Faster Decomposition Rates Research Articles

Mechanism of low temperature decomposition of NiO single crystals

The decomposition of NiO single crystal was investigated under dissociative conditions in the temperature interval between 330 and 850 °C in the absence of reducing gas species. An unusually fast and constant decomposition rate was measured at the lowest temperatures, coupled with an unusual largely porous microstructure of the metallic product layer. This anomalous high reaction rate was interpreted on the basis of a decomposition mechanism implying the dissociative vaporization of the oxide followed by the condensation of the metal. The proposed mechanism is supported by the microstructure of the product and of the reacting interface. The complex dependence of reaction rate from temperature was shown to be related to a collapse of the porous product to form a compact metal layer at higher temperatures due to sintering.

Rapid decomposition of maize detritus in agricultural headwater streams

Headwater streams draining agricultural landscapes receive maize leaves (Zea mays L.) via wind and surface runoff, yet the contribution of maize detritus to organic-matter processing in agricultural streams is largely unknown. We quantified decomposition and microbial respiration rates on conventional (non-Bt) and genetically engineered (Bt) maize in three low-order agricultural streams in northwestern Indiana, USA. We also examined how substrate quality and in-stream nutrient concentrations influenced microbial respiration on maize by comparing respiration on maize and red maple leaves (Acer rubrum) in three nutrient-rich agricultural streams and three low-nutrient forested streams. We found significantly higher rates of microbial respiration on maize vs. red maple leaves and higher rates in agricultural vs. forested streams. Thus both the elevated nutrient status of agricultural streams and the lability of maize detritus (e.g., low carbon-to-nitrogen ratio and low lignin content) result in a rapid incorporation of maize leaves into the aquatic microbial food web. We found that Bt maize had a faster decomposition rate than non-Bt maize, while microbial respiration rates did not differ between Bt and non-Bt maize. Decomposition rates were not negatively affected by genetic engineering, perhaps because the Bt toxin does not adversely affect the aquatic microbial assemblage involved in maize decomposition. Additionally, shredding caddisflies, which are known to have suppressed growth rates when fed Bt maize, were depauperate in these agricultural streams, and likely did not play a major role in maize decomposition. Overall, the conversion of native vegetation to row-crop agriculture appears to have altered the quantity, quality, and predictability of allochthonous carbon inputs to headwater streams, with unexplored effects on stream ecosystem structure and function.

Preservation of broadleaf species in Korean pine (Pinus koraiensis) plantations affects soil properties, carbon storage, biomass allocation, and available nitrogen storage

We analyzed forest floor mass, soil properties, soil organic carbon (SOC) storage, soil available nitrogen (NO3–-N and NH4+-N) (SAN) storage, litter production and decomposition, tree biomass, and the growth rate of Korean pine ( Pinus koraiensis Sieb. et Zucc.) to determine the impacts of keeping broadleaf species in the Korean pine plantation on Korean pine growth and identify the interactions of plants and soil. Forest biomass and litter production were significantly higher in the broadleaf mixed Korean pine plantation (KBP) than in the pure Korean pine plantation (KP). Broadleaf species redistributed carbon from forest floor to mineral soil via its fast litter decomposition rate with the result of a smaller forest floor mass and a greater SOC storage in KBP than in KP. KBP had significantly higher SOC and SAN storages, SOC and SAN concentrations, and pH, and lower soil bulk density than KP. Such differences can be largely explained by the input of broadleaf litter into KBP. The Korean pine in KBP had a greater growth rate and allocated a smaller proportion of biomass below ground, indicating that the broadleaf species influenced the Korean pine growth and biomass allocation pattern by changing soil properties. There was a positive feedback among litter N release rate, SAN storage, and plant growth rates.

