic soil with surface liming, fertilizer input, and close clipping. The range of residue heights likely to occur in a stand of alfalfa influence productivity and persistence. Allowing a 10‐cm residue to remain would probably accelerate plant loss and yield reduction from the stand.

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.

Kinetics of Phosphate Rock Dissolution in Acidic Soil Amended with Liming Materials and Cellulose

AbstractPhosphate rock (PR), coal combustion by‐product (CCBP), limestone, and organic materials are promising amendments for low P, acid soils, and two or more of the amendments are commonly applied to improve crop yields in acid soil. However, the interactions between these amendments in acid soil are not fully understood. The effects of CCBP, limestone, and cellulose application on dissolution of North Carolina phosphate rock (NCPR) in an acid Lily loam (fine‐loamy, siliceous, mesicTypic Hapludult) from West Virginia were examined in an incubation study. Based on the ΔP‐NaOH estimation method, ≈ 30% of the added NCPR was dissolved after 60 d of incubation. The NCPR dissolution decreased drastically with increasing rate of CCBP, particularly when it was applied together with limestone, whereas cellulose addition tended to enhance NCPR dissolution. Dissolution of NCPR was well described by first‐order, Elovich, and Langmuir kinetic equations. The average r2 values between the experimental data of NCPR dissolution and the three models were 0.829*, 0.851**, and 0.930**, respectively, for 17 soil samples with and without amendments. Half‐life (t1/2) from the first‐order reaction could be employed as a simple measure of the NCPR dissolution rate. Constants A and b derived from the Elovich equation were related to the initial and average dissolution rate of NCPR. The potential maximum dissolution of PR from the Langmuir equation provided an estimate of the dissolution extent of NCPR. All four kinetic parameters, particularly t1/2 and A, were closely correlated with CCBP application rates. These parameters appeared useful in evaluating the effects of CCBP application on NCPR dissolution in the acid soil and might also be applicable to predicting PR dissolution for a wide range of soils with different properties.

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.

Soil Organic Matter Mineralization after Compost Amendment

AbstractThe addition of composts and manures to soils has often resulted in increased plant yields that are not obviously related to the nutrients in the added organic material. A study was conducted to determine if compost additions to soil resulted in increased mineralization of soil organic matter (SOM). The organic matter of a Sassafras sandy loam soil (fine‐loamy, siliceous, mesic Typic Hapludult) was labeled with 14C by incubating uniformly labeled wheat (Triticum aestivum L.) straw with the soil through a minimum of 60 wetting‐drying cycles during 2 yr. A municipal solid waste‐biosolids compost (MSWC) or a biosolids compost (BC) was added to the labeled soil or to acid‐washed sand and incubated for 1440 h. Decomposition of MSWC was low with 95% of the compost‐C remaining in sand or soil after 1440 h. Ninety‐two percent of BC‐C remained in sand and 86% remained in soil after 1440 h. Total and 14CO2 data indicated that neither compost stimulated SOM decomposition. Municipal solid waste‐biosolids compost reduced slightly SOM decomposition at 545 and 715 h. The soil, however, stimulated BC decomposition. Nitrogen mineralization of the BC + soil mixture was greater than soil alone, and the N apparently came from the compost. The benefits from addition of BC to Sassafras soil was not attributed to increased mineralization of SOM.

Kinetics of Phosphate Rock Dissolution in Acidic Soil Amended with Liming Materials and Cellulose

AbstractPhosphate rock (PR), coal combustion by‐product (CCBP), lime‐stone, and organic materials are promising amendments for low P, acid soils, and two or more of the amendments are commonly applied to improve crop yields in acid soil. However, the interactions between these amendments in acid soil are not fully understood. The effects of CCBP, limestone, and cellulose application on dissolution of North Carolina phosphate rock (NCPR) in an acid Lily loam (fine‐loamy, siliceous, mesicTypic Hapludult) from West Virginia were examined in an incubation study. Based on the ΔP‐NaOH estimation method, ≈ 30% of the added NCPR was dissolved after 60 d of incubation. The NCPR dissolution decreased drastically with increasing rate of CCBP, particularly when it was applied together with limestone, whereas cellulose addition tended to enhance NCPR dissolution. Dissolution of NCPR was well described by first‐order, Elovich, and Langmuir kinetic equations. The average r2 values between the experimental data of NCPR dissolution and the three models were 0.829*, 0.851**, and 0.930**, respectively, for 17 soil samples with and without amendments. Half‐life (t1/2) from the first‐order reaction could be employed as a simple measure of the NCPR dissolution rate. Constants A and b derived from the Elovich equation were related to the initial and average dissolution rate of NCPR. The potential maximum dissolution of PR from the Langmuir equation provided an estimate of the dissolution extent of NCPR. All four kinetic parameters, particularly t1/2 and A, were closely correlated with CCBP application rates. These parameters appeared useful in evaluating the effects of CCBP application on NCPR dissolution in the acid soil and might also be applicable to predicting PR dissolution for a wide range of soils with different properties.