Efficacy, uptake and distribution of different herbicides in the water hyacinth

Experiment conducted in the glasshouse with water hyacinth plants in pots revealed that 3h.after spraying parquet or 2.4-D at recommendeb herbicida rates, 43 to 53, of the herbicide is found in the plants and the rest is present in the water culture Out of the total [¹⁴Clparaquat applied,38,9,8·8. 32 and 0.9% was found in the leaf blads. petioles, underwater foliage and roots respectively. The corresponding values for [¹⁴C]2, 4-D were 320. 94. 13 and 0.2% As the time interval after spraying increased, a greater accumulation of herbicide in the under-water parts was evident A net loss of 14 and 60%. of the applied 2,4-D was recorded 1 and 2 weeks after spraying respectively the rate of paraquat loss from the plant water system was similar to 2,4-D. Absorption of [¹⁴C]2,4-D from the culture solution by the roots and the floats of the water hyacinth was. evident Translocation of root-absorbed 2, 4-D into the meristematic folrar parts was dernonstrated If the substrates was treated with 2,4-D.a minimal concentration of 1 p. p. m. was required for water hyacinth death In another experiment glyphosite at 2 to 6 kg a 1 ha and 2.4-D.amine at 0–75 2.25 kg a ha gave complete control of water hyacinth Asulam was found to be unsatis factory even at 6 kg a.1 ha the highest rate tried.     

Elemental Sulfur Oxidation by Thiobacillus spp. and Aerobic Heterotrophic Sulfur-Oxidizing Bacteria

The prediction of the oxidation rate of elemental sulfur (S 0 ) is a critical step in sulfur (S) fertilizer strategy to supply plant-available sulfur. An incubation experiment was conducted to determine the rate and amount of S 0 oxidation in relation to the contribution of Thiobacillus spp. and aerobic heterotrophic S-oxidizing bacteria. After 84 days, 16.3% and 22.4% of the total S 0 applied to the soil were oxidized at 20 and 30-C, respectively. The oxidation of S 0 proved to be a two-step process with a rapid oxidation during the first 28 days and a slow oxidation from then on. The highest oxidation rate of 12.8 μg S cm-2 d-1 was measured during the first two weeks at 30-C. At 20-C the highest oxidation rate of 10.2 μg S cm-2 d-1 was obtained from two to four weeks after start of the experiment. On an average the soil pH declined by 3.6 and 4.0 units after two weeks of experiment. At the same time the electric conductivity increased nine times. With the oxidation of S 0 the population of Thiobacillus spp. and aerobic heterotrophic S-oxidizing bacteria increased. The corresponding values for Thiobacillus spp. and aerobic heterotrophic S-oxidizing bacteria increased from 2.9 × 10 5 and 1.4 × 10 5 g-1 soil at the start of the experiment to 4 × 10 8 and 5.6 × 10 8 g-1 soil 14 days after S 0 application, respectively. No Thiobacillus spp. was present eight weeks after S 0 application. The results suggested that oxidation of residual S 0 completely relied on aerobic heterotrophic S-oxidizing bacteria.     

应用反射光谱法估测矿区附近农田土壤As, Cu污染

Concentrations of Iron (Fe), As, and Cu in soil samples from the fields near the Baoshan Mine in Hunan Province, China, were analyzed and soil spectral reflectance was measured with an ASD FieldSpec FR spectroradiometer (Analytical Spectral Devices, Inc., USA) under laboratory condition. Partial least square regression (PLSR) models were constructed for predicting soil metal concentrations. The data pre-processing methods, first and second derivatives (FD and SD), baseline correction (BC), standard normal variate (SNV), multiplicative scatter correction (MSC), and continuum removal (CR), were used for the spectral reflectance data pretreatments. Then, the prediction results were evaluated by relative root mean square error (RRMSE) and coefficients of determination (R²). According to the criteria of minimal RRMSE and maximal R², the PLSR models with the FD pretreatment (RRMSE = 0.24, R² = 0.61), SNV pretreatment (RRMSE = 0.08, R² = 0.78), and BC-pretreatment (RRMSE = 0.20, R² = 0.41) were considered as the final models for predicting As, Fe, and Cu, respectively. Wavebands at around 460, 1 400, 1 900, and 2 200 nm were selected as important spectral variables to construct final models. In conclusion, concentrations of heavy metals in contaminated soils could be indirectly assessed by soil spectra according to the correlation between the spectrally featureless components and Fe; therefore, spectral reflectance would be an alternative tool for monitoring soil heavy metals contamination.     

