Nitrogen fertilization is essential for achieving high rice yields and is widely practiced in rice cultivation. There is an ongoing discussion on the possible effects of N application on CH 4 emission from rice fields. CH 4 emission is a net consequence of CH 4 production, oxidation and transport from the soil in which the CH 4 is produced to the atmosphere, and the interactions among these processes. Nitrogen influences all the processes of CH 4 emission from rice fields either directly or indirectly and the effects are either negative or positive at the ecosystem, microbial and biochemical level. Because of this complexity and counter-balance among the effects, it is difficult to assess the net N effect on CH 4 emissions from rice fields on a national or global scale. Field measurements also show a contradiction in that positive, negative and no effects of N application on CH 4 emissions have been observed. Nevertheless, it is clear that the effect of N application on CH 4 emission is N-form dependent. Nitrate-based fertilizers are able to mitigate CH 4 emission, but they are rarely applied to rice fields and generally not practicable to mitigate CH 4 emission because of their low use efficiency and stimulatory effect on N 2 O emission. In contrast, the application of organic N stimulates CH 4 emission because additional organic carbon is supplied for CH 4 production. However, it is not sufficient to conclude that CH 4 emission intensity would have been decreased by the replacement of organic N, which dominated traditional rice cultivations, with chemical N fertilizers, which are used in current rice cultivations, because the fertilizer replacement has also enhanced rice yields, which in turn affects CH 4 production, oxidation and transport. Establishing quantitative relationships between N status in soil and CH 4 production, oxidation and transport is essential to assess the effects of chemical N fertilizer application on CH 4 emissions from rice fields.

Over time, the relative effects of elevated [CO 2 ] on the aboveground photosynthesis, growth and development of rice (Oryza sativa L.) are likely to be changed with increasing duration of CO 2 exposure, but the resultant effects on rice belowground responses remain to be evaluated. To investigate the impacts of elevated [CO 2 ] on seasonal changes in root growth, morphology and physiology of rice, a free-air CO 2 enrichment (FACE) experiment was performed at Wuxi, Jiangsu, China, in 2002-2003. A japonica cultivar with large panicle was exposed to two [CO 2 ] (ambient [CO 2 ], 370 lmol mol À1 ; elevated [CO 2 ], 570 lmol mol À1 ) at three levels of nitrogen (N): low (LN, 15 g N m À2 ), medium (MN, 25 g N m À2 ) and high N (HN, 35 g N m À2 ). Elevated [CO 2 ] increased cumulative root volume, root dry weight, adventitious root length and adventitious root number at all developmental stages by 25-71%, which was mainly associated with increased root growth rate during early growth period (EGP) and lower rate of root senescence during late growth period (LGP), while a slight inhibition of root growth rate occurred during middle growth period (MGP). For individual adventitious roots, elevated [CO 2 ] increased average length, volume, diameter and dry weight early in the season, but the effects gradually disappeared in subsequent stages. Total surface area and active adsorption area per unit root dry weight reached their maxima 10 days earlier in FACE vs. ambient plants, but both of them together with root oxidation ability per unit root dry weight declined with elevated [CO 2 ] during MGP and LGP, the decline being larger during MGP than LGP. The CO 2 -induced decreases in specific root activities during MGP and LGP were associated with a larger amount of root accumulation during EGP and lower N concentration and higher C/N ratio in roots during MGP and LGP in FACE vs. ambient plants. The results suggest that most of the CO 2 -induced increases in shoot growth of rice are similarly associated with increased root growth.

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Concerns regarding the detrimental effects of burning crop residues on human health and the environment have increased interest in alternative uses of crop residues. We examined the in situ use of crop residue as a source of supplemental N for succeeding crops in rice (Oryza sativa L.)‐based cropping systems at three sites during 3 yr. The experiments included a rice–wheat (Triticum aestivum L.) rotation at Yixing, Jiangsu Province, China; a rice–wheat rotation at Ludhiana, Punjab, India; and double‐rice cropping at Taojiang, Hunan Province, China. The supply of N from crop residues was assessed in the absence of fertilizer N as the difference in total plant N between plots with and without residue. At Yixing, incorporation of wheat residue before rice significantly increased the N supply to the rice by 14 kg N ha−1 averaged across 3 yr. At Ludhiana, incorporation of rice residue before wheat reduced the N supply by 3 kg N ha−1 to the wheat, but increased the N supply by 5 kg N ha−1 to the rice crop following the wheat. In all cases, the return of crop residues had no net benefit on crop yield when fertilizer N was supplied at rates sufficient to eliminate N deficiency. The incorporation of crop residues did not increase the N supply to the succeeding crop during its vegetative growth phase, but the N supply to the crop at later growth stages was often increased. Adjustments in the timing and rate of fertilizer N are probably necessary to optimally supply N to crops receiving residues.

