Phosphorus availability to corn from wood ash-amended soils

Wood ash is a residual material produced during biomass burning. In the northeastern United States up to 80 % of the ash is spread on agricultural lands as a liming amendment with the remainder being disposed of in landfills. As well as raising soil pH, wood ash also adds plant nutrients to soil. This study is an examination of the plant availability of the P in 8 different soils amended with one wood ash. Plant availability was assessed by measuring the biomass and P concentration of corn (Zea mays) L.) plants grown in the greenhouse for 28 d in soil amended with either CaCO₃ (control), wood ash to supply 200 mg kg^?1 total P, or monocalcium phosphate (MCP) to supply 200 mg kg^?1 total P and CaCO₃. Both corn growth and P uptake were highest in the MCP treatments, intermediate in the wood ash treatments, and lowest in the controls for all soil types. The soil property which seemed to have the greatest influence on P availability was pH buffer capacity. The soils with the greatest capacity to buffer OH additions also tended to exhibit the greatest absolute P uptake from wood ash-amended soils and the greatest P uptake relative to that from MCP-amended soils. The ability of soil test extractants to predict uptake of P in the three soil treatments was examined. A buffered ammonium acetate extradant overestimated P availability in the ash-amended soils relative to the MCP-amended soils. An unbuffered, acid, fluoride-containing extract provided a measure of P levels that was consistent with P uptake from all soil treatments. In this study the predictive relationship was as follows: P uptake = 0.017× (Bray P, mg kg^?1) + 1.19; r = 0.81.     

Evaluation of fly ash as a soil amendment for the Atlantic Coastal Plain: II. Soil chemical properties and crop growth

Crop yields in the Atlantic Coastal Plain of the U.S.A. are limited by the low moisture-holding capacities of the sandy soils common to the region. Corn was grown in a Hammonton loamy sand soil amended with fly ash (0, 5, 10, 20, 30, and 40%) to determine if the ash rates required to improve soil moisture holding capacity would adversely affect plant growth, or soil and plant levels of nutrients and heavy metals. Fly ash increased soil test levels of P, K, Ca, Mg, Mn, Cu, Zn, B, Cd, Cr, Ni, and Pb. Nutrient concentrations in plants grown in the ash-amended soils, except P, Mn, and B, remained within established sufficiency ranges. The 20 and 40% ash rates increased soil soluble salt (EC) levels from 0.2 to 1.1–1.5 and 1.7–2.1 mmho cm^?1, soil pH from 5.6 to 6.0–6.4 or 6.3–6.9, and extractable B from 0.2 to 2.2–5.9 and 2.2–9.0 mg kg^?1. Fly ash reduced corn germination, delayed seedling emergence, and reduced root and shoot dry weights. Plant B concentrations at the 40% ash rate were in the phytotoxic range (136–189 mg kg^?1). Management practices that allow for pre-leaching of B and soluble salts will likely be required to attain satisfactory corn growth in ash-amended soils.     

Isolation and Optimization of PAH-Degradative Bacteria from Contaminated Soil for PAHs Bioremediation

