Some aspects on the nature of humic acid

For the extraction of humic acid from soils, solutions of sodium hydroxide or neutral sodium salts of inorganic and organic acids such as sodium fluoride, sodium oxalate and sodium pyrophosphate have been used most generally.     

Source of soil protease based on the splitting sites of a polypeptide

Abstract

Soil protease is an important enzyme in the nitrogen cycle which plays an essential role in the growth of various crops. We have attempted to identify a microbial source of soil protease. Selective soil incubation using antibiotics was suitable for a rough estimation of the groups of microorganisms responsible for the production of soil protease (Hayano and Watanabe 1990; Hayano 1993). Enumeration of proteolytic microorganisms in the field and analysis of their protease-producing ability enabled to evaluate the potential of various soil microorganisms for soil protease production (Watanabe and Hayano 1993a; Watanabe et al. 1994). For the accurate estimation of the soil protease source, the characteristics of the soil protease and microbial protease must be compared directly based on enzymatic properties as indices.     

Tetracycline resistance genes persist in soil amended with cattle feces independently from chlortetracycline selection pressure

Antibiotic residues and antibiotic resistance genes originating from animal waste represent environmental pollutants with possible human health consequences. In this study, we addressed the question whether chlortetracycline (CTC) residues in soils can act as selective pressure enhancing the persistence of tetracycline (TC-r) resistance genes in grassland soils receiving cattle feces. We performed a soil microcosm experiment, using 3 grassland soils with different management history, which were incubated with feces from conventionally raised dairy cows. The microcosms included treatments with a low dose (0.2 mg kg⁻¹), a high dose (100 mg kg⁻¹) and no CTC. The presence and abundance of TC-r genes tet(O), tet(Q) and tet(W) and the intI1 gene coding for class 1 integrase were assessed with real-time PCR after 0, 14, 28, 56 and 86 d of incubation. The genes tet(Q) and intI1 persisted in all feces-containing treatments for at least 28 d, and tet(W) and tet(O) for at least 86 d, though they went close to limits of quantification after 14–28 d in most cases. The soil, but not the dose of CTC, significantly affected the gene persistence. Concluding, certain TC-r genes originating from cattle feces may persist in soil for several months independently from antibiotic selection pressure.     

京郊畜禽粪污氮磷含量特征及影响因素分析

中国规模化养殖废弃物中养分资源数量可观,但缺乏循环利用技术,处置不当易引发环境污染问题。该文通过问卷调研和粪污样品检测,对京郊典型养殖场粪便和废水中的总氮、总磷含量特点进行分析,同时追踪典型规模化猪场废水中总氮、总磷含量变化的影响因素及其季节性变化特征。结果表明:所调研的养殖场中,猪粪、牛粪的总氮质量分数平均值分别为29.1,17.8 g/kg,总磷质量分数平均值分别为15.1,6.8 g/kg,猪粪便的总氮、总磷含量变异程度大于牛粪;猪场和牛场中废水总氮、总磷质量分数的平均值分别为892,540和82.4,53.3 mg/L,猪场废水总氮、总磷含量变异程度明显大于牛场。规模化猪场粪便总氮、总磷含量受到饲料配方的影响较大;受饲料和圈舍用水量的影响,现行饲养工艺及粪污处理方式下粪便对废水中总氮、总磷含量的影响较小;万头以上的规模化猪场废水中总氮、总磷含量存在季节性差异,且随着废水存储时间的推移其无机磷比例增加。这些变化特征可对畜禽粪便和养殖废水的资源化再利用提供了有用的参考。     

液体地膜覆盖对棉花产量与土壤环境的影响

基于棉田可持续发展的思想,研究了液体地膜覆盖对棉花产量与土壤物理性状的影响。结果表明,适量液体地膜(112.5 kg/hm²)覆盖棉花增产显著,平均增产皮棉21.7%。液体地膜覆盖棉田提高土壤温度和含水量,降低土壤容重。表明液体地膜覆盖棉田对土壤环境无不良影响,利用液体地膜覆盖棉田是一项可行的技术。     

Phosphorus sorption capacities and saturation of soils in two regions with different livestock densities in northwest Germany

