Sewage sludge processing determines its impact on soil microbial community structure and function

Composting and thermal drying are amongst the most commonly used post-digestion processes for allowing sanitation and biological stabilization of sewage sludge from municipal treatment plants, and making it suitable as soil conditioner for use in agriculture. To assess the impact of sludge-derived materials on soil microbial properties, fresh (LAF), composted (LAC) and thermally dried (LAT) sludge fractions, each resulting from a different post-treatment process of a same aerobically digested sewage sludge, were added at 1% (w/w) application rate on two contrasting (a loam and a loamy sand) soils and incubated under laboratory conditions for 28 days. Soil respiration, microbial ATP content, hydrolytic activities and arginine ammonification rate were monitored throughout the incubation period. Results showed that soil biochemical variables, including the metabolic quotient (qCO₂), were markedly stimulated after sludge application, and the magnitude of this stimulatory effect was dependent on sludge type (precisely LAT > LAF > LAC), but not on soil type. This effect was related to the content of stable organic matter, which was lower in LAT. Genetic fingerprinting by PCR–DGGE revealed that compositional shifts of soil bacterial and, at greater extent, actinobacterial communities were responsive to the amendment with a differing sludge fraction. The observed time-dependent changes in the DGGE profiles of amended soils reflected the microbial turnover dependent on the sludge nutrient input, whereas no indications of adverse effects of sludge-borne contaminants were noted. Our findings indicate that composting rather thermal drying can represent a more appropriate post-digestion process to make sewage sludge suitable for use as soil conditioner in agriculture.     

高粱光敏色素A基因的克隆、蛋白结构与长短日照诱导表达模式

光敏色素是一类红光/远红光受体,对植物光形态建成、外部形态和生理功能等方面起着重要的调节作用。为明晰光敏色素A在调控高粱光形态建成发育过程中的作用,本研究比较分析光温敏感程度不同的高粱品种Btx623、Rio、Tx430和LH645的PhyA基因序列和PHYA蛋白的保守结构域,利用qRT-PCR明确长短日照条件处理下PhyA基因的表达模式。结果表明,Btx623、Rio和Tx430之间PhyA基因序列存在非同义突变,LH645在PhyA基因的第7个外显子上插入了5 bp碱基序列;高粱PhyA蛋白中含有1个PAS-2结构域、1个GAF结构域、1个Phytochrome结构域、2个PAS结构域、1个组氨酸激酶A结构域和1个类似组氨酸激酶的ATP激酶结构;遗传进化树分析表明,单子叶和双子叶植物PhyA蛋白明显聚为2大类,高粱PhyA、谷子PhyA和玉米PhyA1、PhyA2聚为一个亚类,相互间亲缘关系较近,与水稻PhyA同源性相对较远;在短日照(SD)条件下各时期PhyA基因转录水平变化显著,Rio PhyA基因转录水平较Btx623和Tx430变化明显,LH645 PhyA基因转录变化不显著,在长日照(LD)条件下Rio PhyA基因转录水平低于Btx623和Tx430,LH645 PhyA基因转录水平变化不显著。以上结果表明,PhyA受光周期诱导,推测其在高粱光形态建成中起重要调控作用。本研究为进一步解析PhyA基因功能及其在调控高粱光形态建成发育过程中的作用提供理论基础。     

半干旱草甸草地不同处理下植被特征与土壤酶活性的变化

不同草地处理措施对植被和土壤会产生重要的影响。为探究不同草地处理措施对草甸草地的影响,以科尔沁草甸草地不同点为研究对象,设置围封（UNM）、围封+刈割（M）、围封+火烧（F）、放牧（G）4种处理,针对生长季土壤脲酶（S-UE）、碱性磷酸酶（S-AKP）、蔗糖酶（S-SC）活性和植被特征等开展研究,以探究草甸草地的最佳处理方式。结果显示：1）土壤酶活性随着土层深度的增加而降低,不同处理间的差异随着土层深度增加逐渐降低。2）放牧较围封处理,不同点植被高度、盖度、地上生物量和酶活性均降低,而丰富度指数增加。3）刈割较围封处理,不同功能群物种的补偿能力不同,禾本科的补偿能力大于菊科。4）火烧较围封处理,不同点植被高度、盖度、地上生物量、丰富度指数和3种水解酶活性均增加。5）多年刈割较放牧处理,植被高度、盖度和地上生物量和蔗糖酶、碱性磷酸酶活性均增加,丰富度指数和土壤脲酶活性均降低。综上所述,控制性火烧是半干旱地区草甸草地的最佳处理方式。     

Energy Assessement for Procedure Rationality of Recycling Materials from Wastes

The mathematical relationship for assessing total energy consumption within a material life cycle is presented in this paper. According to the relationship,the procedure rationality of recycling waste may be assessed quantitatively.     