The aim of the present study was to determine the amount ofcoal fly ash required to stabilize sewage sludge, without causing an adverse effect on the growth of Zea mays L. seedlings (corn) in a loamy soil receiving the ash-sludge mixtures amendment. Sludge was stabilized by mixing with fly ash at an amendment rate of 0, 5, 10, 35 and 50% (w/w) beforeundergoing a short fermentation period to produce a range of ash-sludge fertilizer product. Each mixture was then mixed with a loamy soil at either 1:1 or 1:5 ash-sludge mixture:soil(v/v). Soil pH, electrical conductivity (EC), and solubleCa, Mg and B contents increased while soluble NH₄-N,PO₄-P, K, Cd, and Ni contents decreased with anincrease in ash amendment rate. Dry weight yields of potsreceiving 1:5 ash-sludge:soil mixture (v/v) weresignificantly higher than their counterparts with asoil-mixing ratio of 1:1 (v/v). The highest yields were obtainedat 5 and 10% ash-sludge mixture amended soil at 1:5 soilmixing ratio. Nevertheless, the yield at 35% ash-sludgeamended loamy soil at 1:1 v/v was still higher than that ofthe control soil with fertilizer treatment. The nutrientcontent of corn seedlings was higher at 35% and 10% ash-sludge mixture amended soil at 1:1 v/v, and 5% and 10% at1:5 v/v than other treatments. Zinc concentrations of cornseedlings increased while B decreased with the decreasingamounts of fly ash added. Hence, the present experimentdemonstrates the beneficial effects of the ash-sludgemixture on soil nutrient status and plant root growthenvironment. An ash amendment rate of up to 35% in theash-sludge mixture would not have any adverse effects onplant production even at a high soil-mixing volume of 1:1(v/v), but an addition of 5% to 10% ash-sludge mixture at1:5 (v/v) produced the optimum condition for corn seedlingsgrowth. The results support the use of coal fly ash as astabilizing agent for sewage sludge and the product couldbe used for land application.     

Weathered Fly Ash Does Not Affect Soil And Biosolid Carbon Mineralization

Fly ash and biosolid wastes can be mixed and applied to soil as a means of disposal. A significant decline in soil respiration following waste application indicates restricted activities of functional microbial populations. Weathering decreases salinity and neutralizes alkalinity in fly ash, but there is little information on the effects of unweathered fly ash and biosolid mixtures on soil carbon (C) mineralization. The objective of this study was to determine the effects of a weathered fly ash–limestone scrubber residue (LSR) mixed with an aerobically digested biosolid on soil respiration in a laboratory incubation study. Biosolids significantly increased carbon dioxide (CO₂) production (p < 0.05), but up to 6.75% (w/w) fly ash did not. Mean total C mineralization was 770 mg CO₂‐C kg^?1 soil in the control and 3,810 mg CO₂‐C kg^?1 soil in the 6.75% (w/w) biosolid treatment. Fly ash with neutral pH and low salinity appears unlikely to affect soil and biosolid C mineralization.     

The Accumulation of Boron in Agropyron elongatum Grown in Coal Fly Ash and Sewage Sludge Mixture

A greenhouse pot experiment was conducted to investigate the boron (B) release capacity of coal fly ash and sewage sludge mixtures, and the accumulation of B in Agropyron elongatum after two consecutive growing seasons. Sludge was amended with fly ash at application rates of 0, 5, 10, 35, and 50% (w/w), and each mixture was then mixed with a loamy soil at either 1:1 or 1:5 (v/v). Both water soluble B (WS-B) and hot water soluble B (HWS-B) increased with increasing fly ash amendment rate. Shoot B concentrations also increased significantly according to the rate of ash amendment. The ash-sludge mixture improved plant growth with the highest total dry weight yield at 10% ash amendment rate. Boron toxicity symptoms in leaf tips were observed at 35% and 50% ash amendment rate at both soil mixing ratios. Hot water soluble B and WS-B decreased significantly after consecutive cropping of Agropyron especially at low ratio of mixure with soil i.e., 1:5 (v/v). However, soil available B contents at ≥ 35% ash application rate and 1:1 (v/v) soil mixing ratio were still excessive for normal plant growth, suggesting that deleterious effects on plant growth would be experienced in later seasons owing to the high amounts of residual B.     

Uptake of multielements by corn from fly ash-compost amended soil

Fly ash was collected from a coal-fired power plant in and near the U.S. Department of Energy Savannah River Site to study the feasibility of the application of fly ash compost mixture to soils for the availability and uptake of various elements by corn (Zea mays L.). The crop was grown in potted Ogeechee sandy loam soil using eight treatments: soil alone, soil amended with 15% compost, and soil amended with 2, 5, 10, 15, 20 and 25% of fly ash-amended compost. It was observed that 20–25% fly ash and compost soil ratio treatments generally increased plant growth and the yield. The plant uptake of K, Mn, and Cu increased with increasing percentages (2–25%) of fly ash+compost: soil ratios. The total content of K in plants was positively correlated with the dry matter yield of corn. This study indicates that the application of fly ash blended with compost to soil is beneficial to corn production without causing any deleterious effects on plant growth and plant composition.     