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Purpose We examined the effects of vermicompost application as a basal fertilizer on the properties of a sandy loam soil used for growing cucumbers under continuous cropping conditions when compared to inorganic or organic fertilizers. Materials and methods A commercial cucumber (Cucumis sativus L.) variety was grown on sandy loam soil under four soil amendment conditions: inorganic compound fertilizer (750 kg/ha,), replacement of 150 kg/ha of inorganic compound fertilizer with 3000 kg/ha of organic fertilizer or vermicompost, and untreated control. Experiments were conducted in a greenhouse for 4 years, and continuous planting resulted in seven cucumber crops. The yield and quality of cucumber fruits, basic physical and chemical properties of soil, soil nutrient characteristics, and the soil fungal community structure were measured and evaluated. Results and discussion Continuous cucumber cropping decreased soil pH and increased electrical conductivity. However, application of vermicompost significantly improved several soil characteristics and induced a significant change in the rhizosphere soil fungal community compared to the other treatments. Notably, the vermicompost amendments resulted in an increase in the relative abundance of Ascomycota, Chytridiomycota, Sordariomycetes, Eurotiomycetes, and Saccharomycetes, and a decrease in Glomeromycota, Zygomycota, Dothideomycetes, Agaricomycetes, and Incertae sedis. Compared to the organic fertilizer treatment, vermicompost amendment increased the relative abundance of beneficial fungi and decreased those of pathogenic fungi. Cucumber fruit yield decreased yearly under continuous cropping conditions, but both inorganic and organic fertilizer amendments increased yields. Vermicompost amendment maintained higher fruit yield and quality under continuous cropping conditions. Conclusions Continuous cropping decreased cucumber yield in a greenhouse, but basic fertilizer amendment reduced this decline. Moreover, basal fertilizer amendment decreased beneficial and pathogenic fungi, and the use of vermicompost amendment in the basic fertilizer had a positive effect on the health of the soil fungal community.

Pd catalysts supported on TiO 2 with different crystalline phases were prepared with formaldehyde as reducing agent and examined for hydrodeoxygenation (HDO) of guaiacol. Their properties were characterized by N 2 adsorption, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. Compared to the carbon-supported Pd catalysts, TiO 2 -supported Pd catalysts exhibited higher C−O bond scission ability, which may be attributed to the presence of partially reduced titanium species originating from the reduction of Ti 4+ by spillover hydrogen from Pd at 200 °C on the surface of TiO 2 . Guaiacol was hydrogenated on Pd sites to give 2-methoxycyclohexanol, which diffused to partially reduced titanium species and subsequently reacted with hydrogen from Pd to generate cyclohexane. Anatase TiO 2 -supported Pd catalyst gave the highest HDO activity of guaiacol among the Pd catalysts supported on three types of TiO 2 (anatase, rutile, and their mix, P25), suggesting that more partially reduced titanium species are in favor of the HDO reaction because anatase is facile to reduce by H 2 at 200 °C. Higher selectivity of cyclohexane for Pd/TiO 2 reduced at 500 °C than that reduced at 200 °C further confirmed that the enhanced C−O bond scission ability of Pd/TiO 2 is mainly attributed to the partially reduced titanium species on the surface of TiO 2 .

The fast pace of cropland loss in China is causing alarm over food security and China's ability to remain selfreliant in crop production. Mudflats after organic amendment can be an important alternative cropland in China. Land application of sewage sludge has become a popular organic amendment to croplands in many countries. Nevertheless, the land application of sludge to mudflats has received little attention. Therefore, the objective of the present work was to investigate the impact of sewage sludge amendment (SSA) at 0, 30, 75, 150 and 300 t ha −1 rates on soil physicochemical properties, perennial ryegrass (Lolium perenne L.) growth and heavy metal accumulation in mudflat soil. The results showed that the application of sewage sludge increased organic matter (OM) content by 3.5-fold while reducing salinity by 76.3% at the 300 t ha −1 rate as compared to unamended soil. The SSA reduced pH, electric conductivity (EC) and bulk density in mudflat soil, increased porosity, cation exchange capacity (CEC) and contents of nitrogen (N), phosphorus (P), exchangeable potassium ions (K + ), sodium ions (Na + ), calcium ions (Ca 2+ ) and magnesium ions (Mg 2+ ) in comparison to unamended soil. There were 98.0, 146.6, 291.4 and 429.2% increases in fresh weight and 92.5, 132.4, 258.6 and 418.9% increases in dry weight of perennial ryegrass at 30, 75, 150, and 300 t ha −1 , respectively, relative to unamended soil. The SSA increased metal concentrations of aboveground and root parts of perennial ryegrass (p < 0.05). The metal concentrations in perennial ryegrass were Zn > Cr > Mn > Cu > Cd > Ni, and the metal concentrations in roots were significantly higher than aboveground parts. The metal accumulation in perennial ryegrass correlated positively with sludge application rates and available metal concentrations in mudflat soil. Land application of sewage sludge was proved to be an effective soil amendment that improved soil fertility and promoted perennial ryegrass growth in mudflat soil. However, heavy metal accumulation in plants may cause food safety concern.