Thermal,swelling and stability kinetics of chitosan based semi-interpenetrating network hydrogels

The present study is focused on studying the swelling kinetics, thermal and aqueous stabilities, and determination of various forms of water in the chitosan (CS) and polyacrylonitrile (PAN) blend and semi-interpenetrating polymer network (sIPN). CS/PAN blend hydrogel films were prepared by solution casting technique. The blend film with optimum swelling properties was selected for the synthesis of sIPN. CS in the blend was crosslinked with the vapors of Glutaraldehyde (GTA) to prepare sIPN. The fabricated CS/PAN blend and sIPN hydrogels films were characterized with Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA) and field emission scanning electron microscope (FESEM). The kinetics of swelling, bound and unbound waters and aqueous stability were determined experimentally. FESEM showed good miscibility between CS and PAN, FTIR showed no chemical interaction between CS and PAN; however, it did show a doublet for the sIPN, TGA showed improved thermal stability and swelling kinetic followed second order kinetics. The degree of swelling of the sIPN hydrogels samples at room temperature varied from ~2200 % (with a fair degree of stability (~30 %)) to ~1000 % (with high degree of aqueous stability (43 %)) with increase in the crosslinking time. The calculated unbound water (W_UB) max., for the blend was 52.3 % whereas for the bound (W_B) the max., was 41.9 %. However, for sIPN hydrogel films, the W_UB water decreased (max. 21.0 %) where as the W_B increased (max. 52.0 %). The decrease in W_UB and increase in the W_B is attributed to the formation of a compact structure and increase in the contact area between the water and polymers in sIPN hydrogels due to the induction of new water contacting point in these hydrogel films, respectively.     

Towards developing resistance to chickpea chlorotic dwarf virus through CRISPR/Cas9-mediated gene editing using multiplexed gRNAs

Journal of Plant Diseases and Protection - Mastreviruses are an emerging group of viruses transmitted by leafhoppers and infect both monocot and dicot plants. Chickpea chlorotic dwarf virus...     

Denitrification losses from an Inceptisol field treated with mineral fertilizer or sewage sludge

In order to evaluate the climatic and soil variables which control the denitrification processes in the field, measurements of N₂O-losses using the C₂H₂ inhibition technique were carried out in an Inceptisol cropped with spring wheat. The silty sand was amended with mineral fertilizer (120 kg N ha^?1) or additionally with sewage sludge (620 kg total N ha^?1). Soil temperature, moisture, nitrate and available carbon, the release of nitrous oxide (N₂O) from the soil surface as well as the N₂O concentrations along the soil profile were measured from March until November 1985 The N₂O surface fluxes from the inorganically fertilized field were well correlated with those from the sewage sludge amended plots (r = 0.76). Multivariate correlation analyses show that particularly soil moisture and nitrate content had a significant effect on the nitrate respiration. The correlation with the soil water content was more clearly expressed by the N₂O surface fluxes than by the N₂O concentrations of the soil air. The N₂O surface fluxes during 1985 totalled about 3 kg N ha^?1 in the minerally fertilized field. Sewage sludge amendments increased the N₂O evolution by 5 times. Spatial variability was high and the N₂O surface fluxes were not well correlated (r = 0.4) with the N₂O concentrations in the soil atmosphere. These experiments provide the background data for a denitrification model and better knowledge about the variables which have to be considered for its validation.     

Catechol and chlorocatechols in soil: Degradation and extractability

Catechol and chlorocatechols occur as intermediary metabolites during the degradation of naturally-occurring and synthetic aromatic compounds. Their degradation in soil was assessed under laboratory conditions using ¹⁴C-tracing techniques. Degradation of all compounds to CO₂ was rapid during the first 2 weeks (5–10% week^?1, but gradually decreased to below 1% week^?1 after 3 months. After 6 months. 44% of 4,5-dichlorocatechol, 38% of 4-chloro- and tetrachlorocatechols, and 30% of catechol were degraded to CO₂. In comparison, chlorophenols were degraded at similar rates, and chloroanilines were degraded more slowly. A mixed extradant of citric acid-ascorbic acid-acetone (1:1:2) was found to be most effective in extracting the catcchols from variously-treated soil samples. Recovery of added ¹⁴C from freshly fortified soils ranged from 74% for catechol to 98%, for tetrachlorocatechol. After equilibration of ¹⁴C-chemical with soil for 5–20 days, the extractability decreased to 38% for catechol, but remained over 86% for tetrachlorocatechol. Sterilization of soil before ¹⁴C addition had little effect on ¹⁴C extractability. After incubation of treated soil for 5 months, only 20–35% of residual ¹⁴C could be extracted. More than half of the nonextractable ¹⁴C-residues from incubated soil could be further removed by Na-pyrophosphate extraction.     

