Reduction of nitrous oxide emission by using stearic acid combined zinc coated urea in silty clay and sandy loam soils under bare and planted conditions.

Overuse of chemical fertilizers in agroecosystems leads to the increased economic burden, low crop production in terms of input and environmental pollution. Due to its improved nutrient management and degrading properties, synthetic slow release fertilizers have become a significant advancement in the fertilizer sector. In this study we evaluated the effect of slow release urea on nitrous oxide (N2O) emission, crop growth and crop nutrient contents. Measurements were carried out in two different texture soils (sandy loam and silty clay) under two different conditions (bare soil and planted). The N2O emission was measured for 15 days from bare soils and 48 days from planted soil. Plant fresh weight, dry weight, chlorophyll contents, N and Zn were measured in the end of the experiment. The results showed that N2O emission was reduced 33-39 % from coated urea as compared to conventional urea in bare soil. In planted soil, the coated urea reduced the N2O emission 29-33 %. The deep placement of urea in silty clay soil reduced the N2O emission up to 22.8 % as compared to surface placement. Plant fresh matter, dry matter, N and Zn contents were significantly (p ≤ 0.05) higher with coated urea as compared to conventional urea. It is concluded that the coating of urea with hydrophobic materials like stearic acid, along with Zn sources i.e. Zn fortified nano-bentonite or the ZnO nanoparticles (NPs) presents opportunities to overcome the environmental pollution and increasing the crop production and quality.

Two potential equilibrium states in long-term soil respiration activity of dry grasslands are maintained by local topographic features.

Soil respiration of grasslands is spatio-temporally variable reflecting the changing biological activities of the soil. In our study we analysed how the long-term soil respiration activities of dry grasslands would perform in terms of resistance and resilience. We also investigated how terrain features are responsible for response stability. We conducted a 7-year-long spatial study in a Hungarian dry grassland, measuring soil respiration (Rs), soil temperature (Ts) and soil water content (SWC) along 15 measuring campaigns in 80 × 60 m grids and soil organic carbon content in 6 of the occasions. Two proxy variables were introduced to grasp the overall Rs activity, as well as its temporal stability: average rankRs, the temporal average Rs rank of a measuring position from the campaigns revealed the persistent spatial pattern of Rs, while rangeRs, the range of ranks of the positions from the campaigns described the amplitude of the Rs response in time, referring to the response stability in terms of resistance or resilience. We formulated a hypothetic concept of a two-state equilibrium to describe the performance of the long-term Rs activity: Rs activity with smaller rangeRs, that is both the lower elevation positions with larger rankRs ("state I") and the higher elevation positions with smaller rankRs ("state II") correspond to an equilibrium state with several terrain attributes being responsible for the equilibrium responses. Majority of the measuring positions was belonging to none of these equilibrium states. These positions showed higher rangeRs for medium rankRs, suggesting resilience (not resistance) as a major strategy for this ecosystem.

Separating the effects of temperature and carbon allocation on the diel pattern of soil respiration in the different phenological stages in dry grasslands.

Diel variability of soil respiration is influenced by several factors including temperature and carbon allocation as the most significant ones, co-varying on multiple time scales. In an attempt to disentangle their effects we analyzed the dynamics of soil respiration components using data from a three-year soil respiration study. We measured CO2 efflux in intact, root-excluded and root- and mycorrhizal fungi excluded plots and analyzed the diel variability in different phenological stages. We used sine wave models to describe the diel pattern of soil respiration and to disentangle the effects of temperature from belowground carbon allocation based on the differences between component dynamics inferred from the fitted models. Rhizospheric respiration peaked 8-12 hours after GPP peak, while mycorrhizal fungi respiration had a longer time lag of 13-20 hours. Results of δ13CO2 isotopic signals from the respiration components showed similar patterns. It was found that drought affected the component respiration rates differently. Also, the speed and the amount of carbon allocation to the roots as well as to the mycorrhizal fungi was reduced under drought. We conclude that the diel variability of soil respiration is the result of the integrated patterns of temperature- and carbon allocation-driven components in dry grasslands and their share depends on their phenological stages and stress state.

