Controlled-release urea (CRU) has better characteristics than conventional urea for synchronizing nitrogen (N) release with plant uptake.  Understanding the effects of CRU on crop yield and N use efficiency (NUE) has long been the key to evaluate the performance of CRU.  A long-term experiment over five consecutive years was conducted in Changsha, Hunan Province, China, to investigate the effects of polyethylene-coated urea with a 90-d release period on the yield and NUE of double rice (early and late crops are grown in the same year), the amount of residual soil mineral N and the soil–plant N balance, as well as on the economic benefits.  Four N fertilizer treatments including CK (no N fertilizer), U (conventional urea), CRU1 (polyethylene-coated urea with equal N application rate to U) and CRU2 (20% reduction in N application rate of CRU1) were established.  The results indicated that CRU1 application increased the yield and NUE of double rice by 11.0 and 13.5%, respectively, compared with U.  Higher yield and NUE of late rice were found than in early rice in CRU treatments.  Compared with conventional U, the yield and NUE of early rice in the CRU1 treatment were increased by 6.0 and 10.2%, respectively, and those of late rice were increased by 15.4 and 13.8%, respectively.  There was no significant difference between CRU1 and CRU2 in double rice yield.  Furthermore, CRU treatments (including CRU1 and CRU2) had higher apparent residual N_min rate (ARNR) and apparent N recovery rate (ANRR), but lower apparent N loss (N_S) than the conventional U treatment.  Concentrations of NH₄⁺-N and NO₃^–-N were greater in the surface soil (0–20 cm) and lower in the deeper soil layer (40–60 cm) with CRU treatments than in the U treatment after harvest.  Moreover, CRU application produced a greater economic benefit than conventional U application.  In general, CRU outperformed U fertilizer in terms of rice yield, NUE, soil–plant N balance, economic benefit, and CRU2 provided greater comprehensive benefits than CRU1.  It is suggested that CRU application is beneficial for solving N management challenges in the production of rice.

Polyimide (PI) is a type of important membrane material. A soluble polymer was synthesized from 4,4´-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and 2,2-bis[4-(4-aminophenoxy) phenyl] hexafluoropropane (BDAF) by the two-step polymerization method. The polymer was proved to be polyimide 6FDA-BDAF by the Fourier transform infrared (FT-IR), the 1H-NMR and 19F-NMR spectra. An asymmetric membrane was prepared with the synthesized polyimide 6FDA-BDAF, it was porous in the 50 μm height bulk and dense in a 3–5 μm height surface. The membrane was used to separate n-heptane/ thiophene mixtures by pervaporation with sulfur (S) contents from 50 to 900 μg g–1. The total flux was enlarged from 7.96 to 37.61 kg m–2 h–1 with temperature increasing from 50 to 90°C. The membrane’s enrichments factor for thiophene were about 3.13 and dependent on the experimental conditions. The experimental results demonstrated that polyimide 6FDA-BDAF would be a potential membrane material for desulfurization and controlled release of the S-containing fertilizer.

Exploration of soil environmental characteristics governing soil microbial community structure and activity may improve our understanding of biogeochemical processes and soil quality. The impact of soil environmental characteristics especially organic carbon availability after 15-yr different organic and inorganic fertilizer inputs on soil bacterial community structure and functional metabolic diversity of soil microbial communities were evaluated in a 15-yr fertilizer experiment in Changping County, Beijing, China. The experiment was a wheat-maize rotation system which was established in 1991 including four different fertilizer treatments. These treatments included: a non-amended control (CK), a commonly used application rate of inorganic fertilizer treatment (NPK); a commonly used application rate of inorganic fertilizer with swine manure incorporated treatment (NPKM), and a commonly used application rate of inorganic fertilizer with maize straw incorporated treatment (NPKS). Denaturing gradient gel electrophoresis (DGGE) of the 16S rRNA gene was used to determine the bacterial community structure and single carbon source utilization profiles were determined to characterize the microbial community functional metabolic diversity of different fertilizer treatments using Biolog Eco plates. The results indicated that long-term fertilized treatments significantly increased soil bacterial community structure compared to CK. The use of inorganic fertilizer with organic amendments incorporated for long term (NPKM, NPKS) significantly promoted soil bacterial structure than the application of inorganic fertilizer only (NPK), and NPKM treatment was the most important driver for increases in the soil microbial community richness (S) and structural diversity (H). Overall utilization of carbon sources by soil microbial communities (average well color development, AWCD) and microbial substrate utilization diversity and evenness indices (H’ and E) indicated that long-term inorganic fertilizer with organic amendments incorporated (NPKM, NPKS) could significantly stimulate soil microbial metabolic activity and functional diversity relative to CK, while no differences of them were found between NPKS and NPK treatments. Principal component analysis (PCA) based on carbon source utilization profiles also showed significant separation of soil microbial community under long-term fertilization regimes and NPKM treatment was significantly separated from the other three treatments primarily according to the higher microbial utilization of carbohydrates, carboxylic acids, polymers, phenolic compounds, and amino acid, while higher utilization of amines/amides differed soil microbial community in NPKS treatment from those in the other three treatments. Redundancy analysis (RDA) indicated that soil organic carbon (SOC) availability, especially soil microbial biomass carbon (Cmic) and Cmic/SOC ratio are the key factors of soil environmental characteristics contributing to the increase of both soil microbial community structure and functional metabolic diversity in the long-term fertilization trial. Our results showed that long-term inorganic fertilizer and swine manure application could significantly improve soil bacterial community structure and soil microbial metabolic activity through the increases in SOC availability, which could provide insights into the sustainable management of China’s soil resource.