易降解有机质含量对黄瓜秧堆肥腐熟和氮损失的影响

蔬菜废弃物无害化处理,尤其对于集约化蔬菜产地,缺乏适用技术,易污染环境,浪费资源,甚至造成后续安全隐患。为实现蔬菜废弃物的安全高效转化,该试验以黄瓜秧为堆肥主原料,以玉米秸秆、淀粉和尿素为调理剂,在控制混合堆肥物料初始碳氮比为25,物料水分质量分数为60%,总物料质量相同的条件下,分析易降解有机质(除木质纤维素之外的有机质)比例对堆肥腐熟进程和氮素损失的影响。试验设置添加易降解有机质的质量分数分别为27%(T1)、36%(T2)、45%(T3)、51%(T4)4个处理,利用自制密闭式堆肥反应器研究了随堆肥进行,不同处理温度、物料损失、有机质降解和二氧化碳释放、p H值、电导率(electrical conductivity,EC)、发芽率指数(germination index,GI)的变化情况,并同时分析了氨气挥发速率、累积排放量和氮素损失率等。研究结果显示:随着初始混合物料中易降解有机质的增加,堆体的最高温度呈现出先升高后降低的趋势,但根据物料的p H值、EC和GI值判断,易降解有机质比例过高会影响堆肥的腐熟过程,其比例不宜超过45%,其中T3的最高温度最高,高达71.4℃,且有机质减少量和CO2累积排放量最高,表明T3最利于堆肥的起爆反应和无害化目标的实现;然而,易降解有机质的增加会伴随氮素损失,尤其是氨气挥发损失量的增加,其中T3氨气损失累积量最大(380.29 mg),T4的氮素损失率最高(36.01%),即物料中的木质纤维素有利于减少氮素的损失。综上,物料中易降解有机质质量分数为45%最利于堆肥的高温实现,同时对腐熟的影响较小,但氮素损失率高,因此实际生产中可额外添加木质纤维素类膨胀剂,改良物料的物理结构和理化特点,从而在实现高温的基础上减少氮素的损失。     

Low soil nitrate levels from golf course fairways related to organic matter sink for nitrogen

Abstract

Nitrogen (N) is applied to golf course fairways at rates similar to that applied to corn. This appears excessive since N fertilization of corn is approximately equal to the amount of N removed at harvest, while typically no harvest occurs for turf. This study was done to determine soil nitrate (NO₃) concentrations from newer and older golf courses and to help determine the fate of fertilizer N. Soil samples were taken every other month in 1995 from two golf courses in southeastern Louisiana to a 3 m depth and from six sites monthly in 1996 to a 1‐m depth. In August 1996, soils were also sampled off of the fairways in areas that were similar to the fairways, but were unfertilized. All soils were analyzed for water‐extractable NO₃, and a comparison was made of soil organic matter (OM) and N contents from fertilized and unfertilized areas. Results indicated, with few exceptions, low levels of NO₃ throughout the profile, excluding the upper surface soils. Generally, surface soils measured <15 mg kg^‐1 NO₃‐N while soils at depths >30 cm were <3 mg kg^‐1 NO₃‐N. The fertilized fairways had 0.151% soil N versus the adjacent unfertilized areas of 0.108% N. The fertilized soils had 1,930 kg more N per 30 cm thick hectare slice than did the unfertilized soils’ equivalent to 10 years of N fertilization. Organic matter was also higher from the fertilized soils than from the unfertilized soils (1.61% versus 1.03%). It appeared much of the N applied to turf throughout the years had been captured by the OM sink. Prior to golf course development, conditions are generally not as conducive for soil OM buildup as compared to the golf‐course regime of adequate N fertilization and no harvests. Some of the high requirement for N of the golf‐course fairways of this study were likely related to the N requirement of a soil OM fraction that grew as the golf course aged.     

Effects of sodium carbonate on carbon and nitrogen mineralisation of organic matter added to soil

An experiment was carried out to study effects of 0.25%, 0.50% and 1.0% Na₂CO₃ on CO₂ evolution, nitrogen mineralisation, losses of carbon and nitrogen and humus composition of added gulmohur (Delonix regia) leaves. The CO₂ evolution was higher under all levels of alkalinity than in the controls, being highest at 0.5% Na₂CO₃. Although the process of ammonification was not inhibited at any concentration, the process of nitrification was completely inhibited at 1.0% Na₂CO₃. The losses of carbon and nitrogen and the ratio of humic to fulvic acids increased with increased alkalinity.     