Leaf litter decomposition of dominant tree species of Namdapha National Park, Arunachal Pradesh, northeast India

Rates of weight loss and nutrient (N and P) release patterns were studied in the leaf litter of the dominant tree species (Ailanthus grandis, Altingia excelsa, Castanopsis indica, Duabanga sonneriatioides, Dysoxylum binectariferum, Mesua ferrea, Shorea assamica, Taluma hodgsonii, Terminalia myriocarpa and Vatica lancefolia) of a tropical wet evergreen forest of northeast India. Nitrogen and phosphorus mineralization rate and decay pattern varied significantly from species to species. In general, the decay pattern, characterized by using a composite polynomial regression equation, exhibited three distinct phases of decay during litter decomposition—an initial slow decay phase (0.063% weight loss day−1), followed by a rapid decay phase (0.494% weight loss day−1) and a final slow decay phase (0.136% weight loss day−1). The initial chemical composition of the litter affected decomposition rates and patterns. Species like D. sonneriatoides, D. binectariferum, and T. hodgsonii with higher N and P content, lower carbon and lignin content, and lower C:N ratio and lignin:N ratio exhibited relatively faster decomposition rates than the other species, for example M. ferrea, C. indica and A. grandis. A slow decay rate was recorded for species such as M. ferrea, C. indica, and A. grandis. The initial N and P content of litter showed significant positive correlations with decay rates. Carbon and lignin content, lignin:N, and C:N showed significant negative correlations with decay rates. Soil total N and P, and rainfall, soil temperature, and soil moisture had positive correlations with decay rates. The rapid decomposition rates observed in comparison with other different forest litter decay rates confirm that tropical wet evergreen forest species are characterized by faster decomposition rates, indicating a faster rate of organic matter turnover and rapid nutrient cycling.

Properties of a Nano CaO/Al2O3 CO2 Sorbent

This project studied the properties of nano CaO/Al2O3 as a high-temperature CO2 sorbent for its use in an adsorption enhanced reforming reaction. The sorbent containing nano CaCO3 precursors and aluminum oxide was prepared, and evaluation of the CO2 adsorption properties by a thermogravimetric analyzer, the results show that nano CaO/Al2O3 has a faster decomposition rate and has a higher CO2 adsorption ratio than micro CaO/Al2O3. The maximum adsorption ratio occurs at temperatures of 650 °C under a CO2 partial pressure of 0.33 atm. Durability studies show that the CO2 adsorption ratio remains at 68.3% after 50 cyclic runs under a carbonation temperature of 650 °C and calcination temperature of 800 °C, respectively. XRD, SEM, and BET were used for studying the change of micro characteristics of the CO2 sorbents before and after multiple carbonation−calcination runs. The results showed that the pore size of CaO/Al2O3 sorbents was enlarged and that a new substance (Ca12Al14O33) was formed even under a temperature of 800 °C for the function of keeping the compound stable and durable.

INFLUENCE OF DIFFERENT FOOD SOURCES ON GROWTH AND REPRODUCTION PERFORMANCE OF COMPOSTING EPIGEICS: EUDRILUS EUGENIAE, PERIONYX EXCAVATUS AND PERIONYX SANSIBARICUS

The impact of organic material quality on biomass production and reproduction potential of commercial composting earthworm species: Eudrilus eugeniae, Perionyx excavatus and Perionyx sansibaricus were studied, by using three different type of culture material namely Jbs: (Jowar straw (Sorghum vulgare ) + bajra straw ( Pennisetum typhoides ) + sheep manure) (1:1:2), fym (farmyard manure), and Kw + Ll (Kitchen waste + leaf litter of Magifera indica ) (1:1), under laboratory conditions for 150 days. The above substrate or culture materials have different palatability, particle size and physio- chemical composition. Kitchen waste (C-to-N = 26.7) as well as farmyard manure (C-to-N = 27.4) is a high quality material with fast decomposition rates, while crop residues are low quality materials with slow decomposition rates (C-to-N = 45.6). All the three studied earthworm species showed maximum biomass production rate in Kw + Ll culture ( E. eugeniae = 9.80 ± 0.01 mg worm -1 day -1 , P. excavatus = 3.75 ± 0.01 mg worm -1 day -1 , and P. sansibaricus = 3.77 mg worm -1 day -1 ). Individual cocoon production rate varied drastically, and maximum value (worm -1 week -1 ) of it was observed in Kw + Ll for E. eugeniae (1.88 ± 0.15) and P. sansibaricus (1.77 ± 0.14), while P. excavatus showed maximum cocoon production rate in Fym (1.79 ± 0.17). The hatchling success of cocoons obtained from different beddings was also observed and cocoon obtained from Kw + Ll culture exhibited maximum hatchling success (%) in all the three species studied. The cocoons of both E. eugeniae and P. sansibaricus , obtained from Fym culture showed the highest number of hatchlings (cocoon -1 ) i.e. 1.59 ± 0.04 and 1.81 ± 0.10, respectively, whereas cocoons of P. excavatus showed the highest hatchling number (1.77 ± 0.06) in Kw + Ll. In this present study, there was a consistent trend of decreasing individual biomass as well as cocoon production rate, followed by their peak values with ageing of the culture materials. The relationship between different earthworm parameters and N-content or C-to-N of culture material was also evaluated. The biomass production rate and hatching success in all the three species studied showed direct correlation (p<0.05) with N-content of the culture material. However, beddings' N-content did not affect the individual cocoon production rate, except to P. sansibaricus (r = 0.987, P<0.001). The number of hatchlings per cocoon for P. sansibaricus, showed good correlation (r = 0.935 p<0.01) with N-content of organic material used for worm culture. Results clearly show a possible relation between hatchling success/number of hatchlings per cocoon, and chemistry of culture substrate.