Zinc,copper, and nickel availabilities as determined by soil solution and DTPA extraction of a sludge‐amended soil

Abstract

Extracting sludge‐amended soil with DTPA does not always give a reliable measure of plant‐available heavy metals. The major purpose of this greenhouse pot study was to help explain why. Two anaerobically digested sludges from sewages treated with either Ca(OH)₂or FeCl₃were applied to 3‐kg samples of a Mollic Albaqualf previously limed with Ca(OH)₂rates of 0, 2.5, and 10g/pot that resulted in pHs in the check pots of 5.4, 6.2, or 7.7 after the first harvest. Sludge rates provided 0, 200, 40, 800, and 1600 mg Zn kg^‐1of soil. Two consecutive crops of soybeans (Glycine MaxL.) were grown for 42 d each in the greenhouse. DTPA‐extractable, soil‐solution, and plant concentrations of Cu²⁺, Ni²⁺, and Zn²⁺were measured.

Dry matter yields were depressed due to salt toxicity, while DTPA‐extracted Cu²⁺correlated with plant uptake of Cu²⁺for both sludges. DTPA‐extracted Ni²⁺also correlated with plant Ni²⁺from the Ca(OH)₂‐sludge‐amended soil, although DTPA‐extracted Ni²⁺did not correlate with plant uptake of Ni²⁺from the FeCl₃‐sludge‐amended soil, DTPA‐extracted Zn did not correlate with plant uptake of Zn²⁺from any sludge‐amended soil. Soil‐solution composition correlated with plant uptake of Cu²⁺and Ni²⁺in both sludges; it also correlated with plant uptake of Zn²⁺from FeCl₃‐sludge‐amended soil but not from Ca(OH)₂‐sludge‐amended soil. DTPA extraction probably failed with Ni²⁺and Zn²⁺because of (i) its ineffectiveness at low pH, (ii) the inability of DTPA to buffer each soil extract near pH 7.3, and (iii) increased amounts of soluble chelated micronutrients at higher sludge rates and higher soil pHs. Soil‐solution composition seemed to fail only where micronutrient cations in solution probably were present largely as organic chelates     

Effect of Coal Combustion By-products on Phosphorus Runoff from a Coastal Plain Soil

Coal combustion by-products can lower soil phosphorus (P) solubility, but few studies have assessed their effect on runoff P. A soil with elevated P content was amended with fluidized bed combustion ash, flue gas desulfurization gypsum, and anthracite refuse ash at rates of 0–40 g kg^?1 soil, and runoff from small plots was monitored over 3 years. In the first year, by-products lowered dissolved P in runoff by up to 47% below the untreated control; however, effects did not persist into the remaining years of the study. Total P losses were not significantly affected by coal combustion by-products, likely because of elevated particulate P losses. Water-extractable P was up to 40% less in treated soils than in untreated soils across the 3 years. Results demonstrate that although coal combustion by-products readily lower P solubility in soils, their impact on P losses in runoff can be undermined by erosional processes.     

Coal Fly Ash and Phospho‐gypsum Mixture as an Amendment to Improve Rice Paddy Soil Fertility

Abstract

Rice is a plant that requires high levels of silica (Si). As a silicate (SiO₂) source to rice, coal fly ash (hereafter, fly ash), which has an alkaline pH and high available silicate and boron (B) contents, was mixed with phosphor‐gypsum (hereafter, gypsum, 50%, wt wt^?1), a by‐product from the production of phosphate fertilizer, to improve the fly ash limitation. Field experiments were carried out to evaluate the effect of the mixture on soil properties and rice (Oryza sativa) productivity in silt loam (SiL) and loamy sand (LS) soils to which 0 (FG 0), 20 (FG 20), 40 (FG 40), and 60 (FG 60) Mg ha^?1 were added. The mixture increased the amount of available silicate and exchangeable calcium (Ca) contents in the soils and the uptake of silicate by rice plant. The mixture did not result in accumulation of heavy metals in soil and an excessive uptake of heavy metals by the rice grain. The available boron content in soil increased with the mixture application levels up to 1.42 mg kg^?1 following the application of 60 Mg ha^?1 but did not show toxicity. The mixture increased significantly rice yield and showed the highest yields following the addition of 30–40 Mg ha^?1 in two soils. It is concluded that the fly ash and gypsum mixture could be a good source of inorganic soil amendments to restore the soil nutrient balance in rice paddy soil.     