Effect of drying on soil strength and corn emergence

Summary Laboratory studies were conducted to evaluate the effects of drying on soil strength and corn emergence (Zea mays L.). Corn was germinated in Billings silty clay under a bank of heat lamps which operated 9, 14, 19, or 24 h per day. Soil strength (modules of rupture), soil moisture content and emergence were measured daily.The relationship of soil strength to corn seedling emergence as influenced by the four light and heat durations and bare and mulched soil surfaces was determined. As soil strength increased emergence decreased until it ceased at soil strengths of about 80 kPa. Strength of this soil had a high negative correlation with soil water content and increased with time. Mulching decreased initial rate of drying, decreased crust strength, and improved corn emergence. The 14-hour light and heat treatment resulted in the highest corn emergence.Contribution from Colorado State Experiment Station, USDA-ARS Snake River Conservation Research Center, and USDA-ARS Fort Collins, respectively     

氮肥施用对柑橘果园土壤有机碳矿化的影响

土壤有机碳矿化是土壤向大气释放CO2的最大净输出途径,其与植被的净初级生产力的差值是判断生态系统碳“源”或“汇”的关键。采用室内模拟试验,在10、20、30℃ 3个温度条件下,研究施肥施用对柑橘果园土壤有机碳矿化的影响。结果表明：3种温度处理下,各施氮处理土壤有机碳矿化速率都表现为培养前期快速下降,培养后期保持相对稳定的趋势。在整个培养过程中,3种温度条件下各施氮处理的土壤CO2累积排放量为1328.25~2219.42 mg/kg,100 mg/kg（N4）处理土壤有机碳矿化量最大,CK处理最低,100 mg/kg（N4）和80 mg/kg（N3）2个高氮处理显著高于低氮50 mg/kg（N2）、30 mg/kg（N1）处理。土壤有机碳矿化速率随温度升高而增长,不同的土壤施氮条件下土壤有机碳矿化的温度敏感性不同,N2处理土壤有机碳矿化的温度敏感性最低,N4处理最高。柑橘果园土壤有机碳矿化受高施氮量影响较大,低施氮影响不明显。随着施氮量的增加土壤有机碳矿化的温度敏感性增加,氮肥施用和温度的共同作用可能使柑橘林向大气中排放的CO2增加。     

半根供铁对苹果砧木幼苗生长的影响

利用分根技术在水培条件下研究了半根供铁对苹果砧木幼苗生长的影响。结果表明,一半根系供铁不仅未影响植株对铁营养的需求,甚至在处理初期植株的铁吸收总量和铁吸收速率还略有提高。一半根系供铁苹果砧木小金海堂和山定子叶片活性铁质量分数均未降低,而且与对照相比无叶片黄化的现象。因此,通过半根供铁的方式来改善苹果砧木幼苗的生长,为进一步研究砧木缺铁适应性反应的调控部位打下基础,也为今后缺铁的矫正和提高铁素利用效率提供了一条新的思路。     

Hormetic UV-C seed treatments for the control of tomato diseases

Hormesis is a dose response phenomenon in which low, non-damaging doses of a stressor bring about a positive response in the organism undergoing treatment. Evidence is provided here that hormetic UV-C treatments of tomato seed can control disease caused by Botrytis cinerea, Fusarium oxysporum f. sp. lycopersici (FOL) and f. sp. radicis-lycopersici (FORL) on tomato (Solanum lycopersicum). Treating seeds with a 4 kJ m⁻² dose of UV-C significantly reduced both the disease incidence and progression of B. cinerea, with approximately 10% reductions in both on cv. Shirley. Disease severity assays for FOL and FORL on cv. Moneymaker showed dose-dependent responses: UV-C treatments of 4 and 6 kJ m⁻² significantly reduced the disease severity scores of FOL, whilst only the 6 kJ m⁻² showed significant reductions for FORL. To determine the effects of treatment on germination and seedling growth, UV-C doses of 4, 8 and 12 kJ m⁻² were performed on cv. Shirley. No negative impacts on germination or seedling growth were observed for any of the treatments. However, the 8 kJ m⁻² treatment showed significant biostimulation, with increases in seedling, root and hypocotyl dry weight of 11.4%, 23.1% and 12.0%, respectively, when compared to the control. Furthermore, significant increases in the root-mass fraction (10.6%) and root:shoot ratio (13.1%) along with a decrease in shoot-mass fraction (2.0%) indicates that the 8 kJ m⁻² treatment stimulated root growth to the greatest extent. There was no effect on hypocotyl and primary root length or the number of lateral roots, indicating no adverse effects to basic root architecture or seedling growth.     

Earthworm biomass response to soil management in semi-arid tropical Alfisol agroecosystems

Earthworms recorded during 1989–1993 across 15 soil management treatments, comprising three different tillagexthree organic amendments (bare, farmyard manure, and rice straw) and six perennial ley treatments, belonged to two endogeic species, Octochaetona phillotti (Michaelsen) and Lampito mauritii Kinberg, while in a nearby undisturbed natural revegetation area three species were found, including the above two and Octonochaeta rosea (Stephenson). The earthworm biomass showed significant temporal and spatial variations and was higher during the post monsoon period than in the early rainy season. No worm biomass was recorded during the dry season. In the tillage and organic amendment treatments, the biomass was drastically reduced from September 1989 to September 1991 after the application of carbofuran and some herbicides, and was significantly reduced during these two years compared to that of 1992. The maximum monthly earthworm biomass ranged between 2.5 and 17.9 g m^-2 across the treatments and increased several-fold in the nearby natural revegetation area (75.9 g m^-2). It significantly increased in perennial ley treatments compared to annual treatments with organic amendments. Thus the earthworm biomass varied significantly (P<0.01) across the 15 treatments, indicating discernible effects of soil management.Visiting Scientist (under the Rockefeller Foundation Environmental Research Fellowship in International Agriculture)