Influence of tillage, crop rotation and nitrogen fertilization on soil organic matter and nitrogen under rain-fed Mediterranean conditions

The long-term effects of cropping systems and management practices on soil properties provide essential information for assessing sustainability and environmental impact. Field experiments were undertaken in southern Spain to evaluate the long-term effects of tillage, crop rotation and nitrogen (N) fertilization on the organic matter (OM) and mineral nitrogen (N_min) contents of soil in a rain-fed Mediterranean agricultural system over a 6-year period. Tillage treatments included no tillage (NT) and conventional tillage (CT), crop rotations were of 2 yr with wheat (Triticum aestivum L.)-sunflower (Helianthus annuus L.) (WS), wheat-chickpea (Cicer arietinum L.) (WP), wheat-faba bean (Vicia faba L.) (WB), wheat-fallow (WF), and in addition, continuous wheat (CW). Nitrogen fertilizer rates were 50, 100, and 150 kg N ha⁻¹. A split-split plot design with four replications was used. Soil samples were collected from a depth of 90 cm at the beginning of the experiment and 6 yr later. Soil samples were also collected from a depth of 30 cm after 4 yr. These samples, like those obtained at the beginning of the experiment, were subjected to comprehensive physico-chemical analyses. The soil samples that were collected 6 yr later were analyzed for OM, NH₄⁺---N and NO₃⁻---N at the 0–30, 30–60 and 60–90 cm soil depths. The tillage method did not influence the OM or N_min contents of the soil, nor did legume rotations increase the OM content of soil relative to CW. A longer period may have been required for differences between treatments to be observed owing to the small amount of crop residue that is returned to soil under rain-fed conditions of semi-arid climates. The WF rotation did not raise the N_min content of the soil relative to the other rotations. The consistent significant interaction between tillage and crop rotation testifies to the differential effect of the management system on the OM content and N status of the soil. The ammonium levels clearly exceeded those of NO₃⁻---N throughout the soil profile. The high N_min content of the soils reveals the presence of abundant N resources that should be borne in mind in establishing N fertilization schemes for crops under highly variable climatic conditions including scant rainfall such as those of the Mediterranean region.     

Influence of organic matter and inorganic fertilizer on the growth and nitrogen accumulation of corn plants

Effects of different nitrogen (N) sources on the growth and N accumulation of corn plants were studied on plots treated with a compost, a leguminous green manure, and a peat, respectively, associated with a chemical N fertilizer. The experiment included seven treatments with a no‐fertilization check and a conventional chemical fertilizer treatment. Whole corn plants were sampled, and total N was analyzed at 22, 33, 56, 77, and 120 days after seeding (DAS). The results showed that compost with an adequate amount of chemical N fertilizer could reach a high dry matter yield and a high N accumulation, even higher than those of the conventional chemical N fertilizer treatment. With green manure, a considerable amount of N was mineralized and utilized by the corn plants for growth and resulted in a good yield. Neither the peat nor the compost alone could supply enough N for the growth of corn plants. There were no significant effect of treatments on the distribution of dry matter yield and N accumulated in various organs. The crop growth rate of the corn plants of different treatments were significantly different at the vegetative growth stage, however, there were no significant difference during the grain filling period. The apparent N recovery of various treatments were between 0.22 to 0.51 kg N for each kg N applied.     

Influence of soil compaction on carbon and nitrogen mineralization of soil organic matter and crop residues

 We studied the influence of soil compaction in a loamy sand soil on C and N mineralization and nitrification of soil organic matter and added crop residues. Samples of unamended soil, and soil amended with leek residues, at six bulk densities ranging from 1.2 to 1.6 Mg m^–3 and 75% field capacity, were incubated. In the unamended soil, bulk density within the range studied did not influence any measure of microbial activity significantly. A small (but insignificant) decrease in nitrification rate at the highest bulk density was the only evidence for possible effects of compaction on microbial activity. In the amended soil the amounts of mineralized N at the end of the incubation were equal at all bulk densities, but first-order N mineralization rates tended to increase with increasing compaction, although the increase was not significant. Nitrification in the amended soils was more affected by compaction, and NO₃ ^–-N contents after 3 weeks of incubation at bulk densities of 1.5 and 1.6 Mg m^–3 were significantly lower (by about 8% and 16% of total added N, respectively), than those of the less compacted treatments. The C mineralization rate was strongly depressed at a bulk density of 1.6 Mg m^–3, compared with the other treatments. The depression of C mineralization in compacted soils can lead to higher organic matter accumulation. Since N mineralization was not affected by compaction (within the range used here) the accumulated organic matter would have had higher C : N ratios than in the uncompacted soils, and hence would have been of a lower quality. In general, increasing soil compaction in this soil, starting at a bulk density of 1.5 Mg m^–3, will affect some microbially driven processes. Received: 10 June 1999     

