Aggregate Nitrogen Research Articles

Feasibility of agricultural utilization of river sludge as a planting substrate following treatment with polyacrylamide

Applying river sludge in agriculture is an effective way of recycling the beneficial substances it contains. Polyacrylamide (PAM) is widely used as a sludge dewatering flocculant and soil amendment agent. The objectives of this study were to determine the effects of PAM on sludge and to ascertain whether the PAM-treated sludge can be used as a planting substrate. Pot cultivation, infiltration, and leaching experiments were conducted under sludge treated with different amounts of PAM, and Chinese cabbage was also grown in pot experiments. We evaluated the changes in the nutrient and enzyme activities, aggregate stability, permeability of the sludge, the ability of the sludge to preserve water and nutrients, and Chinese cabbage growth. The results showed that the physiochemical characteristics of the sludge were improved by applying PAM. The pot experiment showed that the contents of alkaline hydrolysable N, NO3−, and NH4+ in PAM-treated sludge were increased significantly (p < 0.05) by PAM additions, and the optimum Chinese cabbage growth occurred with applications of 900 mg kg−1 and 1350 mg kg−1 PAM. The cultivation experiment showed that the catalase, alkaline phosphatase, and invertase activities were improved by adding PAM. The increased available nitrogen content in the sludge increased with the addition of PAM mainly because PAM provided a suitable micro-ecological environment for microorganisms to increase enzyme activity, which thus accelerated nutrient turnover. The infiltration and leaching experiments showed 900 mg kg−1 PAM provided the optimal permeability and aggregate stability, and better water and nutrient preserving effects. PAM improved the aggregate stability of river sludge by absorbing sludge particles to form larger aggregates, which improved the permeability, water, and nutrient preserving capacity of the sludge. Considering the improvement effects of PAM on the available nitrogen content, enzyme activity, aggregate stability, and water holding capacity of sludge while maintaining Chinese cabbage growth, we found that the 900 mg kg−1 PAM application was the best dosage.

X‐ray computed tomography–measured soil pore parameters as influenced by crop rotations and cover crops

AbstractThis study examined the effect of crop rotations and winter cover crops (CCs) on near‐surface pore characteristics of a silty clay loam soil in a 27‐yr no‐till field experiment. The crop rotation treatments included a 2‐yr corn (Zea mays L.)–soybean [Glycine max L. (Merr.)] (CS) rotation and a 4‐yr corn–soybean–oat (Avena sativa L.)–winter wheat (Triticum aestivum L.) (CSOW) rotation. The subplot treatment was CC and no‐CC (fallow). Intact soil cores (7.62 by 7.62 cm) were extracted from each treatment in July 2018 from soybean plots and examined for X‐ray computed tomography (CT)‐measured pore parameters and other soil physical and hydrological properties. Data showed that, compared with fallow, the CC reduced bulk density (ρb) by 6% and increased saturated hydraulic conductivity (Ksat) and water infiltration rate (qs) by 1.5 times. Soils under CSOW rotation had 16, 14, and 4% higher values of soil organic carbon (SOC), total nitrogen (TN), and wet aggregate stability (WAS) compared with those under CS rotation, respectively. The CSOW rotation significantly (P &lt; .05) increased number of CT‐measured pores, number of macropores (&gt;1,000 μm diameter), coarse mesopores (226–1,000 μm diameter), macroporosity, and mesoporosity compared with the CS system. The CT‐measured total porosity, number of macropores, and macroporosity were 43, 34, and 60%, respectively, higher with CC as compared to the fallow plots. The CT‐measured pore parameters were well correlated with soil ρb, Ksat, qs, SOC, TN, and WAS. This study emphasizes that cropping systems that include diverse crop rotations (CSOW) and CC has potential to enhance SOC, pore characteristics, and associated physical and hydrological properties.

