M. Susan Erich

Effect of wood ash application on soil pH and soil test nutrient levels

Abstract The use of wood residue as a fuel source for pulp and paper industries has led to the production of wood ash as by-product. Land spreading is a potentially sound method for the disposal of wood ash, which is an alternative soil liming agent. This study was conducted to determine the effect of wood ash amendment on soil pH and soil test nutrient levels as measured by a pH 3, 1 M NH4OAc extractant. Wood ash and soil mixtures were incubated in the laboratory and then tested to determine soil pH and plant-available nutrient levels. The calcium carbonate equivalence of the ashes used ranged from 26 to 59%, indicating that the acid-neutralizing power of wood ash varies from source to source. The percentage of plant nutrients released from wood ash to soil varied with the particular nutrient. The average nutrient release percentages were: phosphorus (P), 5.7%; potassium (K), 40%; magnesium (Mg), 48%; calcium (Ca), 74%; sodium (Na), 16%. Wood ash application altered the equivalent fraction of K, Mg and Ca in soils. In general, the equivalent fraction of K and Mg decreased, while the equivalent fraction of Ca increased. The soils which had the least initial extractable Ca had the greatest percentage change in K, Mg and Ca equivalent fraction. Wood ash is an acceptable alternative liming agent which also provides modest amounts of P and K to soils.

Characterization of laboratory weathered labradorite surfaces using X-ray photoelectron spectroscopy and transmission electron microscopy

Altered surfaces of labradorite resulting from laboratory weathering at pH 4 and 25°C were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). SEM micrographs showed nonuniform surface alteration of labradorite weathered at pH 3.7 for 415 days. TEM micrographs showed exsolution lamellae of a more calcic-rich and more sodic-rich phase, each averaging approximately 700 a thick. The more calcic phase was preferentially weathered to average depths of 1350 A in excess of the more sodic phase, producing a corrugated surface. The surface roughness caused by preferential weathering of the more calcic phase affects the relative exposure of calcic and sodic phases to the XPS detector. A three-dimensional analysis of possible surface exposures was used to predict the influence of a corrugated surface on XPS measurements. Actual XPS data showed significant Ca depletion, slight Al depletion, slight Si enrichment, and slight Na enrichment relative to unweathered labradorite. Sputter depth profiling with an Ar ion gun showed that surface alteration was significant up to depths of 500 A, similar to the depth of preferential weathering of the more calcic lamellae observed with TEM. Predicted XPS data accounting for the topographic effects of a corrugated surface showed similar trends of Ca depletion, slight Al depletion, slight Si enrichment, and moderate Na enrichment. Furthermore, predicted XPS sputter depth profiles of Ca, Al, Si, and Na were similar to actual sputter depth profiles, indicating that a significant amount of the surface alteration on labradorite can be explained by preferential weathering of the more calcic lamellae, and the subsequent surface roughness effects this has on XPS spectra. Other surface processes such as H+ or H3O+ exchange for Ca, Na, or Al and preferential weathering at sites of excess surface energy (dislocations, twin boundaries, etc.) not accounted for in the predicted XPS data may also contribute to the surface composition of weathered labradorite. Results showing preferential weathering of more calcic-rich lamellae and its effect on XPS spectra indicate the importance of understanding the micro-structure of feldspars used for laboratory weathering studies.

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.

Release of trace elements from wood ash by nitric acid

Currently wood ash is being used as a soil amendment. Its use is regulated based on trace element content. However, no published information exists on solubilities of trace elements in wood ash. We investigated the release of environmentally-significant trace elements (Cd, Cr, Cu, Pb and Zn) from wood ash as a function of pH and of particle size. Wood ash was sampled from three sources in Maine and sieved into <0.5 mm, 0.5–1 mm, and 1–2 mm fractions. Elemental compositions were determined using a HNO3/H2O2 digestion. Sub-samples (1 g) from each of the nine samples (three sources and three size fractions) were reacted with 50 mLs of standardized HNO3 for a week using a range of acid concentrations (0.01–0.25 M) to achieve a range in final pH values. The resulting solutions were filtered and analyzed. The compositions of the three wood ashes varied widely. The dominant elements were Si (9.7–34%), Ca (5.8–21%), K (0.8–5.7%), Al (0.8–4.9%), and Mg (0.5–3.0%). Trace elements were present in the following concentrations ranges: Cd (1.9–12 mg kg−1), Cr (24–92 mg kg−1), Cu (33–75 mg kg−1), and Zn (130–1400 mg kg−1). Both Cd and Zn were released readily from the ashes at final pH values of approximately 6.5 and below. In the final pH range of 3–4, 80–100% of the total Cd and 70–90% of the total Zn was released by the ashes. All three wood ashes showed somewhat different patterns of Cr release. Level of Cr(VI) in a water extract of the ash fractions was found to be a much better predictor of relative Cr solubility than total Cr. Solubility of Cu was low, and Pb was very insoluble. There was little influence of particle size on release of trace elements. The relatively high Cd concentration of wood ash compared with soil, and its relative solubility in wood ash, should be considered in evaluating the potential environmental impact of spreading wood ash on land.

