Residues Decomposition in Crop Rotations under No-till System

Abstract The effectiveness soil cover in no-till is relating to quantity and quality of the phytomass produced by crops in rotation and, its persistence over the soil depends on residues decomposition. The objective of this study was to evaluate the phytomass production, decomposition rate and the half-life of crops in rotation at the Subtropical region, Brazil. The study was carried out at the Agronomic Institute of the Paraná (IAPAR), in Ponta Grossa, Parana State, Brazil. The experimental design was randomized blocks, with six treatments and four replicates. Winter cash crops and cover crops, single and in consortium, were evaluated in the year 2014 (wheat, black oats + hairy vetch + rye, black oats + ryegrass and black oats + blue lupine), in 2015 (canola, black oats, and black oats + hairy vetch + forage turnip) and in 2016 (barley, triticale, and triticale + black oats + rye). The phytomass was evaluating by collect three subsamples of 0.25 m2 per plot. For decomposition rate and the half-life of the crop residues, litter bags (LBs) methodology was used. A mathematical model (Q=Q0exp-kt) was used to represent the crop residues decomposition and the half-life of crop residues were obtained by the equation t1/2 = (ln2)/k. Poaceae consortia, single Poaceae and canola presented higher phytomass production when compared to Poaceae-Fabaceae consortia. The half-life for Poaceae-Fabaceae corsortia was shorter than single Poaceae.

Research Progress on the Determination of Electrical Conductivity in Forensic Science / 法医学杂志

Electrical conductivity （EC） is an important physical and chemical index in electrochemical analysis. In recent years, with the penetration and reference of transformation medicine and interdisciplinary theory and technology in the forensic field, new applications of EC in the field of forensic science have been developed. This paper reviews three aspects of the application of EC, the determination of biological tissue freshness, postmortem interval estimation and the application in forensic taphonomy, in order to provide reference for relevant scientific research and related practices.

La descomposición de la hojarasca como herramienta para evaluar la integridad funcional de ríos altoandinos del sur del Ecuador / Leaf-litter breakdown as a tool to assess the functional integrity of high Andean streams of Southern Ecuador

ResumenLas condiciones ecológicas de los ríos altoandinos tropicales estan amenazadas por numerosas actividades humanas que incluyen aquellas derivadas del cambio de la cobertura y uso del suelo de la cuenca. Para su evaluación se han propuesto protocolos que diagnostican el estado de la estructura pero no del funcionamiento de estos ecosistemas fluviales. En este trabajo se propone una herramienta de evaluación adaptada a las condiciones locales, incluyendo la metodología y los valores umbrales, utilizando el proceso de descomposición de la hojarasca como una medida del funcionamiento y salud de los ríos altoandinos del sur del Ecuador. Se seleccionaron 15 tributarios distribuidos en tres microcuencas (Mazán, Llaviuco y Matadero) dentro o en las adyacencias del Parque Nacional Cajas. En cada tributario se incubaron bolsas de descomposición elaboradas con dos tipos de malla (gruesa y fina) para separar la contribución de macroinvertebrados y microorganismos en el proceso. Como substrato vegetal se emplearon hojas de Alnus acuminata y Miconia bracteolata. Las bolsas fueron colocadas en los ríos y mantenidas durante 15, 28 y 64 días. Las tasas de descomposición (-K) fueron obtenidas a partir del período de tiempo en el cual se produjo la pérdida de aproximadamente el 50 % de la masa seca libre de ceniza. En cada período de recolección se determinaron parámetros físicos y químicos. Adicionalmente, se aplicaron los índices de calidad de ribera (QBR-And) y de habitat fluvial (IHF). Para la elaboración de los umbrales de condición funcional se utilizaron las métricas Ktotal y el cociente entre la tasa de descomposición en malla gruesa y malla fina (Kg/Kf). Para probar la sensibilidad de las métricas se emplearon métodos gráficos, Anova de una vía y se calculó la eficiencia discriminativa (ED) de las mismas. Los resultados del análisis de usos y coberturas del suelo revelaron un gradiente de intervención Matadero ≥ Llaviuco > Mazán. La composición de las variables ambientales de las corrientes de la microcuenca Mazán resultaron diferentes con respecto a las de Llaviuco y Matadero, cuyos valores parecen ser más semejantes entre sí. La evaluación de la calidad de ribera mediante el índice QBR-And muestra un gradiente importante desde valores muy bajos en las corrientes de Matadero (27.5), valores medios a altos en Llaviuco (66.5) y valores más altos en los tributarios de Mazán (87). Las tasas de descomposición de la hojarasca de los tributarios de la microcuenca del Río Mazán resultaron significativamente más rápidas que en los tributarios de los Ríos Matadero y Llaviuco para las hojas de A. acuminata pero no para las hojas de Miconia. La métrica Kg/Kf se consideró sensible y suficiente para discriminar los impactos en las áreas estudiadas. Los valores del cociente Kg/Kf resultaron significativamente mayores en Mazán en comparación a Llaviuco y Matadero, que no resultaron diferentes entre sí. Nuestros resultados apoyan la utilización del proceso de descomposición de la hojarasca como una herramienta adecuada para evaluar la condición ecológica funcional, complementando las evaluaciones estructurales, de los ríos altoandinos.