Kinetics of Decomposition of Un‐conventional Farm‐Based Crop Residues and Their Composting and Quality Monitoring

Castor and sunflower, drought‐tolerant crops, are cultivated in the semi‐arid tropics of the world. The nutrient‐rich residues of these crops are mostly burnt because of their high C/N (C/N)‐ratios. These high C/N‐ratio residues can be composted and recycled successfully, if they are supplemented with other low C/N‐ratio farm‐based organics and some chemical additives. To study the rate kinetics and half‐life of decomposition of castor (C/N ratio: 75∶90) and sunflower (C/N ratio 57∶47) residue mixtures and the manure value of the compost thus prepared, two on‐farm experiments were conducted at Hayathnagar Research Farm (17° 18′ N latitude, 78° 36′ E longitude, and an elevation of 515 m above sea level) of Central Research Institute for Dryland Agriculture, Hyderabad, India. The decay rate constants obtained on the basis of the exponential functions using the data on weight loss, C concentration, and C/N ratios indicated that among the four combinations of treatments, castor stalks+gliricidia loppings+cattle dung had the fastest rate of decomposition with an average rate constant value of 0.0043 day−1. To achieve 50% decomposition (half‐life), the time periods computed for castor stalks+gliricidia loppings+cattle dung and sunflower stalks+gliricidia loppings+cattle were 197 and 278 days, respectively. On an average basis, sunflower‐based manure contained a significantly higher amount of total N (14.6 gm kg−1) than castor‐based manures (12.2 gm kg−1). The corresponding total hydrolyzable N values were 8.2 and 8.15 gm kg−1, respectively. Amino acid N was found to be the predominant constituent of the total acid hydrolyzable N in the manure. Use of earthworms in composting enriched the manure in terms of mineral [nitrate (NO3)+ammonium (NH4)‐N] and hexosamine‐N fractions. The full article deals with the decomposition patterns (periodical changes in weight loss, C concentration and C/N ratios), decay‐prediction functions, composting, and manure quality of the castor‐ and sunflower‐based residue mixtures.

Indirect effects of precipitation variation on the decomposition process of Mongolian oak (Quercus mongolica) leaf litter

The effect of precipitation variation on the chemistry of Mongolian oak (Quercus mongolica) leaf litters was examined by analyzing litters of Mongolia oak saplings under four precipitation gradients. The decomposing process of these leaf litters in the Mongolian oak dominated forest was assessed using litter bag method. Compared with the litters of the Mongolian oak saplings from the natural precipitation site (A), litters produced by Mongolian oak from the driest precipitation gradient (A450) had significantly higher concentrations of nitrogen (N), phosphorus (P) and potassium (K) while lower acid-insoluble fraction (AIF) concentration. The decomposition study showed that A450 exhibited significantly higher decomposition rate, mineralization rates of N, P and K as well as much shorter N and P net immobilization periods. On the contrary, litters produced by seedlings from wettest gradient (A850) showed a totally opposite pattern. Litters from saplings that received comparable precipitation (A650) to those at the natural site (A) had significantly higher N concentration and faster decomposition rate as well as release rates of N, P and K. The mass loss patterns for the four litter types fitted the exponential model and the decay constant (k) can be well predicted by initial AIF/N. During the decomposition period, N concentration was best related to the percentage of mass remaining of the litters with relatively higher AIF concentrations and lower N concentrations, but the percentage of mass remaining of litters with lower AIF concentrations and higher N concentrations correlates strongly with AIF con centration. Our study proved that changes in precipitation significantly altered the litter quality, and therefore indirectly changed the decay process of leaf litters.