Effect of Zinc × Boron Interaction on Plant Growth and Tissue Nutrient Concentration of Corn

ABSTRACT

A pot experiment was conducted in a greenhouse on a calcareous soil (fine, mixed, mesic, Fluventic Haploxerepts) to study the interaction of zinc (Zn) and boron (B) on the growth and nutrient concentration of corn (Zea mays L.). Treatments consisted of a factorial arrangement of seven levels of B (0, 2.5, 5, 10, 20, 40, and 80 mg kg^{? 1}as boric acid), two sources of Zn [zinc sulfate (ZnSO₄ · 7H₂O) and zinc oxide (ZnO)], and three levels of Zn (0, 5, and 10 mg kg^{? 1}) in a completely randomized design with three replications. Plants were grown for 70 d in 1.6 L plastic containers. Applied Zn significantly increased plant height and dry matter yield (DMY) of corn. Source of Zn did not significantly affect growth or nutrient concentration. High levels of B decreased plant height and DMY. There was a significant B × Zn interaction on plant growth and tissue nutrient concentration which were rate dependent. In general, the effect of B × Zn interaction was antagonistic on nutrient concentration and synergistic on growth. It is recommended that the plants be supplied with adequate Zn when corn is grown in high B soils, especially when availability of Zn is low.     

Evaluation of Coal Fly Ash-Based Synthetic Aggregates as a Soil Ameliorant for the Low Productive Acidic Red Soil

A potential new way of producing coal fly ash-based granular synthetic aggregates (CSA) using waste coal fly ash (CFA), paper waste, lime, and gypsum and their utilization as a soil ameliorant to improve crop production in low productive acidic red soil in Okinawa, Japan were studied. The red soil was amended with CSA at three different mixing ratios (i.e., CSA/soil—1:1, 1:5, and 1:10) for the cultivation of Brassica rapa var. Pervidis commonly known as Komatsuna, and the physico-chemical parameters of CSA–soil mixtures and plant growth were analyzed. Incorporation of CSA to the red soil improved the physical and chemical properties of the soil such as water holding capacity, hydraulic conductivity, bulk density, pH, exchangeable cation concentration, cation exchange capacity, particle size distribution, soil pH, electrical conductivity, and carbon content. CSA amendment at ratios of 1:1, 1:5, and 1:10 decreased bulk density by 29.39%, 14.28% and 11.11%, respectively, compared to the original red soil. The acidic pH of the red soil (5.12) was increased to 7.13 and 6.37 by CSA/soil ratios of 1:5 and 1:10, respectively. CSA amendment in soil at 1:5 ratio increased water holding capacity, saturated hydraulic conductivity, electrical conductivity, cation exchange capacity, carbon, potassium (K), magnesium (Mg), and calcium (Ca) content by 0.06 kg kg^?1, ten times, 15.95 mS m^?1, 1.76 cmol_c kg^?1, 6.07 g kg^?1, 0.42 g kg^?1, 0.24 g kg^?1, and 3.38 g kg^?1, respectively, in comparison to the original red soil. Heavy metal contents of the CSA–soil mixtures were below the maximum pollutant concentrations suggested by the US Environmental Protection Agency. Moreover, Na, K, Mg, Ca, copper (Cu), and zinc (Zn) contents in the CSA–soil mixtures increased in comparison with the original red soil. CSA amendment in soil at the ratio of 1:5 and 1:10 resulted in an increase in plant height and plant fresh weight by three and 12 times, respectively, and there was increase in N, K, Mg, Ca, Cu, and Zn contents of the shoots. The results suggest that utilization of eccentric CSA as soil amendment agent can be regarded as an effective waste management practice.     