Abstract:The ecological condition of tropical Andean rivers are threatened by many human activities including changes in land use and cover in watersheds. Current protocols diagnose the structural condition of streams but not their function. In this study we proposed an assessment tool using the leaf-litter breakdown as a measure of the functional condition and health of high Andean streams in Southern Ecuador, including methodology and threshold values adapted to local conditions. We selected 15 streams in three micro-basins (Mazán, Llaviuco and Matadero) within or in the vicinity of Cajas National Park where we deployed litterbags for 15, 28 and 64 days. We used two types of mesh (coarse and fine) for the litterbags in order to separate the contribution of macro-invertebrates and microorganisms in the decomposition process and also tested two different leaf substrates: Alder (Alnus acuminata) and Miconia (Miconia bracteolata). In each collection period we determined physical and chemical parameters, applied the riparian quality index (QBR-And) and river habitat index (IHF). Decomposition rates (-k) were determined from the time period at which approximately 50 % ash-free mass would have been lost. We used Ktotal and the ratio of the rate of decomposition between coarse and fine mesh (Kg/Kf) to define the functional condition thresholds. To test the metrics sensitivity we used graphical methods, one-way ANOVA and discriminative efficiency (ED). The analysis of watershed land-use and cover showed a gradient of intervention: Matadero ≥ Llaviuco > Mazán. The composition of the environmental variables of Mazán streams were different with respect to Llaviuco and Matadero, whose values were similar to each other. The QBR-And index showed a significant gradient from very low levels in Matadero (27.5), moderately high values in Llaviuco (66.5) to high values in Mazán (87). Alder leaf-litter breakdown rates were significantly faster in Mazán than in Matadero and Llaviuco streams, while breakdown rates of Miconia were not significantly different among watersheds. The Kg/Kf ratio was significantly higher in Mazán compared to Llaviuco and Matadero, which did not differ. We consider the Kg/Kf metric sensitive enough to discriminate impacts in the studied areas. Our results support the use of the leaf-litter breakdown as an appropriate tool to assess functional ecological condition, complementing the structural assessments of these Andean rivers. Rev. Biol. Trop. 65 (1): 321-334. Epub 2017 March 01.

Relationship between Electrical Conductivity and Decomposition Rate of Rat Postmortem Skeletal Muscle / 法医学杂志

OBJECTIVES@#To analyze the relationship among electrical conductivity （EC）, total volatile basic nitrogen （TVB-N）, which is an index of decomposition rate for meat production, and postmortem interval （PMI）. To explore the feasibility of EC as an index of cadaveric skeletal muscle decomposition rate and lay the foundation for PMI estimation.@*METHODS@#Healthy Sprague-Dawley rats were sacrificed by cervical vertebrae dislocation and kept at 28 ℃. Muscle of rear limbs was removed at different PMI, homogenized in deionized water and then skeletal extraction liquid of mass concentration 0.1 g/mL was prepared. EC and TVB-N of extraction liquid were separately determined. The correlation between EC (x₁) and TVB-N (x₂) was analyzed, and their regression function was established. The relationship between PMI (y) and these two parameters were studied, and their regression functions were separately established.@*RESULTS@#The change trends of EC and TVB-N of skeletal extraction liquid at different PMI were almost the same, and there was a linear positive correlation between them. The regression equation was x₂=0.14x₁-164.91(R²=0.982). EC and TVB-N of skeletal muscle changed significantly with PMI, and the regression functions were y=19.38x₁³-370.68x₁²+2 526.03 x₁-717.06(R²=0.994), and y=2.56x₂³-48.39x₂²+330.60x₂-255.04(R²=0.997), respectively.@*CONCLUSIONS@#EC and TVB-N of rat postmortem skeletal muscle show similar change trends, which can be used as an index for decomposition rate of cadaveric skeletal muscle and provide a method for further study of late PMI estimation.