Photophysics and Photochemical Studies of 1,4-Dihydropyridine Derivatives

The absorption and fluorescence properties of nifedipine (NPDHP), felodipine (CPDHP) and a series of structurally related 1,4-dihydropyridines were studied in aqueous solution and organic solvents of different properties. The absorption and fluorescence spectra were found to depend on the chemical nature of the substituents at the position 4 of the 1,4-dihydropyridine ring (DHP) and on solvent properties. In aqueous solution, the fluorescence spectra of 4-phenyl substituted compounds are blue-shifted with respect to the alkyl substituted compounds. The more fluorescent compound is CPDHP. Nifedipine is not fluorescent. All compounds, with the exception of CPDHP, present monoexponential fluorescence decay with very short lifetime (0.2-0.4 ns). CPDHP showed a biexponential emission decay with a long-lived component of 1.7 ns; this behavior is explained in terms of different conformers because of the hindered rotation of the phenyl group by the ortho-substitution. Analysis of the solvent effect on the maximum of the absorption spectrum by using the linear solvent-energy relation solvato-chromic equation indicates the redshifts are influenced by the polarizability, hydrogen bonding ability and the hydrogen bond acceptance of the solvent. Whereas, the fluorescence characteristics (spectra, quantum yields and lifetimes) are sensitive to the polarizabilty and hydrogen bond ability of the solvents. Photo-decomposition of nifedipine is dependent on the solvent properties. Faster decomposition rates were obtained in nonprotic solvents. The 4-carboxylic derivative goes to decarboxylation. Under similar conditions, the other DHP compounds did not show appreciable photodecomposition.

Decay progression and classification in two old-growth forests in Atlantic Canada

This paper investigates the relationship between visually apparent stage of decay of coarse woody debris (CWD) and time since death of decaying balsam fir ( Abies balsamea L.) and black spruce ( Picea mariana [P. Mill]) in old-growth forests in western Newfoundland and in the Cape Breton Highlands (CBH) of Nova Scotia. These sites are two of the least disturbed old-growth forest locations remaining in Atlantic Canada. In Newfoundland, a total of 42 detrital samples were collected from downed logs and standing snags, of which 36 had their mortality dates determined. In the CBH, 50 detrital samples were collected, of which death dates for 44 samples were obtained. For both sites, samples represented all visually discernable classes of decay. In Newfoundland, these visual decay classes were separated by approximately 17 years for a minimum decay time of 85 years. In CBH, a faster rate of decomposition was apparent, with 12-year classes and a minimum decay time of logs of 60 years. Evidence points toward a climate-driven decay regime in both locations, with the longer time frame evident in Newfoundland thought to result from lower temperatures and fewer snow-free days than in CBH.

Role of physical fragmentation and invertebrate activity in the breakdown rate of leaves

We evaluated the relative importance of current velocity and invertebrate activities in the breakdown rate of alder (Alnus glutinosa (L.) Gaertner) leaves. Decomposition experiments were carried out in artificial channels, where current velo- city and shredder presence were manipulated, and in a 4 th order stream, in both summer and autumn, where litter bags were incubated in several reaches differing in both depth and current velocity. Alder leaves incubated in artificial channels decomposed signifi- cantly faster in the presence of shredders than in their absence (k = 0.0368/d vs. k = 0.0210/d in low current and k = 0.0472/d vs. k = 0.0219/d in high current). However, cur- rent (up to 2.35 m/s) had no significant effect on decomposition rates. In channels with- out invertebrates, no significant differences in k values were found between coarse and fine mesh bags in high (0.20 m/s) and low (0.05 m/s) current. Leaves incubated in the stream during summer, in reaches with current velocity ranging from 0.003 to 1.185 m/s, did not differ in their decomposition rates (k = 0.0489/d to k = 0.0645/d). In autumn, leaves exposed to high current (1.228 m/s) had faster decomposition rate (k = 0.0417/d vs. k = 0.0136/d), which may be related to sediment transport during this time of the year or to the tendency for higher number of shredders in high current-shallow reaches.