Novel Fertilizer as an Alternative for Supplying Manganese and Boron to Soybeans

Soybean (Glycine max) commonly experience Mn deficiencies in the coarse-textured soils of Coastal Plain Virginia, especially under high pH conditions. The objective of this study was to investigate the ability of a novel coated fertilizer to provide Mn and B to soybeans in soils where Mn deficiency is common and B deficiency, although far less common than with Mn, is possible. A 60-d greenhouse experiment was conducted with three treatments: control, uncoated KCl, and Mn +B coated KCl applied to Bojac and Dragston sandy loams. Soil and whole plant tissue samples were collected throughout the experiment. Bojac and Dragston soils treated with the coated KCl contained 12.0 mg kg^?1 and 15.8 mg kg^?1 more Mehlich 1 – Mn, 21.7 mg kg^?1 and 23.0 mg kg^?1 more Mehlich 3 Mn, and 4.5 mg kg^?1 and 4.6 mg kg^?1 CaCl₂ – Mn than the control and uncoated KCl, respectively. Coated KCl increased above ground tissue Mn by 42.9 mg kg^?1 compared to the control and the uncoated KCl treatments in the Bojac soil, while the Dragston soil showed no significant differences in Mn tissue concentration between treatments. Above ground tissue, Mn was much lower in the Dragston soil than the Bojac, probably due to greater organic matter which chelates Mn keeping it less plant available. Boron concentrations did not differ in plant tissue or soil, regardless of the extraction method. Results indicate that the coated KCl product could consistently provide increased Mn concentration in acidic sandy soils despite varying levels of organic matter, but is not effective for B.     

Increase of Available Phosphorus by Fly‐Ash Application in Paddy Soils

Abstract

Fly ash from the coal‐burning industry may be a potential inorganic soil amendment to increase rice productivity and to restore the soil nutrient balance in paddy soil. In this study, fly ash was applied at rates of 0, 40, 80, and 120 Mg ha^?1 in two paddy soils (silt loam in Yehari and loamy sand in Daegok). During rice cultivation, available phosphorus (P) increased significantly with fly ash application, as there was high content of P (786 mg kg^?1) in the applied fly ash. In addition, high content of silicon (Si) and high pH of fly ash contributed to increased available‐P content by ion competition between phosphate and silicate and by neutralization of soil acidity, respectively. With fly‐ash application, water‐soluble P (W‐P) content increased significantly together with increasing aluminum‐bound P (Al‐P) and calcium‐bound P (Ca‐P) fractions. By contrast, iron‐bound P (Fe‐P) decreased significantly because of reduction of iron under the flooded paddy soil during rice cultivation. The present experiment indicated that addition of fly ash had a positive benefit on increasing the P availability.     

Phosphorus Availability and Early Corn Growth Response in Soil Amended with Turkey Manure Ash

Incinerating turkey manure is a new option in the USA to generate renewable energy and to eliminate environmental problems associated with manure stockpiling. Incineration produces turkey manure ash (TMA) with a nutrient content of 43 g phosphorus (P) kg^?1 and 100 g potassium (K) kg^?1. We conducted a greenhouse pot study using a low P (6 mg kg^?1) and high K (121 mg kg^?1) soil/sand mixture with a 7.0 pH to evaluate early growth response of corn (Zea mays L.) to TMA. A control and five rates based on P (5.6, 10.9, 16.5, 21.9, and 27.2 mg kg^?1) and respective K contents in TMA were compared with triple-superphosphate and potassium chloride fertilizer. Plant height and stalk thickness at 24 and 31 days after emergence (DAE) were greatest with the fertilizer, but no differences were detected at the final sampling (52 DAE). Regardless of nutrient source, plant biomass increased with P rate. Because of faster initial plant development, corn dry matter 52 DAE was 15 to 20% greater with fertilizer than with TMA. Corn tissue P concentration was greater with TMA than with fertilizer, but P uptake was similar. Tissue micronutrient concentrations were greatest for the control. Bray 1 P appeared to extract excessive amounts of P in TMA-amended soil, whereas soil P levels with the Olsen extractant provided an estimate of plant-available P that was consistent with plant response. Based on this first approximation, we conclude that TMA is a potential source of P for field crops. Field studies are required to determine recommended application rates.     