Abstract. Soils in areas with high livestock density contribute to the eutrophication of aquatic ecosystems through loss of nutrients, especially phosphorus (P). In order to identify the potential for P loss from such soils we determined phosphorus extracted by water (H₂O-P), by double lactate (DL-P), and P sorption capacity (PSC) and degree of P saturation (DPS) in soil samples from two counties, one with low (Harle-catchment) and the other with very high livestock density (Vechta). Both catchments are hydrologically connected with the tidal areas of the North Sea.
The mean concentrations of H₂O-P (0.4mmol/kg) and DL-P (3.9 mmol/kg) were lower in the Harle-catchment than in the Vechta area (1.2 mmol/kg, 6.8mmol/kg). Although oxalate-extractable Al (Al_ox) and Fe (Fe_ox) and the derived PSCs varied according to soil type and to land use, the livestock density and the resulting high concentrations of oxalate-extractable P (P_ox) were shown to be the main reason for the very high DPS of up to 179% in the county of Vechta. These values exceeded DPS reported from other intensive pig feeding areas in western Europe and indicate the potential for significant P loss. Less than 40% of the variation in P_ox could be explained by the routinely determined H₂O-Por DL-P. Geostatistical analyses indicated that the spatial variability of P_ox depended on manurial history of fields and Al_ox, showed still smaller-scale variability. These were the major constraints for regional assessments of P losses and eutrophication risk from agricultural soils using available soil P-test values, digital maps and geostatistical methods.     

固体磷肥和液体磷肥对石灰性土壤不同形态无机磷及磷肥肥效影响的研究

土壤磷固定是影响石灰性磷肥肥效的主要原因。本文在田间滴灌条件下采用连续浸提的方法对液体磷肥和固体颗粒磷肥及其不同施用方法对石灰性土壤各形态无机磷含量动态变化的影响进行了研究,并比较了不同处理下加工番茄磷素营养效应。结果表明:各施肥处理0—20 cm土层Ca2-P和Ca8-P含量随施肥时间明显下降,而Ca10-P含量则显著上升,表明磷肥在石灰性土壤中不断向Ca10-P转化并被固定。液体磷肥追肥处理0—20 cm土层Ca2-P含量在各时期均显著高于其他施肥处理(P＜0.05),且液体磷肥追肥可以明显保持土壤0—20 cm土层较高的Ca8-P含量。与其他施肥处理相比,液体磷肥追施可减少石灰性土壤对磷的固定,增加0—20 cm土层Ca2-P和Ca8-P含量(P＜0.05),显著提高土壤磷的有效性。液体磷肥追施处理可显著提高加工番茄叶片含磷量和经济产量(91725 kg/hm2)。与传统过磷酸钙颗粒磷肥作基肥处理（CK1）相比,液体肥料全做追肥可使加工番茄经济产量提高26.7%,并明显提高了磷肥利用率。在滴灌条件下石灰性土壤上液体磷肥分次追施比传统的固体颗粒磷肥基施具有明显的优势,是一种非常具有应用前景的施肥方式。     

Distribution of exogenous phytase activity in soil solid–liquid phases and their effect on soil organic P hydrolysis

The bioavailability and stability of organic phosphorus (P) in the soil may be affected by exogenous phytase (EPase) activity and distribution, but remain poorly understood. The distribution of EPase activity and hydrolysis ability of EPase on organic P in soil solid‐liquid phases was investigated. The EPase addition to soil suspension (1:20, w/v) from three soil types (red soil, brown soil, and cinnamon soil) under three treatments (untreated soil, removing clay from soil, and removing organic matter from soil) with different characters in the solution and solid phases was assayed. The results showed that the disappearance pattern of EPase activity from solution was similar for all soils, whereas the enzyme activity on the solid phase was dependent on soil types and treatments with the greatest in red soil and untreated soil. When EPase was added to soils, the adsorption ratio of organic matter and clay was 10 to 25% and 3 to 7%, respectively, with sorption capacity of organic matter being significantly (p < 0.05) stronger than that of clay. Additionally, soil dehydrogenase activity, which is the indicator of overall soil microbial activities, increased after EPase addition and the two enzymes showed significant negative relation in the soil suspension and solution. At the same time, the organic P decreased significantly (p < 0.05) after the addition of EPase in the soil solid, which had a varied rate under –40% after incubating 192 h, whereas organic P in the solution phase increased significantly (p < 0.05). This study demonstrated that organic matter had a strong protective and adsorptive effect on EPase effectiveness and microbes mightbe directly affect EPase longevity and decay. This finding suggests that EPase activity in the solid phase played a more important role in organic P hydrolysis.     