Litterfall and Decomposition of Rhizophora mangle L. in a Coastal Lagoon in the Southern Gulf of Mexico

The dynamics of Rhizophora mangle litter production and decomposition were studied in a tropical coastal lagoon on the Gulf of Mexico in Veracruz, Mexico over a year (October 2002–October 2003). This region is characterized by three seasons: northerly winds (called ‘nortes’), dry, and rainy. Annual litter production (1116 g m−2) followed a seasonal pattern with leaf litter as the main fraction (70%) with two peaks in the dry and one in the rainy season. Leaf decomposition was evaluated with two types of litter bag in each season: fine mesh (1×1 mm) and coarse mesh (3×7 mm). Decomposition data were adjusted to a single negative exponential model. The results indicated faster decomposition rates in the coarse litter bag and significant differences among seasons. However these differences occurred after the 60th day of decomposition, indicating that leaching and microbial action were responsible for more than 50% of mass loss. After this period, the effects of aquatic invertebrates were evident but depended on climatic conditions. In the rainy season, the gastropod Neritina reclivata was associated with increasing leaf decomposition rate. In the ‘nortes’ season, the effect of aquatic invertebrates was smaller, and there were no differences in the decay constants calculated for the two litter bag types. High litter production represents an important input of organic matter which, through decomposition, may represent an important source of C, N, and P in this aquatic system.

Photophysics and Photochemistry of Nalidixic Acid†

The photophysics and photochemistry of nalidixic acid (NA) were studied as function of pH and solvent properties. The ground state of NA exhibits different protonated forms in the range of pH 1.8-10.0. Fluorescence studies showed that the same species exist at the lowest singlet excited state. Absorption experiments were carried out with NA and with the methylated analog of nalidixic acid (MNE) in different organic solvents and water pH 3, where the main species corresponds to that protonated at the carboxylic group. These studies and the DFT calculation of torsional potential energy profiles suggest that the most stable conformation of the NA in nonprotic solvents corresponds to a closed structure caused by the existence of intramolecular hydrogen bond. Absorption and fluorescence spectra were studied in sulfuric acid solution. The pK value (Ho -1.0) found in these conditions was attributed to the protonation of the 4' keto oxygen atom of the heterocyclic ring. Theoretical calculations (DFT/B3LYP/6-311G*) of the energies of the different monoprotonated forms of the NA and Fukui indexes (f(x)-) showed that the species with the proton attached to 4' keto oxygen atom is the most stable of all the cationic forms. MNE and enoxacin also showed the protonation of the 4' keto oxygen atom with similar pK values. The photodecomposition of NA is dependent on the medium properties. Faster decomposition rates were obtained in strong acid solution. In nonprotic solvents, a very slow decomposition rate was observed.

Nonparasitic Nematoda provide evidence for a linear response of functionally important soil biota to increasing livestock density

Soil acidity, nutrient availability and livestock density have a major influence on the belowground ecological community. As fast decomposition rates are due mostly to bacterial-based pathways and slower decomposition rates mostly to fungal-based pathways, it is helpful to condense empirical information in the so-called Nematode Channel Ratio (NCR). The NCR is shown to be a good indicator of efficiency in soil decomposition processes. We argue that in intensive agroecosystems, other fungivore members of the decomposer food web may outcompete the hyphal-feeding nematodes. We demonstrate how the NCR can be used to set ecological standards for sustainable use of the soil in agroecosystems. To summarize the interactions between the microbial resources and the decomposer nematofauna according to increasing land management, we propose the use of the fifth percentile as proxy for a sustainable environmental quality of grasslands on sandy soils, and the NCR mean as the upper threshold for low-stocked farms.

Litter quality and nutrient cycling affected by grazing‐induced species replacements along a precipitation gradient