Decomposition of 14C-labelled melanoid fungal residues in a marginally sodic soil

Three melanoid fungi, namely Alternaria alternata, Curvularia lunata and Drechslera australiensis were grown on ¹⁴C-glucose and then fractionated into cell wall, cytoplasm and melanin. The decomposition of these fractions and their contribution to the stable organic matter fraction was studied in a marginally sodic soil. The rate of decomposition of fungal melanins was less than that of the cell wall or cytoplasm which had the highest rate of decomposition. However, the contribution of these fractions to the humic acid fraction was very low. Most of the ¹⁴C-activity was recovered in the humin fraction.     

Effect of montmorillonite and humate on growth and metabolic activity of some actinomycetes

In well-aerated culture solutions Ca-montmorillonite at 0.25% concentration markedly accelerated and increased growth, glucose consumption and CO₂ evolution by various Streptomyces, Micromonospora and Nocardia species. The montmorillonite was a little more active than Ca-humate and was usually still but somewhat less effective when confined to dialysis tubing. Ca-exchange resin, Na₂SiO₃ and finely powdered CaCO₃ exerted very little or no effect. In many cultures the relation of glucose consumption to biomass formation indicated a more efficient use of the glucose C for cell synthesis in the presence of clay. In other cultures the greater biomass formation was associated with a more rapid and complete utilization of the glucose present.     

Comparisons of soil organic matter and its fractions by pyrolysis mass-spectrometry

Pyrolysis mass-spectra from a sample of the A₁-horizon of a soil from southern Spain showed predominant peaks related to furan derivatives similar to those observed from complex polysaccharides in which not only hexoses but also pentoses and deoxyhexoses were constituent units. Smaller peaks, typical for protein materials and phenolic units, were also observed. On the other hand, typical peaks for the methoxyphenols of lignins were very small and indicated only limited amounts of undecomposed lignin residues in this soil sample. Peaks related to benzene or toluene were also very small.Humic acid samples from this soil showed much more prominent signals related to protein materials, benzene and phenolic derivatives and weaker polysaccharide-related signals than did the entire sample. Typical lignin related peaks were small or insignificant. Spectra from the grey or brown humidic acid fractions were much like those of the parent humic acid. Brown humic acid, however, showed stronger signals for nitrogen and sulphur compounds, indicating a higher content of protein-like materials in this fraction. Preparations of humic acid hydrolyzed by 6 N HCl showed in their pyrolysis products a marked increase in phenols and methoxyphenols.In its pyrogram, humin resembled humic acid, but signals for complex polysaccharides were more evident. Lignin-like materials seem not to be higher in this fraction. Hymatomelanic acid showed prominent signals related to polysaccharides and lignin. Pyrograms from the soil polysaccharides showed the characteristic pattern of a complex polysaccharide with the presence of fragments from polymers of amino acids or amino sugars. Fulvic acid spectra showed obvious dissimilarities to those from humic acid in that signals for protein, as well as those related to phenols, were low. Depending upon the isolation method, the fulvic acid preparations showed differing signals related to polysaccharide or phenolic materials.     

Dynamics of organic carbon and nitrogen in deep soil profile and crop yields under long-term fertilization in wheat-maize cropping system

