[Effects of combined application of biochar with organic amendments on enzyme activity and microbial metabolic function of carbon sources in infertile red soil]. / ç”Ÿç‰©è´¨ç‚­é æ–½æœ‰æœºç‰©æ–™å¯¹è´«ç˜ çº¢å£¤é ¶æ´»æ€§å’Œå¾®ç”Ÿç‰©ç¢³æºä»£è°¢åŠŸèƒ½çš„å½±å“.

To improve carbon (C) sequestration and soil fertility of red soil, a two-year (2017 and 2018) field experiment was conducted to investigate the effects of two organic amendments (i.e., corn straw and sheep manure) applied alone or combined with biochar on soil nutrient content, enzyme activities involved in C cycling, and microbial substrate utilization rate in infertile red soil. There were six treatments, including control (non-amendment), corn straw, sheep manure and across biochar treatments (without and with biochar amendment, respectively). The organic amendments and biochar were applied in 2017 and 2018. The results showed that, compared with the control, organic amendments significantly increased soil pH, organic C, total nitrogen, available phosphorus and potassium contents. Compared with straw and manure alone, the biochar co-application with straw or manure significantly increased the contents of soil organic C, available potassium, and available nitrogen, without any significant interactive effects. Application of organic amendments significantly increased the activities of soil ß-glucosidase (BG), cellobiohydrolase (CB), ß-xylosidase (XYL), and peroxidase (PERO). The combined application of biochar and straw significantly reduced the activity of phenol oxidase (PHOX) by 28.6% and PERO by 22.2% in comparison with straw addition alone, respectively, while the combined application of biochar and manure significantly reduced the activities of α-glucosidase (AG) by 46.1%, BG by 50.9%, XYL by 41.6%, and PERO by 31.3% compared with manure addition alone, respectively. Compared with the control, the application of organic amendments significantly enhanced soil basal respiration and microbial utilization rates of carbohydrates, whereas biochar co-application significantly decreased microbial utilization rates of carbohydrates and carboxylic acids. Microbial C source utilization rates were significantly and positively correlated with the activities of BG and PERO. Thus, biochar co-application with organic amendments can enhance nutrient content and reduce enzymatic and microbial metabolic activities, thereby may facilitate C sequestration and fertility of infertile red soil.

[Effects of Nitrogen Fertilizer Management on CH4 and N2O Emissions in Paddy Field].

Methane (CH4) and nitrous oxide (N2O) are two extremely important greenhouse gases in the atmosphere. Nitrogen fertilizer is an important factor affecting CH4 and N2O emissions in rice fields. Rational application of nitrogen fertilizer can not only promote high yields of rice but also reduce greenhouse gas emissions. Existing studies have shown that nitrogen reduction and optimal application can effectively improve the nitrogen use efficiency of rice on the basis of ensuring the yield and reduce the loss of N2O caused by nitrification and denitrification of excessive nitrogen in soil. Fertilization times and fertilizer types have significant effects on CH4 and N2O emissions in paddy fields. In this study, a field experiment was conducted for two consecutive years (2019-2020) to study the effects of fertilizer application on CH4 and N2O emissions from rice fields by setting up four treatments consisting of no fertilizer (CK), customary fertilizer application by farmers (CF), twice fertilizer (TT), and 20% replacement of chemical fertilizer by organic fertilizer (OF) using static chamber-gas chromatography. Additionally, the effect of integrating rice yield and integrated global warming potential (GWP) on the greenhouse gas emission intensity (GHGI) per unit of rice yield was analyzed to explore fertilizer application for yield increase and emission reduction in a typical rice growing area in the middle and lower reaches of Yangtze River. The results showed that:① compared with those of CK, the fertilizer treatments reduced CH4 emissions by 14.6%-25.1% and increased N2O emissions by 610%-1836% in both years; ② compared with those of CF, both the TT and OF treatments showed a trend of increasing CH4 emissions and reducing N2O emissions. CH4 emissions increased by 1.8% (P>0.05) and 14.0% (P<0.05), respectively. The annual average of N2O emissions decreased by 63.3% (P<0.05) and 49.2% (P<0.05) in both the TT and OF treatments, respectively. ③ Compared with that of CK, both fertilizer applications increased rice yield and reduced GHGI; compared with that of CF, the OF and TT treatments increased the average annual rice yield by 17.0% and 10.7%, respectively, and reduced GHGI by 6.8% and 13.7%, respectively. The OF treatment had a better yield increase than that of the TT treatment, and the TT treatment had a slightly better emission reduction than that of the OF treatment. In terms of combined yield and GHG emission reduction, both twice fertilizer (TT) and 20% replacement of chemical fertilizer by organic fertilizer (OF) could reduce the intensity of GHG emission per unit of rice yield and achieve yield increase and emission reduction while ensuring rice yield.

[Effects of different fertilization regimes on soil fungal communities under Phyllostachys violascens stand]. / 不同施肥模式对雷竹林土壤真菌群落特征的影响.

In order to investigate the effect of fertilization on soil fungal community of Phyllostachys violascens stand, we characterized the abundance and community structure of soil fungi using the methods of terminal restriction fragment length polymorphism (T-RFLP) and real-time quantitative PCR. The experimental treatments included blank control (CK), chemical fertilizer (CF), organic manure (M), mixture of chemical fertilizer and organic manure (CFM) and mixture of chemical fertilizer and organic manure plus mulching (CFMM). The results showed that fungal community structure and diversity were markedly affected by different fertilization regimes. In 0-20 cm soil layer, CF and CFMM treatments resulted in a significant reduction of Shannon and evenness indices. Soil fungi under CK, M, CFMM treatments in 0-20 cm soil layer and CK, CF, CFMM treatments in 20-40 cm soil layer formed independent community structures. Soil fungal abundance showed significantly positive correlation with the concentrations of soil total nitrogen, ammonium nitrogen and nitrate nitrogen. Organic matter, ammonium nitrogen, available phosphorus and available nitrogen concentrations were the main factors that influenced the variation of fungal community composition. The above findings indicated that 0-20 cm and 20-40 cm soil layers had different characteristics in response to different fertilization regimes under P. violascens stand. The soil fungal community in the 0-20 cm layer was mainly affected by soil organic matter, while that in the 20-40 cm layer was sensitive to the input of chemical fertilizer. The effect of fertilization on the diversity of fungal community mainly occurred in the 0-20 cm soil layer.

[Effects of bamboo charcoal on the growth of Trifolium repens and soil bacterial community structure].

The effects of addition rates (0, 3% and 9%) and particle sizes (0.05, 0.05-1.0 and 1.0-2.0 mm) of bamboo charcoal on the growth of Trifolium repens and soil microbial community structure were investigated. The results showed that bamboo charcoal addition greatly promoted the early growth of T. repens, with the 9% charcoal addition rate being slightly better than the 3% charcoal addition rate. The effects of different particle sizes of bamboo charcoal on the growth of T. repens were not different significantly. Growth promotion declined with time during 120 days after sowing, and disappeared completely after 5 months. DGGE analysis of the bacterial 16S rDNA V3 fragment indicated that bamboo charcoal altered the soil bacterial community structure. The amount and Shannon diversity index of bacteria in the bamboo charcoal addition treatments increased compared with CK. The quantitative analysis showed that the amount of bacteria in the treatment with bamboo charcoal of fine particle (D < 0.05 mm) at the 9% addition rate was significantly higher than in the other treatments. The fine bamboo charcoal had a great effect on soil bacteria amount compared with the charcoal of other sizes at the same addition rate.