Titrimetric determination of calcium carbonate equivalence of wood ash

Wood ash is a residual material produced during the process of biomass burning for energy. Spreading this material on the land is used as a means of its disposal. Wood ash contains carbonates which react to raise soil pH, and its regulation is based on ash calcium carbonate equivalence (CCE). The procedure suggested by the Association of Official Analytical Chemists (AOAC) for the determination of the CCE of agricultural limestone is routinely used for the determination of the CCE of wood ash samples. This procedure involves heating a weighed amount of sample with HCI and then back-titration of the remaining acid with NaOH. Unlike agricultural limestones, which are largely carbonates, some wood ash samples contain significant amounts of contaminants such as alumino-silicate clays which may consume acidity when heated with HCl. Significant consumption of acidity by alumino-silicates during CCE analysis would cause the determination of artificially high CCE values, as these alumino-silicates would not be expected to neutralize acidity under field conditions. This study investigated whether the AOAC method of CCE determination resulted in reproducible, accurate CCE values when applied to wood ash samples with various amounts of alumino-silicate contaminants. The accuracy of the method was calculated by comparing the CCE values with those obtained from a soil incubation method. Time of heating had little effect on the CCE value obtained. The back-titration step was reproducible from operator-to-operator despite the formation of a white precipitate before the end-point. The CCE values obtained from the titrimetric method were similar to those obtained from a soil incubation method.

Effect of Drying on Phosphorus Distribution in Poultry Manure

Abstract Laboratory drying may alter manure phosphorus (P) distribution. The effects of freeze, air (22°C), and oven (65°C) drying on sequentially fractioned poultry manure P were examined. Higher drying temperatures resulted in lower percentage of dry matter. Increased H2O‐ and decreased sodium bicarbonate (NaHCO3)‐extractable P with drying provided evidence that drying increases poultry manure P solubility. Labile fractions were predominantly inorganic P (Pi), whereas sodium hydroxide (NaOH) and hydrochloric acid (HCl) fractions had significant amounts of organic P (Po). Drying altered H2O‐ and NaHCO3‐extractable Pi but had no consistent effect on Po in these fractions. This work suggests that variations due to drying should be taken into consideration when evaluating manures for P availability or when comparing data in which different drying methods have been utilized.

Enzymatic Quantification of Phytate in Animal Manure

Phytate (inositol hexaphosphate) has been identified as a major organic phosphorus (P) form in soil, animal manure, and other environmental samples. Although a number of methods are available for quantitative isolation and determination of phytate, they are time‐consuming and not amenable to routine analysis. We developed a simple, rapid method for enzymatic determination of phytate in animal manure. Animal manure was extracted by H2O, 1 M hydrochloric acid (HCl), 0.1 M sodium acetate (NaOAc, pH 5.0) with or without 0.05 M ethylenediaminetetraacetate (EDTA), and 0.25 M or 0.5 M sodium hydroxide (NaOH)–0.05 M EDTA. Extracts were diluted (1/10–1/150) and adjusted to pH 5.0 in sodium acetate buffer. The diluted extracts were then incubated at 37 °C for 1 h in the absence and presence of fungal 3‐phytase (PHY) and potato acid phosphatase (PAP). Enzymatic hydrolyzable organic P was calculated as the difference in inorganic P (Pi) between the mixtures with and without enzymes. Our data indicated that enzymatic incubation of properly diluted and pH‐adjusted HCl or NaOH/EDTA extracts released phytate P. The complementary substrate specificity of the two enzymes is considered to enhance the effectiveness of enzymatic hydrolysis. Consequently, we recommend this method of combining PAP and PHY for quantifying phytate P. Additional research is being conducted to verify the effectiveness of this method for general use across a wider range of soils and manures.