Nutrient dynamics,dehydrogenase activity,and response of the rice plant to fertilization sources in an acid lateritic soil

Abstract

Rice variety IR 36, grown under flooding, was studied in 1998 to determine the effects of fly ash, organic, and inorganic fertilizers on changes in pH and organic carbon, release of nutrients (NH₄ ⁺-N, Bray's P, and NH₄OAc K), and dehydrogenase activity in an acid lateritic soil at 15-day intervals. Application of fly ash at 10?t?ha^?1 alone did not improve the availability of NH₄ ⁺-N, or P, as well as the rice grain yield. Availability of NH₄ ⁺-N (35.3–36.9?mg?kg^?1), and P (12.3–14.6?mg?kg^?1) at 15 days after transplanting, and rice grain yields (48.0–51.7?g per pot) were similar under the various fertilization sources such as inorganic fertilizer alone, inorganic fertilizer?+?fly ash or inorganic fertilizer?+?green manure?+?fly ash. Mean dehydrogenase activity was the highest (8.47?µg triphenyl formazon g^?1 24?h^?1) under the mixed fertilization treatments with green manure. At the end of the cropping season (75 days after transplanting), pH, organic carbon, and dehydrogenase activity were higher under the mixed fertilization treatments involving green manure by 3, 15 and 154%, respectively, compared with the inorganic fertilizer alone.     

Formulation of Environmentally Sound Waste Mixtures for Land Application

Major impediments to the land application of coal combustion byproducts (fly ash) for crop fertilization have been the presence of heavy metals and their relatively low and imbalanced essential nutrient concentration. Although nutrient deficiencies, in particular N, P, and K, may be readily augmented by adding organic wastes such as sewage sludge and animal manure, the indiscriminate application of mixtures to crops can cause excessive soil alkalinity, imbalanced nutrition (P, Mg), phytotoxicities (B, Mn, ammonia, nitrite), and unspecified contamination of the food chain by elements such as As. In this study, nutrient availability data and linear programming (LP) were used to solve these problems by formulating fly ash-biosolid triple mixtures which complied with both plant and soil fertilization requirements, and met existing U.S.A. environmental regulations for total As application in sewage sludge (EPA-503). Thirteen different fly ash samples were LP-formulated with sewage sludge, poultry manure, CaCO₃, and KCl to yield 13 unique mixtures, which were then evaluated in greenhouse pot experiments. Results indicated that normal growth and balanced nutrition of sorghum (Sorghumbicolor L.) and soybean (Glycine max (L.) Merr.) crops were achieved in all mixtures, comparable to a balanced fertilizer reference treatment, and significantly better than the untreated control. Phytotoxic levels of B, NH₃, NO₂ ^-, overliming problems, and excessive As levels which were previously encountered from indiscriminate use of these waste materials, were all well controlled by LP-formulated mixtures. Most fly ash quantities in mixtures were limited by either available B (< 4 kg ha^-1) or total As (< 2 kg ha^-1) restrictions during formulation, while the most alkaline fly ash was limited by its high calcium carbonate equivalence (CCE = 53.9%). These results confirmed that fly ash land application should not be at arbitrary fixed rates, but should be variable, depending on the soil, crop, and particularly the fly ash chemistry.     