Effects of different application timings of methane fermentation digested liquid to paddy plots on soil nitrogen and rice yield

Treatment of animal and food wastes using a methane fermentation technique is drawing considerable public attention as a suitable option for the utilization of biomass resources. The application of a fermentation byproduct (methane fermentation digested liquid) as an agricultural fertilizer has been investigated. Determining the appropriate timing required for applying digested liquid on a rice (Oryza sativa L.) paddy plot is important. The concentrations of soil nitrogen (N) components and rice yield should be considered because digested liquid contains both inorganic and organic N. This study compares the N transformation and the rice yield and growth at different application times over a period of 3 y. The effects of the timing of basal application on soil N were different and the timing that maximized the rice yield was different in each year. Days before ponding (DBP) affected soil N before mid-summer drainage, and rice growth rates at the panicle formation stage and the ear emergence stage. The effects of DBP disappeared before harvest. The results indicated that sufficient potentially mineralizable N existed regardless of DBP, and the effect of DBP lessened after the mid-summer drainage, which coincides with the period when N uptake is most active.     

稻田土壤养分空间变异与合理取样数研究

以嘉善县陶庄农场内一块0.52hm2的水稻田为研究区,采用地统计方法和常规统计方法进行土壤pH及养分(全氮、全碳、速效钾、速效磷、速效镁、速效锰、速效铜、速效锌)的空间变异及其合理取样数目研究。结果表明,各土壤养分在田间尺度均存在一定的空间变异,全氮、全碳、速效钾、速效磷等主要养分的空间格局呈南北向条带状,与农户经营田块的方向基本一致;不同农户耕种、管理下的4田块的土壤养分差异显著;反映土壤肥力的土壤全碳、全氮等养分的合理取样数目在95%的置信度和5%的相对误差条件下为45～个,基本上每个农户经营田块为1个,即可反映土壤养分的真实情况。因此,试验区以N素管理为主的精确田间管理的土壤采样可以采用以农户经营地块为单位的混合样采样方式,以减少土壤采样量和分析成本。     

温度和水分对不同肥料条件下黑土磷形态转化的影响及机制

采用室内微宇宙试验法,研究了温度（25℃和10℃）、土壤湿度（湿度分别为最大持水量的50%和25%,即50% WHC和25%WHC）对不同肥料条件下黑土磷素形态转化及土壤磷酸酶活性的影响。结果表明,土壤温度和水分及其交互作用对不同肥料条件下土壤磷形态转化以及土壤酶活性有显著影响。土壤温度（25℃）和土壤湿度（50% WHC）显著增加了土壤有效磷、Ca2-P、Ca8-P的含量,而土壤有机磷含量显著降低;在土壤中添加氮磷钾肥料后,这种作用变得尤为明显。高的土壤温度（25℃）和合适的土壤湿度（25%WHC）能够显著提高土壤磷酸酶的活性。土壤磷酸酶活性与土壤有效磷含量均呈显著正相关,表明可以通过提高土壤温度和保持土壤合适的湿度来提高土壤磷酸酶,活化和提高土壤磷的有效性,进而促进土壤磷释放。     

沼肥对保护地土壤酶及其呼吸强度的影响

以等有机质含量的猪粪、沼渣为基肥,追肥(化肥与沼液)以等N、等P、等K进行施用,采用二裂式区组设计的方法研究了沼肥、猪粪、化肥等不同施肥组合对保护地土壤酶活性及其呼吸强度的影响。结果表明,未施任何肥料的对照处理,其土壤磷酸酶、过氧化氢酶活性和土壤呼吸强度最弱。沼渣与沼液配合施用较沼渣与化肥配合施用有利于提高土壤磷酸酶的活性,而施用猪粪或沼渣、施用沼液或化肥对土壤磷酸酶活性的影响差异较小;施肥对土壤过氧化氢酶活性影响较小;施有机肥或有机肥和化肥配施提高了土壤呼吸强度。施用化肥、沼渣分别比施用沼液、猪粪有利于提高土壤呼吸强度。猪粪、沼渣与化肥配合施用分别比与沼液配合施用的土壤呼吸强度高。     

畜禽有机肥氮、磷在红壤中的矿化特征研究

选用腐熟的猪粪、鸡粪和第四纪红土发育的典型红壤为试验材料,通过室内培养试验,研究了土壤中矿质氮(NO-3-N和NH4+-N)及Olsen-p的动态变化.结果表明,有机肥中氮和磷的矿化具有不同特征.氮在红壤中的矿化阶段为:前4周缓慢释放,矿化速率为N 0.29～0.46mg/(kg·d);4～10周快速释放,矿化速率为N...     