Phase-Separable Polyisobutylene Palladium-PEPPSI Precatalysts: Synthesis and Application in Buchwald-Hartwig Amination.

This paper reports the efficient synthesis of the first class of polyisobutylene(PIB)-supported palladium-PEPPSI precatalyst (PEPPSI = pyridine-enhanced precatalyst preparation, stabilization, and initiation). The new complexes are employed in Buchwald-Hartwig amination of aryl chlorides and are found to be reasonably active in the titled cross-coupling reaction. The supported catalysts are tested in polar (1,4-dioxane and 1,2-dimethoxyethane) as well as in aliphatic reaction media (toluene and n-heptane) and display superior activity in the highly lipophilic solvent (n-heptane). The catalytic efficacy of PIB-Pd-PEPPSI precatalyst is measured to be comparable to its nonsupported analog. Pd-leaching is determined by inductively coupled plasma mass spectrometry (ICP-MS) after a simple liquid/liquid extraction and is found to be 2 ppb in the product phase, translating into a recovery of ≈99.8% of the palladium.

Convenient protocols for Mizoroki-Heck reactions of aromatic bromides and polybromides with fluorous alkenes of the formula H2C[double bond, length as m-dash]CH(CF2)n-1CF3 (n = 8, 10).

The fluorous alkenes H2C[double bond, length as m-dash]CHRfn (Rfn = (CF2)n-1CF3; n = 8, 10) undergo the Mizoroki-Heck reaction with a variety of aromatic monobromides and polybromides such as 1,3- and 1,4-C6H4Br2, 1,3,5-C6H3Br3, 1,3,5-C6H3Br2Cl, 1,4-XC6H4Br (X = CF3, Rf8, COCH3, CN, 1,4-OC6H4Br), 1,2-O2NC6H4Br, 5-bromoisoquinoline, 5-bromopyrimidine, 3-bromo-5-methoxypyridine, and 3,5-dibromopyridine (sixteen examples, 78% average isolated yield). Typically, 1.2-2.4 equiv. of alkene are employed per Ar-Br bond, together with Pd(OAc)2 catalyst (4-5 mol%/Ar-Br bond), n-Bu4N+ Br- (0.8-1.0 equiv./Ar-Br bond), NaOAc (1.2-2.4 equiv./Ar-Br bond), and 3 : 1 w/w DMF/THF as solvent (120 °C). No effort is necessary to exclude air or moisture, and reactions may be conducted on >10 g scales. Only E isomers of the products Ar(CH[double bond, length as m-dash]CHRfn)m are detected. Thirteen representative examples are hydrogenated (Pd/C, balloon pressure H2), giving Ar(CH2CH2Rfn)m (92% average isolated yield).

Synthesis of ferrocene-labeled steroids via copper-catalyzed azide-alkyne cycloaddition. Reactivity difference between 2ß-, 6ß- and 16ß-azido-androstanes.

Copper-catalyzed cycloaddition of steroidal azides and ferrocenyl-alkynes were found to be an efficient methodology for the synthesis of ferrocene-labeled steroids. At the same time, a great difference between the reactivity of 2ß- or 16ß-azido-androstanes and a sterically hindered 6ß-azido steroid toward both ferrocenyl-alkynes and simple alkynes, such as phenylacetylene, 1-octyne, propargyl acetate and methyl propiolate, was observed.

Synthesis of steroid-ferrocene conjugates of steroidal 17-carboxamides via a palladium-catalyzed aminocarbonylation--copper-catalyzed azide-alkyne cycloaddition reaction sequence.

Steroids with the 17-iodo-16-ene functionality were converted to ferrocene labeled steroidal 17-carboxamides via a two step reaction sequence. The first step involved the palladium-catalyzed aminocarbonylation of the alkenyl iodides with prop-2-yn-1-amine as the nucleophile in the presence of the Pd(OAc)(2)/PPh(3) catalyst system. In the second step, the product N-(prop-2-ynyl)-carboxamides underwent a facile azide-alkyne cycloaddition with ferrocenyl azides in the presence of CuSO(4)/sodium ascorbate to produce the steroid-ferrocene conjugates. The new compounds were obtained in good yield and were characterized by (1)H and (13)C NMR, IR, MS and elemental analysis.