Effect of coal fly ash and co‐composted sewage sludge on emergence and early growth of cover crops

Abstract

Fly ash, a by‐product of coal combustion, is often stored in landfills. Stabilization of fly ash deposits can be hindered by phytotoxic levels of B and soluble salts in the ash. Two greenhouse studies were conducted with the objective of improving cover crop establishment on landfills containing fly ash. In one experiment, eight cover crop species were screened for tolerance to fly ash and fly ash‐amended soil, as measured by seedling emergence and early shoot growth. Hairy vetch, red clover, and tall fescue were identified as having the best potential for stabilization of fly ash deposits. Another experiment determined if amending fly ash with a co‐compost, produced from municipal refuse and sewage sludge, would improve the establishment and growth of tall fescue and Korean lespedeza. The co‐compost had no effect on fescue alone, but increased emergence and early growth of lespedesa and a fescue‐lespedeza mixture.     

Upper and lower levels of boron for cotton and wheat as influenced by calcium carbonate

Abstract

Pot studies were conducted to study effect of the boron (B) levels (0, 0.12, 0.25, 0.50, 0.75, 1.0, 2.0 3.0, 4.0, 5.0 and 10?mg?B?kg^?1) and calcium carbonate (CaCO₃) (0, 1.25, 2.5 and 5.0%) on cotton and wheat crops in cropping system. In absence of CaCO_3, reduced growth of cotton and wheat were observed when B was applied @ 2.0?mg?kg^?1 soil. Necrosis of leaves in cotton and purple coloration of plumule in wheat was observed @ 10.0?mg?B?kg^?1. Irrespective of CaCO₃, 0.57 and 7.67?mg?kg^?1 Hot Water Soluble B (HWS-B), 62 and 940?mg?kg^?1 B dry matter (DM) of leaves, 45 and 210?mg?B?kg^?1 DM of petioles and 20 and 51?mg?B?kg^?1 DM of sticks, produced 90 and 50%of the maximum dry matter yield (DMY) of cotton, respectively. The values for wheat were 0.66 and 6.71?mg HWS-B kg^?1, 7.94 and 27.0?mg?B?kg^?1 grain and 15.3 and 170?mg?B?kg^?1 straw, respectively.     

Nitrogen Mineralization in Soils Treated with Fly Ash–Amended Wastewater Sludges

Abstract

Alkaline‐treated wastewater sludges with varying doses of fly ash were added to a clay soil at rates equivalent to 100 t (dry weight) raw sludge ha^?1 soil, and the variations in ammonium, nitrate, and total nitrogen contents were monitored throughout an incubation period of 360 days at 28°C. The results showed that inhibition of organic nitrogen mineralization occurred in soil amended with fly ash–containing sludge during the first 90 days of incubation. After the total incubation period of 360 days, the inhibition effects of alkaline sludge amendments totally disappeared. In fact, mineralization was enhanced in alkaline pasteurized sludges containing 80% and 120% fly ash. The overall results indicated that application of sludges amended with fly ash may prolong the use (3 to 6 months) of nitrogen from the organic nitrogen pool in sludge.     

Nitrogen transformation from three soil organic amendments in a sandy soil

Abstract

A sandy soil was amended with various rates (20 – 320 g air-dry weight basis of the amendments per kg of air-dry soil) of chicken manure (CM), sewage sludge (SS), and incinerated sewage sludge (ISS) and incubated for 100 days in a greenhouse at 15% (wt/wt) soil water content. At the beginning of incubation, NH₄-N concentrations varied from 50 – 280 mg kg^?1 in the CM amended soil with negligible amounts of NO₃-N. Subsequently, the concentration of NH₄-N decreased while that of NO₃-N increased rapidly. In soil amended with SS at 20 – 80 g kg^?1 rates, the NO₃-N concentration increased sharply during the first 20 days, followed by a slow rate of increase over the rest of the incubation period. However, at a 160 g kg^?1 SS rate, there were three distinct phases of NO₃-N release which lasted for160 days. In the ISS amended soil, the nitrification process was completed during the initial 30 days, and the concentrations of NH₄-N and NO₃-N were lower than those for the other treatments. The mineralized N across different rates accounted for 20 – 36%, 16 – 40%, and 26 – 50% of the total N applied as CM, SS, and ISS, respectively.