Effects of tillage on microbial populations associated to soil aggregation in dryland spring wheat system

Tillage may influence the microbial populations involved in soil aggregation. We evaluated the effects of no till (NT) and conventional tillage (CT, tillage depth about 7 cm) continuous spring wheat system on culturable heterotrophic bacterial communities predominant in microaggregates (0.25–0.05 mm) and on soil-aggregating basidiomycete fungi in aggregate-size classes (4.75–2.00, 2.00–0.25, and 0.25–0.05 mm) at 0–20 cm depth of a Williams loam (fine-loamy, mixed, Typic Argiustolls) in dryland Montana, USA. Enzyme-linked immunosorbent assay used to quantify antigenic response to basidiomycete cell walls, was higher in NT than in CT in 4.75–2.00 mm size class in 2007 and higher in all classes and years at 0–5 cm depth, but was not different between tillage, years, and classes at 5–20 cm. The culturable bacteria from microaggregates were subjected to a soil sedimentation assay to determine their soil binding capability. The proportion of isolates which can function as soil aggregators was higher in NT than in CT at 0–5 cm but was not different at 5–20 cm. Our results provide a first insight into the beneficial effects of dryland NT compared to CT in reducing soil disturbance and residue incorporation and enriching the proportion of microorganisms responsible for aggregation, especially at the soil surface.     

ADSORPTION, DESORPTION AND SOLUBILITY RELATIONSHIPS OF LEAD AND CADMIUM IN SOME ALKALINE SOILS

In some alkaline soils of Punjab (India) the adsorption, desorption and solubility relationships of lead and cadmium were investigated and the results analysed by the Langmuir equation. Both the metals are retained in soils by adsorption on mineral interfaces and interaction with organic matter and calcium carbonate. At high concentrations, these probably precipitate as hydroxides. Sequential desorption of Pb and Cd with 1 MKCI and 0.05 MCu(CH₃COO)₂ provided a measure of their exchangeable and chelated form.     

A model for predicting the fate of nitrogen fertilizer in lowland ricefields

Equations are developed for the simultaneous movement and reaction in flooded soils of urea, ammoniacal species, carbonate species, and acids and bases, the simultaneous uptake of N by a developing rice root system, and losses of NH₃ and CO₂ by volatilization from the floodwater. The equations allow for the initial distribution of urea and other reactants in the soil and floodwater, for movement both by diffusion and convection, and for the rates of urea hydrolysis, floodwater algal activity, organic-C and -N mineralization, and H+ release from roots to balance excess uptake of cations over anions. The equations are combined in a computer model which can predict the fate of N fertilizer in lowland ricefields for any combination of crop and environmental conditions.     

Microplastics in soil: Impacts and microbial diversity and degradation

Microplastics(MPs) are plastic particles less than 5 mm in size that have become a major environmental pollutant due to their ubiquitous and persistent nature. Microplastic contamination of the aquatic environment has received the most attention so far, whereas the current understanding of MP prevalence and its impacts in the terrestrial environment is largely limited. The MP contamination of soil can cause bioaccumulation and toxicity in terrestrial animals and plants, which can consequently affect human health. This review is aimed towards combining the available information on the occurrence, sources, and effects of MPs on the different aspects of the terrestrial environment and to highlight the limitations in our knowledge regarding the nature and impacts of MPs in soil. The review also highlights microbial degradation of MPs as an advancing research area, with numerous microorganisms being identified as capable of efficiently degrading this persistent contaminant.     

CONTRAST MEDIA ENHANCEMENT OF INTRACRANIAL LESIONS IN MAGNETIC RESONANCE IMAGING DOES NOT REFLECT HISTOPATHOLOGIC FINDINGS CONSISTENTLY

Certain magnetic resonance (MR) enhancement patterns are often considered to be associated with a specific diagnosis but experience shows that this association is not always consistent. Therefore, it is not clear how reliably contrast enhancement patterns correlate with specific tissue changes. We investigated the detailed histomorphologic findings of intracranial lesions in relation to Gadodiamide contrast enhancement in 55 lesions from 55 patients, nine cats, and 46 dogs. Lesions were divided into areas according to their contrast enhancement; therefore 81 areas resulted from the 55 lesions which were directly compared with histopathology. In 40 of 55 lesions (73%), the histomorphologic features explained the contrast enhancement pattern. In particular, vascular proliferation and dilated vessels occurred significantly more often in areas with enhancement than in areas without enhancement (P=0.044). In 15 lesions, there was no association between MR images and histologic findings. In particular, contrast enhancement was found within necrotic areas (10 areas) and ring enhancement was seen in lesions without central necrosis (five lesions). These findings imply that necrosis cannot be differentiated reliably from viable tissue based on postcontrast images. Diffusion of contrast medium within lesions and time delays after contrast medium administration probably play important roles in the presence and patterns of contrast enhancement. Thus, histologic features of lesions cannot be predicted solely by contrast enhancement patterns.     

Changes in particulate and mineral-associated organic carbon with land use in contrasting soils

Soil organic carbon(SOC) is the largest terrestrial carbon(C) stock, and the capacity of soils to preserve organic C(OC) varies with many factors,including land use, soil type, and soil depth. We investigated the effect of land use change on soil particulate organic matter(POM) and mineral-associated organic matter(MOM). Surface(0–10 cm) and subsurface(60–70 cm) samples were collected from paired sites(native and cropped) of four contrasting soils.Bulk soils were separated into POM and MOM fract...