不同水分处理下液膜覆盖对夏玉米生长及产量的影响

针对塑料地膜对农业生产造成的严重污染问题,运用对照处理方法,探讨了液体地膜覆盖对夏玉米生长发育及产量等方面的影响。结果表明,液膜覆盖使夏玉米株高和茎粗均比对照偏大,其中,低水分处理下差异最为显著。夏玉米叶面积指数低水分处理时液膜覆盖在生育前期较对照偏大,生育后期偏小;而中、高水分下液膜覆盖叶面积指数在整个生育期内均比对照偏大。液膜覆盖使夏玉米光合速率和蒸腾速率显著增大,有利于光合产物的形成。低水分处理下液膜覆盖增产效果最好,增产率达到56.97%,产投比为1.695,高水分下液膜覆盖增产效果最差,增产率仅为15.57%,液膜覆盖产投比小于对照。研究认为,夏玉米液膜覆盖能有效抵抗干旱逆境从而达到节水增产的显著效果。     

作物茬口对连作棉田土壤环境及棉花产量的影响

于2007－2008年在连作8 a的棉田上进行不同作物轮作倒茬田间试验,以研究不同茬口对连作棉田土壤养分、土壤微生物区系以及棉花产量的影响,从而筛选出适宜棉田轮作倒茬的最佳作物茬口。研究结果表明：不同作物茬口的土壤有机质、速效养分含量及棉花产量均高于连作棉田,其中加工番茄茬口对土壤的速效磷含量增加最为显著,小麦、玉米茬口对土壤速效钾含量增加显著;各作物茬口土壤微生物总量均比连作棉田有明显的增加,表现为细菌和放线菌数量增加真菌减少;草木樨、番茄茬口土壤氨化细菌、硝化细菌生理群也明显增加。不同作物茬口的棉花产量表现为加工番茄→棉花＞草木樨→棉花＞小麦→棉花＞玉米→棉花＞棉花→棉花;加工番茄、玉米、小麦可作为连作棉田的良好前茬。     

磷肥在潮褐土中动态转化及其影响因素的研究

利用培养及微区试验研究P肥施用潮褐土后的动态转化及其影响因素表明,施肥初期土壤中除难溶性Ca10-P外,各无机P组分均有不同程度地提高,随着时间的延续各组分间的相互转化呈一定规律。种植作物直接影响P肥动态转化的方向。     

Cyanobacteria in alkaline soil and the effect of cyanobacteria inoculation with pyrite amendments on their reclamation

The succession of cyanobacteria was studied in a usar (alfisol, solonetz, alkaline) soil, located in a tropical region of upper Gangetic plain, following the first rainfall for a period of 10 months (i.e., July–April). A dozen cyanobacteria were identified to grow on the soil surface and their appearance was in the following order: Microcoleus sp., Calothrix brevissima, Scytonema sp., Cylindrosprmum licheniformae, Cylindrosprmum fertilissima, Nostoc calcicola, Nostoc punctiformae, Aphanothece parietina, Nostoc commune, Aulosira fertilissima, Phormidium sp., and Oscillatoria sp. Among these cyanobacteria, N. calcicola was the dominant species. N. calcicola was inoculated on the alkaline soil and incubated under ambient conditions in the light for 2 years in the laboratory. Changes in soil properties were more rapid after the incorporation of pyrite (FeS₂). Recovery was monitored by using a filamentous heterocystous cyanobacterium N. calcicola and its bicarbonate-resistant (HCO₃^–R) mutant. The mutant strain showed better response to modification of soil pH following growth in soil.     

Effects of soil temperature and anaerobiosis on degradation of biodegradable plastics in soil and their degrading microorganisms

The bioplastic PHB/HV (copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate) underwent a faster degradation at 30°C than at 52°C in soil under aerobic conditions, while there was no remarkable difference between 30°C and 52°C in the degradation rate of PCL [poly(ε-caprolactone)], PBSA (polybutylene succinate and agipate), and PBS (polybutylene succinate). PHB showed the fastest degree of degradation among the four plastics at 30°C and PBSA the fastest at 52°C. Degradation of all the four plastics was nor observed both at 30°C and 52°C under anaerobic conditions for 50 d. Microorganisms on the degrading plastics appeared to be diverse at 30"C, including bacteria and fungi. However, among the several to ca. 10 kinds of bacterial and fungal strains isolated from the degradation sites of each plastic at 30°C, only one or two fungal strains were able to degrade the respective plastics in vitro. The degraders were identified as Mucor sp. (PHB), Paecilomyces sp. (PCL), Aspergillus sp. (PBSA), and Cunninghamella sp. (PBSA). In contrast, only a single type of fungus was observed at the degradation sites of PCL and PBSA at 52°C. The fungus isolated from PCL and PBSA was identified as Thermomyces sp. This study demonstrated that soil temperature and anaerobiosis exerted significant effects on the degradation of the plastics, and that fungi were mainly responsible for the degradation of the plastics in soil.