Transition of Ethiopian highland forests to agriculture-dominated landscapes shifts the soil microbial community composition

BackgroundLand use changes and related land management practices significantly alter soil physicochemical properties; however, their effects on the soil microbial community structure are still unclear. In this study, we used automated ribosomal intergenic spacer analysis to determine the fungal and bacterial community composition in soils from different land use areas in the Ethiopian highlands. Soil samples were collected from five areas with different land uses, natural forest, eucalyptus plantation, exclosure, grassland and cropland, which had all historically been natural forest.ResultsOur results showed a significant shift in the soil bacterial and fungal community composition in response to land use change. We also identified soil physicochemical factors corresponding to the changes in bacterial and fungal communities. Although most soil attributes, including soil organic carbon, total soil nitrogen, labile P, soil pH and soil aggregate stability, were related to the change in bacterial community composition, the total soil nitrogen and soil organic carbon had the strongest relationships. The change in fungal community composition was correlated with soil nutrients, organic carbon, soil nitrogen and particularly the labile P concentration.ConclusionsThe fungal community composition was likely affected by the alteration of vegetation cover in response to land use change, whereas the bacterial communities were mainly sensitive to changes in soil attributes. The study highlights the higher sensitivity of fungal communities than bacterial communities to land use changes.

Carbon and nitrogen contents and aggregation index of soil cultivated with onion for seven years using crop successions and rotations

Onion is usually cultivated using conventional tillage system (CTS), with excessive soil turning, leaving it with low or no vegetation cover. This favors erosive processes and impacts negatively diverse edaphic attributes. Adopting soil management systems with conservationist bases that use permanent soil coverage and crop rotation can maintain or improve these attributes (for example, soil aggregation and soil organic matter). The objective of this work was to evaluate the total organic carbon (TOC) and total nitrogen (TN) contents, aggregation index, and aggregate mass distribution of a Humic Cambisol cultivated with onions in succession or rotation with other species in no-tillage system (NTS) and CTS. The treatments were: maize/onion (NTS-T1); cover plants (winter)/onion (NTS-T2); maize/winter grasses/onion (NTS-T3); velvet bean/onion (NTS-T4); millet/cover plants (winter)/onion (NTS-T5); velvet bean/rye/onion (NTS-T6); maize/onion (CTS-T7); intercrops cover plants (summer)/onion (NTS-T8). Seven years after the implementation of the experiment, the weighted mean diameter (WMD) of the aggregates, distribution of macroaggregates, mesoaggregates, and microaggregates, and TOC, and TN contents of the soil (0–0.05, 0.05–0.10 and 0.10–0.20 m layers) were evaluated. Periodic soil turning (CTS) in the succession of maize, and onion (T7) reduces TOC and TN contents in the soil surface layer, compared to succession and rotation systems with onion crops in NTS. This negative effect on soil quality is connected to the reduction of aggregate stability, especially the decrease in the amount of macroaggregates. The use of grasses, especially winter grasses in rotation with maize (T3), preceding onion crops in NTS increases TOC content in the soil surface layer. Higher TN accumulation in the surface layer is found in areas with more soil cover plant species in rotation or succession with onion in NTS (T2, T3, T5, T6 and T8). The use of NTS for onion crops generates high soil aggregate stability, with predominance of macroaggregates, regardless of the crop succession or rotation system used. Treatments with no winter soil cover plants (T1, T4 and T7) reduce soil TOC contents and the mass of water-stable macroaggregates and increase the amount of microaggregates in the soil surface layer when compared to the other treatments.

Optimization of planting concrete materials with nitrogen and phosphorus removal characteristic