Net nitrogen mineralization from light- and heavy-fraction forest soil organic matter

Fine surface soil ( < 2 mm) from four sites in Oregon and Washington and three in Costa Rica was separated by repeated notation in NaI solution (sp. gr. < 1.2, 1.4, or 1.6 g cm^?3) into a light and a heavy fraction. Most organic matter in the light fractions consisted of partly-decomposed root fragments and other plant and microbial remnants and most in the heavy fractions was adsorbed or deposited on mineral surfaces or was protected within organo-mineral microaggregates. The light fraction had a consistently wider C:N ratio than the heavy, and net N mineralization during anaerobic incubation was greater from the heavy than from the light fraction in five of six soils for which both fractions were incubated. Net N mineralization was greater from the heavy fraction than from the whole soil of most sites perhaps because the light fraction immobilized N released from the heavy fraction when they were incubated together. Correlation between net N mineralization (as a proportion of total N) and C:N ratio was negative for the light fraction (r²=0.74) but positive for the heavy fraction (r² = 0.85), suggesting that the C:N ratio does not control the extent to which heavy-fraction N is mineralizable.     

Nitrate leaching: modifying the loss from mineralized organic matter

The impact on nitrate leaching of agronomic practices designed to immobilize nitrogen in autumn and winter was investigated over 4 years. Experimental treatments (reducing tillage depth, incorporating harvest residues, reducing fertilizer N by growing unfertilized grass or by spring-sown rather than autumn-sown crops) were compared with a control treatment in which autumn crops were sown after burning harvest residues, mouldboard ploughing and seedbed preparation. Winter cover cropping was also compared with winter fallowing. In the first year, incorporation of harvest residues or reducing tillage depth significantly decreased nitrate leaching compared with the control. Unfertilized grass did not affect leaching in the first winter but significantly decreased it in years 2 and 3. When winter cover crops were grown, nitrate leaching was never less than that under an autumn-sown cereal, and in the subsequent year leaching could be significantly greater. Winter fallowing caused the most nitrate leaching over the year. In the winter following a spring-sown crop, leaching under an autumn-sown crop greatly increased. Summed over 4 years, most leaching occurred with the winter fallow—spring cropping treatment; it was 18% more than where a winter cover crop preceded the spring crop. Reducing tillage depth or incorporating harvest residues did not significantly decrease leaching. Unfertilized grass ley followed by an autumn-sown cereal in the fourth year was the only treatment that significantly decrease leaching. Unfertilized grass ley followed by an autumn-sown cereal in the fourth year was the only treatment that significantly reduced leaching loss compared with the control. Incorporating harvest residues resulted in a balance between annual N inputs and outputs. All other treatments required substantial net annual N mineralization to balance annual inputs and outputs.     

Effect of pH,organic matter content and nitrate on the evolution of ethylene from soils

The evolution of C₂H₄ from soils was stimulated by air-drying, and still more by oven-drying at 105°C. The quantities evolved were closely correlated with organic matter content, with no significant difference in this relationship between grassland and arable soils, or between topsoil and subsoil. In arable soils only, the quantities of C₂H₄ also increased significantly with decreasing pH. No significant relationship could be found between NO₃^? concentrations in fresh soils and the quantities of C₂H₄ evolved, but for air-dried soils (arable only) there was a significant decrease with increasing NO₃^?. Artificial addition of NO₃^? only partially inhibited the evolution of C₂H₄, even at concentrations an order of magnitude higher than those found in the field. At normal soil concentrations the only effect of NO₃^? seems likely to be a short delay in the achievement of the maximum C₂H₄ concentrations.     

