ABSTRACT
With 15N isotope labeled maize straw in nylon net bags and buried in the wheat field at two N rates of 0 and 200 kg N·hm-2, the effects of nitrogen application on the decomposition of straw dry matter and the release dynamics of carbon, nitrogen, phosphorus and potassium (C, N, P and K) after maize straw retention were investigated in the winter wheat-summer maize rotation system in Guanzhong Plain, Shaanxi, China. Results showed that N application did not affect the decomposition of the returned straw C and dry matter, but promoted the release of P and inhibited the release of N and K from straw during sowing to wintering periods of winter wheat. From the grain filling to the harvest of winter wheat, the decomposition of the returned straw and the release of N, P and K were not affected, but the release of straw C was significantly enhanced by N application. The release dynamic of straw C was synchronized with the decomposition of the dry matter, and the C/N of straw declined gradually with the extension of wheat growing. Until the harvest of winter wheat, the accumulative decomposition rate of straw dry matter was less than 50%, and the total straw C release rate was around 47.9% to 51.1%. The C/N ratio of the returned straw was decreased from 32.2 to 20.2 and 17.9, respectively at N rates of 0 and 200 kg N·hm-2. From sowing to harvest of winter wheat, the net release of N, P and K from the straw was observed. The N release was 7.2-9.4 kg·hm-2 and 12.7%-16.6% of the total straw N, and the P release was 1.29-1.44 kg·hm-2 and 29.0%-32.4% of the total straw P, while a great deal of K was released quickly, with approximately 80% of the straw K released before wintering, 51.8-52.5 kg·hm-2 and 90.5%-91.7% of the total straw K released at wheat harvest. It was suggested that the K fertilizer application should be decreased for the winter wheat due to the great amount K release from the returned maize straw, and an extra amount of N and P fertilizer should be applied under the straw retention cropping system.
Subject(s)
Nitrogen , Zea mays , Agriculture , China , Fertilizers , Soil , TriticumABSTRACT
Porous anatase TiO2 spheres have been synthesized by a microwave-assisted hydrothermal reaction of spherical particle precursors followed by annealing in air. The synthesized TiO2 spheres are formed by interconnected nanocrystals with size of 8.7 nm in average and have grain diameters of 250-400 nm. After annealing at 500°C, the TiO2 samples maintain spherical shape and develop highly mesoporous characteristics with a specific surface area of 151 m(2) g(-1). The TiO2 samples annealed at 750°C consist of larger aggregated particles with diameters of 500-900 nm and still retain mesoporous anatase structure, but with a reduced specific surface area of 25.6 m(2) g(-1). Electrochemical studies reveal that the porous TiO2 spheres annealed at 500°C own very high and stable lithium ion (Li(+)) storage capacities of 207, 184, 166, and 119 mA h g(-1) at 0.5, 1, 2, and 5C (850 mA g(-1)) rates, respectively, owing to their highly porous nanostructures and fine spherical morphology. In contrast, the TiO2 spheres annealed at 700°C exhibit modest electrochemical performance due to their reduced pore structures and larger crystallite size. The prepared porous TiO2 spherical particles show great promise for use as high performance anode materials for lithium ion batteries (LIBs).
ABSTRACT
Hierarchical and porous V2O5 microspheres have been fabricated by a refluxing approach followed by annealing in air. The resulting porous V2O5 microspheres typically have diameters of 3-6 µm and are constructed of intertwined laminar nanocrystals or crosslinked nanobricks. It is found that the vanadyl glycolates rinsed with water have pronounced pore structures than that rinsed with ethanol alone. In addition, the configuration of the vanadyl glycolates microspheres can be tuned during the refluxing along with stirring. The possible formation processes of the vanadyl glycolates and V2O5 products have been discussed based on the experimental data. Electrochemical tests indicate that the hierarchical and porous V2O5 microspheres exhibit relatively high and stable Li(+) storage properties. The porous V2O5 microspheres assembled by intertwined nanoparticles maintain reversible Li(+) storage capacities of 102 and 80 mAh g(-1), respectively; whilst the porous V2O5 microspheres assembled by crosslinked nanobricks maintain reversible Li(+) storage capacities of 100 and 85 mAh g(-1) over 100 cycles at current rates of 0.5 and 1 C, respectively. The superior Li(+) storage performance of the hierarchical and porous V2O5 microspheres could mainly be ascribed to the improved electrode/electrolyte interface, reduced Li(+) diffusion paths, and relieved volume variation during lithiation and delithiation processes.
ABSTRACT
In this paper, soluble organic carbon (SOC) and nitrogen (SON) were extracted from manure, and their adsorption characteristics in Argosols and Anthrosols in Guanzhong region of Shaanxi Province were investigated. The results showed that the adsorption of SON and SOC in the two soils could be fitted by initial mass isotherm model, and the adsorbed amounts of SON and SOC had a significant linear relationship with the initial concentrations of SON and SOC added into soils. The partition coefficient, m of the initial mass isotherm model, indicated that Argosols had a higher adsorbility than Anthrosols. The average adsorption rates of SON and SOC in Anthrosols were 24.3% and 18.8%, and those in Argosols were 38.3% and 18.6%, respectively. The low adsorption rates of SON and SOC indicated their high mobility in the two soils, and more SON was adsorbed than SOC suggested the higher potential of SOC leaching from soil.