The adsorption performance of zeolite, steel slag and gravel on the nitrogen and phosphorus was studied in this paper, and the best aggregate of concrete with high efficiency and nitrogen removal was optimized; Through dynamic experiments to investigate the formation of white clover, Bermuda grass, Bahia grass and best aggregate combination planting concrete on the removal of ammonia nitrogen, total phosphorus, and optimized high efficiency removal of nitrogen and phosphorus removal of concrete. The result shows that in the ammonia nitrogen and total phosphorus concentration of 20mg/L and 5mg/L, the adsorption capacity of zeolite to ammonia nitrogen was significantly better than that of steel slag and gravel, while the difference between the three is not obvious, the zeolite is the best aggregate for the production of high efficiency nitrogen and phosphorus removal; In the influence of ammonia nitrogen and total phosphorus concentration keeping 5mg/L and 1mg/L, Bahia grass effect on zeolite plant growing concrete removal of nitrogen and phosphorus removal system promoting effect was significantly higher than that of Bermuda grass and white clover. Zeolite and Bahia combinations can be used as the best combination of plants to produce efficient nitrogen and phosphorus removal planting concrete aggregate.

Economic and Soil Environmental Benefits of Using Controlled‐Release Bulk Blending Urea in the North China Plain

AbstractCrop production must be increased in order to ensure a sustainable food supply for the growing world population. Controlled‐release urea (CRU) improves nutrient use efficiency and saves labor, but its use in crop production is limited due to its high cost. Bulk blending urea (BBU) consists of both CRU and conventional urea and could be an excellent substitute or replacement for CRU. Nevertheless, its economic benefits and soil environment impact are unknown. A 3‐year field experiment was conducted to investigate the effects of two different nitrogen management practices in terms of economic benefits, soil mineral nitrogen availability, aggregate stability, and soil microbial communities. Split applications of conventional urea (UREA) and a single application of BBU were tested on winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.) in the North China Plain between 2010 and 2013. Crop yields were measured after each harvest, and soil environmental parameters were determined after the 3‐year crop sequence. Relative to UREA, BBU significantly increased net revenue, soil inorganic nitrogen concentration, and the functional diversity of the soil microbial community without adverse effects on the soil bacterial community composition. On the other hand, BBU reduced the amount of soil macro‐aggregates and the mean weight diameter value of soil water‐stable aggregates. Although BBU showed great potential for improving wheat–maize cropping systems in the North China Plain, future studies should focus on optimizing the nitrogen dosage and the CRU ratio in BBU to decrease nitrogen leaching, avoid soil aggregate deterioration, and maintain crop yield. Copyright © 2017 John Wiley &amp; Sons, Ltd.

Chemical and hydrophysical attributes of an Oxisol under coffee intercropped with brachiaria in the Cerrado

Abstract The objective of this work was to evaluate the effect of irrigation and of the presence of brachiaria (Urochloa decumbens) between coffee (Coffea arabica) rows on coffee yield and on chemical and hydrophysical attributes of a Typic Haplustox. The study was conducted in the Cerrado region in Planaltina, Brasília, DF, Brazil, in a randomized complete block design, arranged in split-split plots, with four replicates. Water regimes (irrigated or rainfed) were assigned to the main plots, inter-row management systems to the subplots, and soil layers to the sub-subplots. The following soil attributes were determined: total organic carbon, total nitrogen, C/N ratio, carbon and nitrogen stocks, bulk density, aggregate stability, total porosity, macroporosity, low-retention microporosity, remaining microporosity, criptoporosity, and total and readily-available water, besides coffee yield. Irrigation of coffee plants, associated with brachiaria intercropped as a cover crop, increased coffee yield and favored chemical and hydrophysical soil attributes, improving soil structure and its ability to store water. Irrigation favors organic carbon stocks in the upper soil layers, whereas brachiaria favors soil physical attributes related to water availability to coffee.

Influence of humic acid applications on modulus of rupture, aggregate stability, electrical conductivity, carbon and nitrogen content of a crusting problem soil

Abstract. Soil structure is often said to be the key to soil productivity since a fertile soil, with desirable soil structure and adequate moisture supply, constitutes a productive soil. Soil structure influences soil water movement and retention, erosion, crusting, nutrient recycling, root penetration and crop yield. The objective of this work is to study humic acid (HA) application on some physical and chemical properties in weakly structured soils. The approach involved establishing a plot experiment in laboratory conditions. Different rates of HA (control, 0.5, 1, 2 and 4 %) were applied to soil during three incubation periods (21, 42 and 62 days). At the end of the each incubation period, the changes in physicochemical properties were measured. Generally, HA addition increased electrical conductivity values during all incubation periods. HA applications decreased soil modulus of rupture. Application of HA at the rate of 4 % significantly increased soil organic carbon contents. HA applications at the rate of 4 % significantly increased both mean soil total nitrogen content and aggregate stability after three incubation periods (p &lt; 0.05). Therefore, HA has the potential to improve the structure of soil in the short term.