Eichhornia azurea decomposition and the bacterial dynamic: an experimental research

Abstract Organic decomposition is a complex interaction between chemical, physical and biological processes, where the variety of aquatic vascular plants is essential for the trophic dynamics of freshwater ecosystems. The goal of this study was to determine the aquatic macrophyte Eichhornia azurea (Sw.) Kunth decomposition rate, the time relation with the limnological parameters, and whether this relationship is a result of decomposition processes. To that end, we collected water and leaves of E. azurea in Surf Leopoldo, PR. The experiment consisted of two treatments: 25 containers with 450 mL of water and 0.8 g of biomass dry weight were used with or without the addition of macrophytes. Samples were collected in triplicate at times 0, 3 h, 6 h, 12 h, 24 h, 72 h, 120 h, 168 h and 240 h. When the container was removed, the plant material was dried in an oven. After 48 h, the material was measured to obtain the final dry weight. Analyses of pH, conductivity, dissolved oxygen, total phosphorus N-ammonia (NH4), soluble reactive phosphorus (PO4) and dissolved organic carbon were performed, and the decomposition rate was calculated. The results showed significant temporal variation of limnological parameters in the study. Additionally, dissolved oxygen, conductivity, dissolved organic carbon and total phosphorus were correlated with the dry weight of the biomass, suggesting that E. azurea decomposition significantly interferes with the dynamics of these variables.

Assessment of litter degradation in medicinal plants subjected to ultraviolet-B radiation.

Litter decomposition is an important component of global carbon budget. Elevated influx of ultraviolet-B radiation (UV-B) as a consequence of depletion of stratospheric ozone (O3) layer may affect litter decomposition directly or/ modifying the plant tissue quality. Chemical composition of plant can affect litter decomposition. In the present study, three important medicinal plant species i.e. Acorus calamus, Ocimum sanctum and Cymbopogon citratus were exposed to two levels of supplemental UV-B (sUV1 and sUV2) during the growth period and examined the changes in leaf quality and degradation of leaf litters. The sUV2 treatment (+3.6 kJ m-2 d-1) increased the rate of decomposition by 45% and 31% respectively; in leaf litters from O. sanctum and C. citratus, while no significant effect was noticed in A. calamus leaf litter. Higher accumulation of sclerenchymatous tissue around vascular bundles and increased concentrations of total phenols by 39 mg g-1 probably lowered the decomposition rate; finding k value: 0.0049 g g-1 d-1 in leaf litters of A. calamus. The C/ N ratio was increased by 14% at sUV2 in C. citratus, whereas in O. sanctum it decreased by 13.6% after treatment. Results of the present experiment illustrates that firstly UV-B can modify the decomposition rate of leaf litter of test plant species, secondly it can alter the tissue chemistry particularly leaf phenolics, N and P concentrations strongly and thus affecting the decay rate and thirdly UV-B effects on decay rate and leaf chemistry is species specific.

Persistência e liberação de macronutrientes e silício da fitomassa de crotalária em função da fragmentação / Persistence and release of macronutrients and silicon of sunnhemp phytomass as affected by fragmentation

A persistência da palhada, bem como, a dinâmica de liberação de nutrientes, são importantes aspectos a se considerar na escolha de plantas para composição das rotações de culturas em sistema plantio direto. Assim, objetivou-se com esse trabalho avaliar a taxa de decomposição e a velocidade de liberação de macronutrientes e silício (Si), da fitomassa de crotalária (Crotalaria juncea L.), em função do manejo, sem e com fragmentação. O delineamento experimental foi de blocos casualizados, com quatro repetições, em esquema fatorial 2x6, constituído por dois manejos da fitomassa da parte aérea aos 75 dias após emergência (sem e com fragmentação mecânica) e seis épocas de coleta (0, 18, 32, 46, 74 e 91 dias após manejo (DAM)), onde foram avaliadas a taxa de decomposição e a liberação de nutrientes da fitomassa da crotalária. A fragmentação mecânica da palhada da crotalária não alterou a decomposição e a liberação de macronutrientes. As máximas taxas de liberação diária ocorreram de 0 a 18 DAM. O K é o nutriente mais rapidamente disponibilizado, enquanto que o Si é o elemento liberado mais lentamente ao solo. Com o passar do tempo ocorreu aumento do teor de Si na palhada.p

The persistence of straw, as well as the dynamics of nutrients release of it, are important aspects to consider in the choice of plants for composition of crop rotations in a no tillage system. Thus, the objective of this work was to evaluate the decomposition rate and macronutrients and silicon (Si) release from sunn hemp (Crotalaria juncea L.) phytomass, as a function of management, with and without fragmentation. A randomized blocks design, with four replications, in a factorial 2x6, constituted by two aboveground phytomass management after 75 days after emergence (with and without mechanical fragmentation) and six sampling times (0, 18, 32, 46, 74 and 91 days after management (DAM)), were evaluated the decomposition rate and nutrient release from sunn hemp biomass. The mechanical fragmentation of sunn hemp straw did not change the decomposition and macronutrients release. The maximum release rates occurred 0-18 DAM. Potassium is the most rapidly available nutrient, while the silicon is more slowly released to the ground. Over time there has been increasing Si content in the straw.