施用控释氮肥对减少稻田氮素径流损失和提高水稻氮素利用率的影响

采用渗漏池模拟研究了洞庭湖区双季稻种植条件下施用控释肥料对氮素径流损失、水稻产量和稻株氮素含量的影响。结果表明,施用等N量控释氮肥 (CRNF) 和70%N量控释氮肥 (70% CRNF) 的处理总氮 (TN) 径流损失量比施用尿素处理 (CF) 分别降低了24.5%和27.2% (P0.05)。主要是施用控释氮肥显著降低了水稻前期 (施肥后10 d内)的径流水中氮素浓度。与施用尿素相比,两种土壤上施用控释肥的早、晚稻产量均明显提高,特别是在河沙泥上,稻谷总产量以70% CRNF处理最高,比尿素处理增产4.95% (P0.05)。控释氮肥能明显提高水稻生长后期的植株和子粒中的N含量;在水稻增产显著的河沙泥上,70% CRNF处理的早、晚稻子粒N含量较CF处理提高了9.4% (P0.05)和23.3%(P0.01);其氮素利用率高于施用全量尿素的CF处理。     

Quantifying soil water effects on nitrogen mineralization from soil organic matter and from fresh crop residues

A loamy sand was incubated with and without addition of carrot leaves at six different water contents ranging from 6% to 20% (g 100 g^-1 dry soil) and N mineralization was monitored during 98 days. We calculated zero- and first-order rates for mineralization in the unamended soil and first-order rates for N mineralization in the residue-amended soil. Although N mineralization was strongly affected by soil moisture, rates were still important at 6% water content (corresponding to permanent wilting point), particularly in the residue-amended soil. Soil water content was recalculated as soil water tension and as percent water-filled pore space (%WFPS) and a parabolic, a logistic and a Gaussian-type function were fitted to the relation between N mineralization rates and water content, %WFPS or pF. Water potential was a less suitable parameter than either %WFPS or water content to describe the soil water influence on N mineralization, because N mineralization rates were extremely sensitive to changes in the water potential in the range of pF values between 1.5 and 2.5. In the residue-amended soil the Gaussian model yielded an optimum %WFPS of 56% for N mineralization, which is slightly lower than optimum values cited in literature. N mineralization in the unamended soil was more influenced by soil water than N mineralization from fresh crop residues. This could be explained by less water limitation of the microbial population decomposing the residues, due to the water content of the residues. The effect of the water contained in the residues was most pronounced in the lowest water content treatments. The water retention curves of both undisturbed and repacked soil were determined and suggested that extrapolation of results obtained during laboratory incubations, using disturbed soil, to field conditions will be difficult unless soil bulk density effects are accounted for, as is the case with the use of %WFPS.     

Influence of foliar phosphorus and nitrogen contents on chemical properties of water extractable organic matter derived from fresh and decomposed sugar maple leaves

The effects of watershed-scale experimental acidification on the macronutrient content and decomposition of sugar maple (Acer saccharum Marsh) leaves were investigated. Bear Brook Watershed in Maine (BBWM) is a paired forest watershed study where the West Bear (WB) watershed has been treated bi-monthly with 1800 eq ha^?1 yr^?1 of (NH₄)₂SO₄ since 1989, and the adjacent East Bear (EB) watershed has acted as a reference. Leaf samples collected from the treated WB watershed had significantly higher concentrations of N and P than leaves from the reference EB watershed. Leaves from both watersheds were decomposed for a 10-day laboratory incubation. Extractable total soluble carbon (C_TS) content of the leaves decreased following decomposition to a greater extent in WB leaves than in EB leaves. Spectroscopic and chromatographic chemical analyses indicated similar chemical properties for the fresh WB and EB WEOM. However, after decomposition, the WB WEOM was more humified as compared to EB WEOM indicating that the watershed treatment resulted in leaves which were more biodegradable than those in the reference watershed. Multi-dimensional fluorescence spectroscopy with parallel factor analysis (PARAFAC) modeled five components: tyrosine-like, three humic substance-like, and terrestrial/anthropogenic associated-like fluorophores. Following decomposition, the relative concentrations of two of the humic-associated components increased to a significantly greater extent for WB than for EB WEOM. These observations were consistent with greater decomposition-related changes to the WEOM from WB samples relative to EB samples. Pearson correlation analysis showed that foliar N and P concentrations were positively correlated with indices of humification. Adsorption of WEOM to goethite and gibbsite was significantly greater for decomposed WB WEOM than EB WEOM. These results demonstrate that greater leaf N and P contents can increase short-term decomposition, accelerate production of more humic-like WEOM, and thereby potentially influence the distribution of organic matter within the soil carbon pool.     