Evaluation of soil quality for agricultural production using visible–near-infrared spectroscopy

Soil quality (SQ) assessment has numerous applications for agricultural management. Conventional quantification of SQ is based on laboratory analysis and integrative indices that can be costly and time consuming to obtain. A rapid, quantitative method using soil spectra, following the successful process of soil characterization by visible (VIS)–near infrared (NIR) spectroscopy, can provide a robust approach for soil monitoring. ObjectiveTo predict specific soil indicator properties and soil quality indices for the productive function of the soil using VIS–NIR spectroscopy, and to evaluate the suitability of spectral data for assessing and monitoring the impact of arable and grassland management in a temperate maritime climate. MethodsThe study used 40 sites in Ireland under both arable (n=20) and grassland (n=20) management systems. Specific indicators and soil quality indices (SQIs) identified by Askari and Holden (2014) and Askari (2014) were used as the reference standard for estimation using VIS–NIR spectra. Partial least-squares regression was used to predict the indicators and SQIs. SQI was predicted from both spectrally derived indicator values and directly from the soil spectra, and accuracy was assessed by comparison with laboratory and field derived measurements. ResultsThe indicators of SQ could be predicted with excellent (soil organic carbon and carbon to nitrogen ratio in grassland soils; total nitrogen, carbon to nitrogen ratio, extractable magnesium and aggregate size distribution in arable soils), good (bulk density of <2mm fraction in grassland soils) and moderate (penetration resistance, soil respiration and bulk density in arable soils) accuracy. The SQIs were predicted directly with excellent accuracy under grassland (RPD=3.04, R2=0.92, RMSE=0.03) and arable (RPD=2.78, R2=0.89, RMSE=0.04) management. Soil structural quality class, management type and management intensity were differentiable by their characteristic reflectance. ConclusionThe reliability of SQI and key indicators of soil quality, and the ability to differentiate by management practices and soil structural quality confirmed the efficiency of VIS–NIR spectroscopy for monitoring and evaluating SQ as a reliable alternative to conventional laboratory methods. PracticeSpectroscopy has the potential to provide a reliable approach that will allow rapid, low cost, high frequency SQ monitoring for multiple purposes, and can play an important role in sustainable land management. ImplicationsVIS–NIR spectroscopy was shown to be suitable for quantitative assessment of soil quality, thus paving the way for development of an applied tool that can be used for agricultural management on the context of soil security, soil health, soil protection and soil quality.

Ozone pollution influences soil carbon and nitrogen sequestration and aggregate composition in paddy soils

Background and aims Much attention has focused on the effects of tropospheric ozone (O3) on terrestrial ecosystems and plant growth. Since O3 pollution is currently an issue in China and many parts of the world, understanding the effects of elevated O3 on soil carbon (C) and nitrogen (N) sequestration is essential for efforts to predict C and N cycles in terrestrial ecosystems under predicted increases in O3. Thus the main objective of this study was to determine whether an increases in atmospheric O3 concentration influenced soil organic C (SOC) and N sequestration.