One of the potential mechanisms for the impact of herbivores on nutrient cycling is the effect of selective grazing on litter quality through changes in species composition. However, the scarce evidence collected on this mechanism is controversial and seemingly influenced by site‐specific variables. In this paper, we explored the consequences of grazing‐induced changes in species composition on litter quality and nitrogen cycling with a regional perspective. Along a 900‐mm of mean annual rainfall gradient, we selected species promoted and diminished by grazing from three natural rangelands of Argentina, analyzed their litter quality, and determined their decomposition and nutrient release kinetics under common greenhouse conditions. Litter quality and decomposition rates were strongly associated with plant response to grazing. However, the magnitude and direction of these differences depended on the ecosystem considered. In the wettest site, the species promoted by grazing (forbs) had higher nitrogen and phosphorus contents, faster decomposition rates, and higher release of nitrogen to the soil than species diminished by grazing (C3 and C4 grasses). In the intermediate and dry sites, species promoted by grazing had lower nitrogen and phosphorus contents, and slower decomposition rates than those diminished by grazing (C3 grasses in both cases). Decomposition of the entire group of species was not correlated with mean annual rainfall, but when litter of the species diminished by grazing was analyzed, it was negatively correlated with precipitation. Nitrogen was immobilized more often than mineralized, even after one year of incubation. Immobilization was negatively correlated with precipitation. All these results indicate that grazing may significantly alter nutrient cycling by affecting litter quality through changes in species composition. These effects seem to be larger when species replacements induced by grazing either involve functional groups, as it was the case in our wettest site, or change root to shoot ratios. Therefore, the functional groups involved in the replacement of species as well as shifts between belowground and aboveground allocation should play a key role in grazing‐induced changes on nitrogen cycling.

Effects of Carrot Powder in Dough on the Lipid Oxidation and Carotene Content of Fried Dough during Storage in the Dark

ABSTRACT: Lipid oxidation and carotene content changes in fried dough containing carrot powder during storage at 60°C in the dark were studied. Flour dough containing carrot powder at 0%, 10%, 20%, or 30% was fried in 160°C soybean oil and stored in a 60°C incubator in the dark for 12 d. As storage time of the fried dough increased, conjugated dienoic acids and β‐anisidine values of the fried dough increased. Addition of carrot to the dough lowered CDA and PAV of fried dough during storage and improved the lipid oxidative stability of the fried dough in the dark. Carotenes in the fried dough containing carrot powder were decomposed during storage, and faster decomposition rate was found in the dough containing less carrot powder.

Spark plasma sintering (SPS) consolidated ceramic composites from plasma-sprayed metastable Al2TiO5 powder and nano-Al2O3, TiO2, and MgO powders

Abstract Spark plasma sintering (SPS) was applied to consolidate the nano-Al 2 O 3 , TiO 2 , MgO powders and plasma-sprayed metastable Al 2 TiO 5 powder. The fully dense ceramics had been prepared successfully. It was found that the starting nano-Al 2 O 3 reacted with nano-TiO 2 powder to form the Al 2 TiO 5 phase after SPS consolidation at 1150 °C under a pressure of 63 MPa. The starting plasma-sprayed Al 2 TiO 5 was stable above 1150 °C after SPS under 63 MPa, though in oxidizing atmospheres under the ambient air pressure, the stable temperature range of Al 2 TiO 5 was above 1280 °C. There was a fast decomposition rate for plasma-sprayed Al 2 TiO 5 at 1000 °C during SPS, whereas in oxidizing atmospheres under the ambient air pressure at 1000 °C its decomposition is very slow. The microstructure of powder, applied pressure, and/or SPS characteristics, etc. obviously had an effect on the stable temperature and/or decomposition rate of Al 2 TiO 5 . The addition of MgO advanced the formation of Mg 0.3 Al 1.4 Ti 1.3 O 5 along with MgAl 2 O 4 in the ceramics prepared both from plasma-sprayed powder and from nano-powder. In comparison with the composition of the ceramics without MgO additive, α-Al 2 O 3 , TiO 2 , and Al 2 TiO 5 , the ceramics with MgO additive consisted of only two phases, Mg 0.3 Al 1.4 Ti 1.3 O 5 and MgAl 2 O 4 spinel. The small equiaxed MgAl 2 O 4 spinel grains were distributed in a matrix of Mg 0.3 Al 1.4 Ti 1.3 O 5 with a large grain size.

Decomposition of leguminous crop residues in a ‘jhum’ cultivation system in Arunachal Pradesh, India

AbstractDecomposition of leaves, stems, and roots of two leguminous plants, french bean and pea, was studied in a ‘jhum’ cultivation (shifting agriculture) system in north‐eastern India in litter bag experiments. The dynamics of decomposition varied between the crop residues and species studied. All the three studied types of residues of french bean and the leaves and roots of pea showed polynomial decomposition model with three distinct phases: an initial slow decomposition phase (1), followed by a faster decomposition rate (2) and again by a slow decomposition phase (3). However, the stems of pea plants showed an exponential increase in the decomposition rate during field incubation. Initial N, lignin, and lignin : N ratio were determined in crop residues. In general, roots decomposed slowly as compared to the leaves and stems due to greater lignin content. Soil microbial activity as determined by CO2 evolution was significantly correlated with the decomposition rates. Over all, the decay constants reveal that these fast decomposing leguminous crop residues can be properly managed for soil nutrient management in the low input shifting agricultural fields in the hills.

