Field experiments were conducted to study the effects of nitrogen application rates and straw returning on grain yield, nutrient accumulation, nutrient release from straw and nutrient balance in late sowing wheat. The results showed that straw returning together with appropriate application of nitrogen fertilizer improved the grain yield. Dry matter, nitrogen, phosphorus and potassium accumulation increased significantly as the nitrogen application rate increased.
View Article and Find Full Text PDFField experiments were conducted to study the effects of varying rates of nitrogen application on soil mineral nitrogen content, amount of nitrogen released from the straw, and grain yield of late sowing wheat with straw returning. The result showed that a high nitrogen fertilizer application rate enhanced the mineral nitrogen content in the soil layer of 0 to 50 cm, and also in the lower soil layers when using N at 270 and 360 kg · hm(-2) with the advance of growth stages. The amount of nitrogen released form the straw increased as the nitrogen application rate increased; the lowest appeared from overwintering to jointing, and the highest from jointing to maturity.
View Article and Find Full Text PDFA two-year (2009-2011) field experiment was conducted to study the effects of different tillage modes, straw-returning, and their interactions on the soil total organic carbon (TOC) and labile organic carbon (LOC) components (easily oxidizable organic carbon (EOC), water-soluble organic carbon (WSOC), and microbial biomass carbon (MBC)) at the soil depths of 0-7, 7-14, and 14-21 cm in a farmland with rice-wheat double cropping. In all treatments of straw-returning, the TOC and LOC contents in each soil layer were significantly higher than those without straw-returning. Under plowing tillage, the MBC content in 0-7 cm soil layer was significantly higher than that under rotary tillage, but the EOC content was in adverse.
View Article and Find Full Text PDFComposite nanoparticles with magnetic core and fluorescent shell were facilely prepared by the layer-by-layer deposition of conjugated polyelectrolytes over the negatively charged nanoparticles (NPs) of superparamagnetic iron oxide. The alternate assembly of cationic and anionic fluorescent polyelectrolytes leads to reversal in the sign of zeta-potentials. The even numbers of adsorption layer corresponding to the anionic polyelectrolyte (PFS) have negative values (-13 to -24 mV), whereas odd numbers of coating relative to the cationic polyelectrolyte (PFN) have positive values (26 to 28 mV).
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