GLOMALIN, CARBON, NITROGEN AND SOIL AGGREGATE STABILITY AS AFFECTED BY LAND USE CHANGES IN THE HUMID FOREST ZONE IN SOUTH CAMEROON

Arbuscular mycorhizal fungi (AMF) produce a glycoprotein (glomalin) important for soil structure, fertility and therefore plant nutrition which can be used to evaluate the impact of agricul tural practices on soil quality across many land use syst ems. In the present study, its influence was invest igated on soil fertility and aggregation in 3 different la nd use systems of the humid forest zone of southern Cameroon. Soils were sampled at 10 cm depth from 03 native forest, 03 fallow and 03 continuous growing fields systems at Metet (South Cameroon) for the determination of easily extractable glomalin (EEG), total glomalin (TG), carbon (C), nitrogen (N ) and soil water stable aggregate of 1-2 mm diamete r (WSA 1-2mm ). Results showed that both EEG and TG concentrations significantly decreased (P < 0.01) from the forest to the growing field, via the fallo w system. The rate of EEG decrease was 29.82 % and 38.35 % in the fallow and the growing field system compared to the forest system, respectively. For TG , the decrease rate was 16.65 % to 46.04 % for the fa llow and the growing field system compare to the forest system respectively; while C, N, and organic matter (OM) did not changed significantly. The proportion of C, N and OM were 93.6 %, 88.3 %, 93.7 % for the growing field system compared to the forest system respectively. The WSA 1-2mm decreased from the forest to fallow and growing fi eld systems, with respective rates of 19.69% and 32.81 %. There was high positive correlation between C, N and EEG (r 2 = 0.76, 0.55; P < 0.01), suggesting the possible im plication of glomalin to soil stock of C and N.

Glomalin related soil protein, carbon, nitrogen and soil aggregate stability as affected by land use variation in the humid forest zone of south Cameroon

Arbuscular mycorhizal fungi (AMF) produce a glycoprotein (glomalin) which play an important role in the maintenance of soil structure and fertility. On the other hand, it can be used to evaluate the impact of agricultural practices on soil quality across many land use systems. We assessed land use impact on glomalin related soil proteins (GRSPs), soil quality and aggregation in the humid forest zone in southern Cameroon. Forest, short fallow and field crop production soil samples were used to determine GRSPs, carbon (C), nitrogen (N) and water stable aggregate (WSA1–2mm). Results showed that GRSPs significantly decreased from the forest to fallow and the field crop production systems. The easily extractable GRSP (EEGRSP) was 30% and 39% less under fallow and field crop production respectively, relative to the forest soils. Similarly, total GRSP (TGRSP) was 17% and 46% less under fallow and field crop production respectively, relative to the forest soils. C, N, and organic matter (OM) did not change significantly within the land use systems. The WSA1–2mm was 20% less under fallow, and 33% less under field crop production relative to the forest system. However, AMF spores augmented from forest to fallow and field crop production system. There was a positive correlation between GRSPs (EEGRSP, TGRSP) and AM fungal spore density suggesting the possible implication of these fungi to the production of the GRSP in this zone. There was also a positive correlation between C, N and EEGRSP, suggesting the implication of GRSP in stocking soil C and N in this zone. Likewise, a positive correlation between OM and TGRSP was found meaning the implication of GRSPs to OM pools in the soil of this zone. WSA1–2mm was also correlated with TGRSP, C and OM, suggesting the possible coactions of GRSP, OM to the formation of WSA1–2mm, and thereby promoting the build up of soil structure. These results highlight the view that GRSP can be used as an indicator of soil quality in this region and should be considered as a criteria when define agricultural management strategies. AM fungal and GRSP might be useful to monitor soil degradation in this zone.

Soil Fertility Indices of Citrus Orchard Land Along Topographic Gradients in the Three Gorges Area of China