Kinetics and mechanism of the interaction of nitric oxide with pentacyanoferrate(II). Formation and dissociation of [Fe(CN)5NO]3 -.

The interaction of NO with [Fe(CN)(5)H(2)O](3)(-) (generated by aquation of the corresponding ammine complex) to produce [Fe(CN)(5)NO](3)(-) was studied by UV-vis spectrophotometry. The reaction product is the well characterized nitrosyl complex, described as a low-spin Fe(II) bound to the NO radical. The experiments were performed in the pH range 4-10, at different concentrations of NO, temperatures and pressures. The rate law was first-order in each of the reactants, with the specific complex-formation rate constant, k(f)( )()= 250 +/- 10 M(-)(1) s(-)(1) (25.4 degrees C, I = 0.1 M, pH 7.0), DeltaH(f)() = 70 +/- 1 kJ mol(-)(1), DeltaS(f)() = +34 +/- 4 J K(-)(1) mol(-)(1), and DeltaV(f)() = +17.4 +/- 0.3 cm(3) mol(-)(1). These values support a dissociative mechanism, with rate-controlling dissociation of coordinated water, and subsequent fast coordination of NO. The complex-formation process depends on pH, indicating that the initial product [Fe(CN)(5)NO](3)(-) is unstable, with a faster decomposition rate at lower pH. The decomposition process is associated with release of cyanide, further reaction of NO with [Fe(CN)(4)NO](2)(-), and formation of nitroprusside and other unknown products. The decomposition can be prevented by addition of free cyanide to the solutions, enabling a study of the dissociation process of NO from [Fe(CN)(5)NO](3)(-). Cyanide also acts as a scavenger for the [Fe(CN)(5)](3)(-) intermediate, giving [Fe(CN)(6)](4)(-) as a final product. From the first-order behavior, the dissociation rate constant was obtained as k(d) = (1.58 +/- 0.06) x 10(-)(5) s(-)(1) at 25.0 degrees C, I = 0.1 M, and pH 10.2. Activation parameters were found to be DeltaH(d)() = 106.4 +/- 0.8 kJ mol(-)(1), DeltaS(d)() = +20 +/- 2 J K(-)(1) mol(-)(1), and DeltaV(d)() = +7.1 +/- 0.2 cm(3) mol(-)(1), which are all in line with a dissociative mechanism. The low value of k(d) as compared to values for the release of other ligands L from [Fe(II)(CN)(5)L](n)()(-) suggests a moderate to strong sigma-pi interaction of NO with the iron(II) center. It is concluded that the release of NO from nitroprusside in biological media does not originate from [Fe(CN)(5)NO](3)(-) produced on reduction of nitroprusside but probably proceeds through the release of cyanide and further reactions of the [Fe(CN)(4)NO](2)(-) ion.

Changes in Chemical Components of Leaf Litter of Ginkgo Biloba during Mulching

The biological decomposition and chemical changes of leaf litter of Ginkgo biloba both at the surface and bottom layers were studied for 1 year. The changes in components such as the yields of 80% ethanol and water extractives, neutral sugars, uronic acids, Klason residues, acid-soluble phenolics, ash, nitrogen, and carbon were investigated. There were great drops of the yields of 80% ethanol extractives and water extractives in both surface and bottom mulch layers. Klason residues and sugars were the major components of the solid residues. The Klason residues lost 2.2% and 30.5% of their initial mass at the surface and bottom layers, respectively, during mulching. The total losses of the neutral sugars were 71.6% at the surface layer and 89.3% at the bottom layer. These results implied that the Klason residues were the most important inner component restraining the decomposition of the leaf litter of G. biloba and all analyzed cell wall components at the bottom layer had faster decomposition rates than those at the surface layer. Nitrogen content increased during one year of mulching, while changes in carbon contents were less than 1% throughout experiment.