Effect of alternate aerobic and anaerobic conditions on redox potential,organic matter decomposition and nitrogen loss in a flooded soil

The effect of several cycles of varying length of alternate aerobic and anaerobic conditions on redox potential, organic matter decomposition and loss of added and native nitrogen was investigated under laboratory conditions in flooded soil incubated for 128 days. Redox potential decreased rapidly when air was replaced with argon for the short-time cycles, but decreased more slowly where the aerobic period was long enough to permit build-up of nitrate. The minimum redox potential reached during the anaerobic period was generally lower for the longer cycles, but in all cases was low enough for denitrification to occur. Rate of decomposition of organic matter was faster in the treatments with a greater number of alternate aerobic and anaerobic periods. Total N (native and applied) losses as high as 24.3 per cent occurred in the treatment with the maximum number of cycles and with alternate aerobic and anaerobic periods of 2 and 2 days. Increasing the durations of the aerobic-anaerobic periods decreased the loss of N. A maximum loss of 63.0 per cent of applied ¹⁵NH₄-N resulted from the shortest (2 and 2 day) aerobic and anaerobic incubation. For soil undergoing frequent changes in aeration status the only labelled N that remained at the end of incubation was found in the organic fraction. Loss of N may have been even greater if labelled inorganic N had not been immobilized by microorganisms decomposing the added rice straw. The greater loss of N resulting from the 2 and 2 day aerobic-anaerobic incubation shows that, in soils where the redox potential falls low enough for denitrification to occur, increasing the frequency of changing from aerobic to anaerobic conditions will increase the loss of N.     

Increased plant nitrogen loss with increasing nitrogen applied in winter wheat observed with 15nitrogen

Nitrogen (N) fertilizer is generally the most costly input for winter wheat (Triticum aestivum L.) production. Therefore, it was important to maximize fertilizer use efficiency and minimize N losses to the environment. One of the mechanisms responsible for decreased N use efficiency (NUE) was plant N loss. The objectives of this experiment were to determine fertilizer N recovery in winter wheat when produced for forage and grain, and to quantify potential plant N losses from flowering to maturity in winter wheat. Two long‐term (>25 years) winter wheat (Triticum aestivum L.) N rate fertility experiments (Experiment 222 and Experiment 502) were selected to evaluate ¹⁵N fertilizer recovery. Percent ¹⁵N recovery was determined from all microplots in plant tissue at flowering, in the grain, and straw at harvest and in the soil. Fertilizer N(¹⁵NH₄ ¹⁵NO₃) was applied atratesof 0, 45, 90, and 135kg N ha^‐1 in Experiment 222, and 0, 22, 45, 67, 90, and 112 kg N ha^‐1 in Experiment 502. The ratio ofNO₃ ^‐to NH₄ ⁺ in wheat forage at flowering was positively correlated with estimated plant N loss. Estimated plant N loss (total N uptake in wheat at flowering minus N uptake in the grain and straw at maturity) ranged from a net gain of 12 kg N ha^‐1 to a loss of 42 kg N ha^‐1, and losses increased with increasing N applied.     

不同形态氮肥对玉米产量和土壤浸提性有机质的影响

田间条件下,研究了不同形态氮肥(尿素、NH4+-N和NO3--N)对玉米产量、根际和非根际土壤氮和浸提性有机质的影响.结果表明,施氮处理的产量和吸氮量明显高于不施肥处理;施氮处理中,NO3--N和尿素处理开花前吸氮量显著高于NH4+-N处理,产量也略高于NH4+-N处理,但未达到显著水平;不同氮形态处理之间的土壤NH4+-N、NO3--N和浸提性有机碳(EOC)、氮(EON)没有差异;抽雄期EOC最高,与根系生长发育一致,而EON苗期相对最高.可见,在基础肥力较高的黑土上,不同形态氮肥对玉米产量、土壤养分影响不明显.     

Using time domain reflectometry for monitoring mineralization of nitrogen from soil organic matter