In the Three Gorges Area of China, soil erosion and the resultant non-point source pollution and ecological degradation have endangered agricultural ecosystems and fresh water reservoirs. Although efforts have been undertaken to reduce soil and water losses from slope land used for citrus production, information on the effects of management practices on soil fertility indices is either limited or nonexistent. This study was conducted to compare the effects of 10 years of various management practices, citrus intercropped with white clover (WC), citrus mulched with straw (SM), citrus intercropped with contour hedgerows (CH), citrus orchard land with impermeable membrane (IM), and citrus intercropped with wheat ( Triticum aestivum) and peanut ( Arachris hypogaea) (WP), as treatments on soil fertility indices with that of the conventional citrus management (CM). Results showed that the soil organic carbon, total and available nitrogen, available potassium, and water-stable aggregate (> 0.25 mm) contents at the 0–5 cm depth were higher for the WC and SM treatments than the CM treatment. There was also spatial variation in soil fertility along slopes of the WC and SM treatments. The soil total and available nitrogen, phosphorus, and potassium, and water-stable aggregate (> 0.25 mm) contents at both the 0–5 and 5–20 cm depths were higher for the CH and IM treatments than the CM treatment. The average soil available nitrogen and available potassium contents were higher for the WP treatment than the CM treatment, but the WP treatment had little effect on the soil organic carbon, total nitrogen, and water-stable aggregate (> 0.25 mm) contents. These suggested that white clover intercropping and straw mulching were the most effective approaches to improve soil fertility in citrus orchard land of the Three Gorges area.

The modes of the one phonon infrared absorption spectra of nitrogen aggregate defects in diamond

The mid-IR absorption spectra of various nitrogen aggregate defects in diamond are calculated, starting from the vibrational density of states, and compared to the experimental spectrum of these defects. The single substitutional 1344 cm −1 peak is a local mode transforming as E, and does not shift with 15N isotopic substitution. The absorption spectra of the C and the A centres are the sum of a mode transforming as A 1 and E at a C 3v and D 3d symmetrical defect respectively. The absorption spectrum of the B defect is due to the interaction with modes transforming as T 2 at a T d defect. The maxima at 1095 cm −1 appearing in the absorption spectra of all types of nitrogen aggregates is completely determined by the total mass, the symmetry and the position of the various maxima in the vibrational density of states.

Measuring and decomposing changes in agricultural productivity, nitrogen use efficiency and cumulative exergy efficiency: Application to OECD agriculture

This paper uses an aggregate quantity space to decompose the temporal changes in nitrogen use efficiency and cumulative exergy use efficiency into changes of Moorsteen–Bjurek (MB) Total Factor Productivity (TFP) changes and changes in the aggregate nitrogen and cumulative exergy contents. Changes in productivity can be broken into technical change and changes in various efficiency measures such as technical efficiency, scale efficiency and residual mix efficiency. Changes in the aggregate nitrogen and cumulative exergy contents can be driven by changes in the quality of inputs and outputs and changes in the mixes of inputs and outputs. Also with cumulative exergy content analysis, changes in the efficiency in input production can increase or decrease the cumulative exergy transformity of agricultural production. The empirical study in 30 member countries of the Organisation for Economic Co-operation Development from 1990 to 2003 yielded some important findings. The production technology progressed but there were reductions in technical efficiency, scale efficiency and residual mix efficiency levels. This result suggests that the production frontier had shifted up but there existed lags in the responses of member countries to the technological change. Given TFP growth, improvements in nutrient use efficiency and cumulative exergy use efficiency were counteracted by reductions in the changes of the aggregate nitrogen contents ratio and aggregate cumulative exergy contents ratio. The empirical results also confirmed that different combinations of inputs and outputs as well as the quality of inputs and outputs could have more influence on the growth of nutrient and cumulative exergy use efficiency than factors that had driven productivity change.

Density functional studies of muonium in nitrogen aggregate containing diamond: theMuX centre

Diamond has potential as a wide band-gap semiconductor with high intrinsic carrier mobility,thermal conductivity and hardness. Hydrogen is involved in electrically active defects inchemical vapour deposited diamond, and muonium, via muon spin spectroscopy, canprovide useful characterization for the configurations adopted by H atoms in a crystallinematerial. We present the results of a computational investigation into the structure of theMuX centre proposed to be associated with nitrogen aggregates. We find that the propensity ofhydrogen or muonium to chemically react with the lattice makes the correlation ofMuX with nitrogen aggregates problematic, and suggest alternative structures.