Rates and stoichiometry of hornblende dissolution over 115 days of laboratory weathering at pH 3.6–4.0 and 25 °C in 0.01 M lithium acetate

Abstract The rates and stoichiometry of hornblende dissolution were studied in batch reactors in 0.01 M HOAc-LiOAc buffers at pH 3.6–4.0 and 25 °C for three consecutive weathering cycles of 36, 45, and 34 days (total 115 days). The dissolution rates were obtained for two particle size fractions (0.11–0.25 and 0.25–0.50 mm in diameter) with initial surface areas of 0.098 and 0.086 m 2 g −1 , respectively. Results showed that dissolution rates were nonlinear and nonstoichiometric in the early stage of reaction. The rates were greatest in the first cycle, decreased with time, and became more linear and more stoichiometric as the experiment proceeded into the second and third cycles. A very rapid release of Ca during the initial stages of the reaction was due to 0.91% CaCO 3 impurity in the hornblende. Incongruence was greatest in the first cycle (0–36 days) with preferential release of Al, Fe, and Mg relative to Si and greater at higher pH. Stoichiometric dissolution was approached more rapidly at lower pH, suggesting that the extent of reaction is an important factor in attaining stoichiometric dissolution. By the third cycle (82–155 days), at pH 3.6, the reaction appeared to be stoichiometric. Nonstoichiometry resulted in the depletion Al, Mg, and Al, relative to Si with calculated mean depths of depletion of 7, 38, and 67 nm, respectively, at pH 4.0. Most of the depletion occurred during the first cycle (0–36 days). The pH dependence increased after the first cycle and order dependence of release of Si, Mg, and Al with respect to (H + ) during the second and third cycles was not significantly different from the previously reported value of 0.7. For Fe, however, the order dependence was only 0.36, reflecting the lack of stoichiometry at the higher pH values. Comparison of our second cycle data with data for samples that were dried after an initial weathering treatment showed that drying produced higher dissolution rates and more incongruence. The drying effect was greatest for Fe, with an increase in rate by a factor of 5.6 and least for Si with an increase by a factor of 2.1. Air drying appears to cause the surface of the hornblende to revert to a condition similar to unreacted samples. Comparison of data for dissolution in 0.01 M acetate with data obtained in 0.01 M LiCl suggests acetate increases the rate by about a factor of 3–4. The rate at pH 4.0 for total base release was significantly lower than previous results for experiments conducted for

Incubation-derived calcium carbonate equivalence of papermill boiler ashes derived from sludge and wood sources.

The burning of a papermill sludge and wood mixture and landspreading the resulting ash is a potential means of disposal of papermill sludge without the use of valuable landfill space. This study evaluated the effectiveness of ashes derived from a mixture of papermill sludge and wood sources to act as an alternative liming agent. The calcium carbonate equivalence of the material was determined using a 91-day laboratory incubation test with three mineral soils and one organic horizon soil. Application rates of soil-incorporated sludge-ash ranged from 2.30 to 32.2 g per kg soil. Soil pH increased linearly with increasing sludge-ash application rate. The calcium carbonate equivalence of the material varied temporally and the average value ranged from 19% to 28%. The fraction of total P, K and Mg added with the sludge-ash and extracted from the ash-amended soils using an NH4OAc based soil test method were 2.6, 3.8 and 17.6%, respectively. The low soil test extractability of ash-derived plant nutrients suggests that this material would provide only a modest increase in plant available nutrient levels in landspread fields.

Effects of Soil Drying on Soil pH and Nutrient Extractability

A sample set from a field experiment conducted at two sites, a commercial organic potato farm and a conventionally managed experiment station farm, was used to compare the extractability of nutrients in field-moist and air-dried soils. Standard soil characterization methods of the Maine Soil Testing Service were used to determine soil pH and extractable nutrient content. The data were analyzed with Systat using paired t-tests. Air drying decreased soil pH and increased extractability of calcium, micronutrients, and metals. Many of the observed changes were probably a result of increasing surface acidity with drying. Drying increased the extractability of inorganic phosphorus, probably because of disruption of aluminophosphate complexes, particularly in conventionally managed soils, which had received high amounts of inorganic phosphorus fertilizer. Drying also increased the extractability of complexed phosphorus, probably both organically and inorganically complexed phosphorus, and decreased the extractability of potassium, probably by enhancing potassium fixation in clay interlayers.