Soil organic carbon (SOC) and nitrogen (N) are two of the most important indicators for agricultural productivity. The primary objective of this study was to investigate the changes in SOC and N in the deep soil profile (up to 100 cm) and their relationships with crop productivity under the influence of long-term (since 1990) fertilization in the wheat-maize cropping system. Treatments included CK (control), NP (inorganic N and phosphorus (P) fertilizers), NPK (inorganic N, P and potassium fertilizers), NPKM (NPK plus manure), and M (manure). Crop yield and the properties of topsoil were measured yearly from 2001 to 2009. C and N contents were measured at five different depths in 2001 and 2009. The results showed that wheat and maize yields decreased between 2001 and 2009 under the inorganic fertilizer (NP and NPK) treatments. The average yield between 2001 and 2009 under the NP, NPK, NPKM, and M treatments (compared with the CK treatment) increased by 38, 115, 383, and 381%, respectively, for wheat and 348, 891, 2 738, and 1 845%, respectively, for maize. Different long-term fertilization treatments significantly changed coarse free particulate (cfPOC), fine free particulate (ffPOC), intramicroaggregate particulate (iPOC), and mineral-associated (mSOC) organic carbon fractions. In the experimental years of 2001 and 2009, soil fractions occurred in the following order for all treatments: mSOC>cfPOC>iPOC>ffPOC. All fractions were higher under the manure application treatments than under the inorganic fertilization treatments. Compared to the inorganic fertilization treatments, manure input enhanced the stocks of SOC and total N in the surface layer (0–20 cm) but decreased SOC and N in the deep soil layer (80–100 cm). This reveals the efficiency of manure in increasing yield productivity and decreasing risk of vertical loss of nutrients, especially N, compared to inorganic fertilization treatments. The findings provide opportunities for understanding deep soil C and N dynamics, which could help mitigate climate change impact on agricultural production and maintain soil health.     

Impact of manure application on forms and quantities of phosphorus in a Chinese Cambisol under different land use

Purpose

It is critical to understand the effect of manure application on the availability of phosphorus (P) and the potential environmental contamination by runoff and leaching. However, previous studies generally focused on cultivated soil layer in single cropping systems. The aim of this study was to evaluate the effect of manure application on soil P forms and quantities to the 200 cm depth in a Chinese alkaline Cambisol in different cropping systems and the potential environmental implications.

Materials and methods

The sampling site, Shunyi District, is located in the peri-urban area of Beijing in the North China Plain, where large quantities of manure generated from intensive animal operations have been applied to agricultural fields. A field survey was carried out before sampling to identify soil sampling sites with long-term manure application and an adjacent area receiving no manure used for the same crop production. Soil samples from three cropping systems (vegetables, cereals, and trees) were vertically collected to a depth of 200 cm with the following depth increments: 0–20, 20–60, 60–90, 90–120, 120–160 and 160–200 cm. Soil samples were analyzed for plant-available P (Olsen P) and various P fractions by sequential P fractionation. Degree of P saturation (DPS) was also determined.

Results and discussion

Soil calcium bound P was the most abundant P fraction, followed by the residual P. Organic P only accounted for less than 5 % of total P in most of the soils. Manure application increased the levels of inorganic P (Pi), with higher proportions of Pi in labile forms than stable forms. After manure application for 8–15 year, available P (Olsen P) and DPS values of the 0–20 cm layer in all sites exceeded the threshold for Olsen P (60 mg?kg^?1) and DPS (30 %) and the risk of P loss by runoff is expected to significantly increase. The DPS values were generally lower than 30 % below 20 cm, indicating a minimal risk of P loss via leaching from deeper soil.

Conclusions

The results indicated that in typical peri-urban areas of the North China Plain, the on-going practice of manure application not only increased the size of each of the labile and non-labile P pools, but also caused a shift in the relative sizes of the different pools, regardless of the cropping systems. However, contrary to what was expected, soil P loss through surface runoff would be a greater concern than leaching following long-term manure amendment.     

Serological surveillance for Tahyna virus (California encephalitis orthobunyavirus,Peribunyaviridae) neutralizing antibodies in wild ungulates in Austria,Hungary and Romania

A serosurvey for Tahyna virus (TAHV), a mosquito‐borne California encephalitis orthobunyavirus (Peribunyaviridae) endemic to Europe, was performed to estimate the activity of TAHV on a broad geographic scale. Sera from wild boar (Sus scrofa), roe deer (Capreolus capreolus) and red deer (Cervus elaphus) were collected from Austria, Hungary and Romania. Samples were tested for neutralizing antibodies against TAHV using a virus microneutralization assay. The results demonstrate that TAHV transmission to mammals is widespread in Europe, particularly in the wild boar population where the mean rate of seroconversion is 15.2%.