Long term effects of fertilization on carbon and nitrogen sequestration and aggregate associated carbon and nitrogen in the Indian sub-Himalayas

An understanding of the dynamics of soil organic carbon (SOC) as affected by farming practices is imperative for maintaining soil productivity and also for restraining global warming by CO2 evolution. Results of a long-term (30 year) experiment in the Indian Himalayas under rainfed soybean (Glycine max L.)—wheat (Triticum aestivum L.) rotation was analyzed to determine the influence of mineral fertilizer and farmyard manure (FYM) application at 10 Mg ha−1 on SOC and total soil nitrogen (TSN) stocks and distribution within different aggregate size fractions. Fertilizers (NP, NK and NPK) and FYM in combination with N or NPK were applied before the soybean crop every year and no nutrient was applied before the wheat crop. Results showed that addition of FYM with N or NPK fertilizers increased SOC and TSN contents. The overall gain in SOC in the 0- to 45-cm soil depth interval in the plots under NPK + FYM treatment over NPK was 17.18 Mg C ha−1 in 30 year. The rate of conversion of input C to SOC was about 19% of each additional Mg C input per hectare. SOC content in large size aggregates was greater than in smaller size aggregates, and declined with decreased aggregate size. Thus, long-term soybean–wheat rotation in a sandy loam soil of the Indian Himalayas sequestered carbon and nitrogen. Soil organic C and TSN sequestration in the 0.25- to 0.1-mm size fraction is an ideal indicator of long-term C and N sequestration, since this fraction retained maximum SOC/TSN stock.

Influence of olive oil solid waste applications on soil pH, electrical conductivity, soil nitrogen transformations, carbon content and aggregate stability

Some of the agricultural wastes have important economic potentials to be used as a plant nutrition and/or soil conditioner. Olive oil solid waste (OSW) is one of them. The aim of this study was to determine effects of OSW on soil pH, electrical conductivity (EC), improving soil nitrogen (N) status, soil aggregate stability and soil carbon contents. Different rates of OSW (control, 2%, 4% and 8%, w/w) were applied to coarse soils and incubated for 2 months. OSW applications decreased soil pH values. The mean EC value of soil measured 2 months after the incubation was greater than that of the first month. Application of OSW at the rate of 8% has significantly increased soil total organic nitrogen contents. OSW applications at the rate of 8% (w/w) significantly increased both mean SOC content (3.5%) and aggregate stability (88%) after 2 months of incubation ( p < 0.01). Therefore, OSW has great potential to improve soil structure of coarse textured soil in short term.

Optical modulation of bulk one-phonon state in diamond

Infrared absorption and electron spin resonance measurements have been performed in nitrogen-containing mixed-type diamonds under several illumination conditions. It has been observed that bulk one-phonon absorption spectra are modulated by illumination of higher than 2.0 eV in photon energy and the change recovers within a few hours after the excitation light is turned off. The results are explained by the change in the charge state of isolated nitrogen, and a characteristic absorption band created by the positive charge state of isolated nitrogen (N+) is proposed. This phenomenon is applicable in decomposing the infrared absorption spectra of diamonds into each component, which contain information about the type and concentration of nitrogen aggregate.

Infrared absorption by the B nitrogen aggregate in diamond

Abstract Two approaches have been adopted in attempting to determine the strength of the one-phonon infrared absorption by the B nitrogen aggregate in diamond. On the one hand, we have heat treated purely type IaA specimens with known infrared absorption strengths (and thus also known nitrogen concentrations) to bring about partial aggregation of the A centres to B centres, monitoring changes in the strengths of the A, and resultant B, one-phonon components by decomposition of the ensuing infrared spectra. Secondly, we have made direct chemical assays of nitrogen in diamonds that show dominant B absorption features. This approach is complicated because diamonds in which the B aggregate is the only point defect also contain extended defects that may or may not involve nitrogen. These defects may or may not, in turn, contribute to absorption in the one-phonon region. Nevertheless, the nitrogen concentrations have been measured for two distinct groups of diamonds that both uncritically might at first glance ...