The mineralization of nitrogen from soil organic matter is important when one tries to optimize nitrogen fertilization and assess risks of N losses to the environment, but its measurement is laborious and expensive. We have explored the possibilities for monitoring N mineralization directly using time domain reflectometry (TDR). Net N and S mineralization were monitored over a 101‐day period in two layers (0–30 and 30–60 cm) of a loamy sand soil during aerobic incubation in a laboratory experiment. At the same time electrical conductivity of the bulk soil, σ_a, was measured by TDR. A series of calibration measurements with different amounts of KNO₃ at different soil moisture contents was made with the topsoil to calculate the electrical conductivity, σ_w, of the soil solution from σ_a and θ. The actual σ_w was determined from the conductivity of 1:2 soil:water extracts (σ_1:2) with a mass balance approach using measured NO₃^– concentrations, after correction for ions present prior to the addition of KNO₃. The average N mineralization rate in the topsoil was small (0.12 mg N kg^?1 day^?1), and, as expected, very small in the subsoil (0.023 mg N kg^?1 day^?1). In the top layer NO₃^– concentrations calculated from σ_a determined by TDR slightly underestimated measured concentrations in the first 4 weeks, and in the second half of the incubation there was a significant overestimation of measured NO₃^–. Using the sum of both measured NO₃^– and SO₄^2– reduced the overestimation. In the subsoil calculated NO₃^– concentrations strongly and consistently overestimated measured concentrations, although both followed the same trend. As S mineralization in the subsoil was very small, and initial SO₄^2– concentrations were largely taken into account in the calibration relations, SO₄^2– concentrations could not explain the overestimation. The very small NO₃^– and SO₄^2– concentrations in the B layer, at the lower limit of the concentrations used in the calibrations, are a possible explanation for the discrepancies. A separate calibration for the subsoil could also be required to improve estimates of NO₃^– concentrations.     

Influence of metals on solubility of soil organic matter

Treatment of the alkali-soluble organic matter of soil with a cation-exchange resin resin (Amberlite IR 120, H⁺ form) strongly modified the solubility characteristics of the organic matter, even though only part of the metals was removed. Two or more types of sorption sites were involved in the binding of metals by soil organic matter. The Amberlite removable metals interfered with the separation of humic from fulvic acid.     

Recovery of soil organic matter,organic matter turnover and nitrogen cycling in a post-mining forest rehabilitation chronosequence

Recovery of soil organic matter, organic matter turnover and mineral nutrient cycling is critical to the success of rehabilitation schemes following major ecosystem disturbance. We investigated successional changes in soil nutrient contents, microbial biomass and activity, C utilisation efficiency and N cycling dynamics in a chronosequence of seven ages (between 0 and 26 years old) of jarrah (Eucalyptus marginata) forest rehabilitation that had been previously mined for bauxite. Recovery was assessed by comparison of rehabilitation soils to non-mined jarrah forest references sites. Mining operations resulted in significant losses of soil total C and N, microbial biomass C and microbial quotients. Organic matter quantity recovered within the rehabilitation chronosequence soils to a level comparable to that of non-mined forest soil. Recovery of soil N was faster than soil C and recovery of microbial and soluble organic C and N fractions was faster than total soil C and N. The recovery of soil organic matter and changes to soil pH displayed distinct spatial heterogeneity due to the surface micro-topography (mounds and furrows) created by contour ripping of rehabilitation sites. Decreases in the metabolic quotient with rehabilitation age conformed to conceptual models of ecosystem energetics during succession but may have been more indicative of decreasing C availability than increased metabolic efficiency. Net ammonification and nitrification rates suggested that the low organic C environment in mound soils may favour autotrophic nitrifier populations, but the production of nitrate (NO₃^?) was limited by the low gross N ammonification rates (≤1 μg N g^?1 d^?1). Gross N transformation rates in furrow soils suggested that the capacity to immobilise N was closely coupled to the capacity to mineralise N, suggesting NO₃^? accumulation in situ is unlikely. The C:N ratio of the older rehabilitation soils was significantly lower than that of the non-mined forest soils. However, variation in ammonification rates was best explained by C and N quantity rather than C:N ratios of whole soil or soluble organic matter fractions. We conclude that the rehabilitated ecosystems are developing a conservative N cycle as displayed by non-mined jarrah forests. However, further investigation into the control of nitrification dynamics, particularly in the event of further ecosystem disturbance, is warranted.     

Influence of organic matter on selenite sorption by Andosols

Abstract

The influence of soil organic matter on selenite sorption was investigated in the selenite adsorption capacity and the surface particle charge change by ligand exchange reaction using the hydrogen peroxide (H₂O₂) treatment and the ignition treatment of two Andosols. The removal of organic carbon (C) in soils accelerated selenite sorption, implying that organic matter of soils had negative influence on the selenite adsorption on the soils. Positive charge decrease on soil particles, concomitant proton consumption, and release of silicon (Si), sulfate (SO₄ ^2‐), and organic C were observed in selenite sorption by the soils. The development of surface particle negative charge with selenite sorption was smaller in the H₂O₂‐treated soil than in the original soils and was scarcely observed in the ignition‐treated soil. It can be assumed that the increase of negative charge by selenite sorption was attributed to new negative sites borne by released insoluble organic matter and negative charge development directly by selenite sorption was small.