不同施肥模式对赤红壤旱地作物产量和土壤肥力的影响

采用长期定位田间试验,研究不同施肥模式对赤红壤旱地花生一甘薯轮作制产量和土壤肥力的影响.5年定位试验表明,平衡施肥平均产量最高,花生和甘薯比常规施肥增产13.1％～13.5％,净增收提高14.0％;氮磷钾对花生和甘薯的增产率逐年提高,但花生和甘薯分别对缺磷和缺钾较敏感.年际间产量变化趋势表明,常规施肥对花生和甘薯产量的变异系数大于平衡施肥;不施肥区和氮磷钾缺素区的产量均呈现逐年下降,但缺氮对花生产量的敏感性大于甘薯,甘薯缺磷或缺钾对产量的敏感性高于花生.平衡施肥的氮磷钾利用率平均分别为40.9％、17.7％和24.2％;缺素区的土壤供肥量比不施肥区提高了近1倍;土壤有机质都有所提高,施用氮肥都使土壤酸度有所增加;不施肥区和氮磷钾缺素区都使相应的土壤速效养分明显下降;常规施肥使土壤有效磷下降22.5％,碱解氮和速效钾则基本维持不变,但平衡施肥使土壤有效磷含量基本不变,碱解氮和速效钾则分别提高26.2％和38.4％.     

Pipes and pipe flow process in an upland catchment,Wales

The results of observations on the spatial localisation, origin and function of soil pipes in an upland catchment are discussed. The pipes occur in distinct zones in the brown earth soils of the lower slopes, and form a hydrological link conducting water between an upslope zone of highly permeable skeletal soils and the stream channel. It is proposed that in this catchment, pipes develop from an initial network of mole burrows, modified by hydraulic activity to produce an efficient downslope transmission network. A conceptual model for the pipe slope segment is proposed which recognises the importance of this transmission role. Slope discharge controls switching between saturated throughflow, pipe flow and overland flow, each of which has a specific threshold value for operation. Attempts to investigate the significance of pipe flow at the catchment scale met with limited success, but it appears to be important in increasing both contributing area and duration of storm flow.     

Organic phosphorus in upland soil

The nature and behaviour of soil organic phosphorus has been studied in many places of the world, especially in Iowa, U.S.A., and Quebec, Canada.     

长期施肥对旱地红壤微生物和酶活性的影响

以中国科学院鹰潭红壤生态试验站长期有机肥与无机肥处理的旱地红壤为研究对象,探讨了长期不同施肥处理对土壤中可培养微生物数量、土壤微生物生物量碳(SMBC)及脲酶、酸性磷酸酶、过氧化氢酶、脱氢酶和转化酶等5种土壤酶活性的影响。结果表明,长期施厩肥处理能显著提高土壤有机质含量及SMBC,增加土壤真菌的数量和土壤酶活性。无机肥NK(缺P)处理下微生物数量、SMBC和5种土壤酶活性均显著降低,说明磷元素对维持土壤良好的生化环境至关重要,是供试土壤样点中最主要的限制性营养元素。相关性分析表明,各种土壤酶活性之间均呈显著或极显著正相关; 酶活性与土壤有机质、SMBC和真菌数量之间呈显著或极显著正相关,表明土壤酶活性能够有效地反映旱地红壤在长期施肥条件下土壤质量的变化。     

施加氮磷肥对希腊北部高原草地上土壤pH与植被生产力的相互关系的影响

The potential role of soil pH in modulating plant productivity was assessed on the basis of dry mass, harvested in the form of 0.25 m2 quadrats, in two low-productivity upland grasslands of northern Greece subjected to annual factorial nitrogen (N) and phosphorus (P) fertilization (15 g N m-2 year-1 and 10 g P m-2 year-1) over a minimum period of 3 years. It was hypothesized that under these particular conditions, a positive relationship would exist between soil pH and plant productivity and, further, that N or P fertilizer application of a nutrient limited system, would result in a weakening of this positive relationship. A significant positive relationship was confirmed between soil pH and plant productivity in one of the two study areas and a positive trend in the other. Moreover, plant productivity increase, following fertilization, appeared to have a detrimental effect on the soil pH-plant productivity relationship. Findings support the original hypotheses and strengthen the idea that plant diversity-mediated soil pH-plant productivity relationships are a result of the more intense plant speciation that occurred under the more "typical" soil conditions of higher pH in temperate as opposed to tropical regions.     

土壤水流模式染色剂示踪及优先流程度评估

优先流是结构性土壤水分入渗的主要方式。为了直接利用土壤水流模式分析其优先流程度,该文采用亮蓝染色剂示踪原状与扰动土柱的土壤水运移,定量评估优先流的相对发育程度。研究结果表明原状土柱优先流发育,空间变异性强,受优先流通道的特征控制,其优先流水流模式以蚯蚓大孔隙流和土块裂隙优先流为主。扰动土柱的水流模式为活塞流,无优先流发育。该文提出了随深度变化的染色面积比的变异系数指示原状土柱优先流相对程度的评价准则:变异系数越低,优先流程度越高。变异系数≥0.5%为优先流程度一般发育,0.25%~0.5%之间为发育,≤0.25%为非常发育。并通过原状和扰动土柱灌溉模拟试验验证了评价准则的可靠性。     

Simulation of flow patterns and ion-exchange in soil percolation experiments

An increased understanding of ion-exchange processes in raw-humus was obtained by simulations using quantitative mathematical models. The work is based on a series of percolation experiments with a water flow of about 1 mm min^?1 through raw-humus samples of 4 cm thickness. For the input solutions consisting of 10^?3 N H₂SO₄, HNO₃, HCl and NaCl the results indicate that cation-exchange reactions are the most important processes for the chemical composition of the run-off. Since a large part of the water flows quickly through the soil, both the water residence time and the ion-exchange kinetics must be taken into account. As a basis for the chemical model, a hydrologic sub-model reproducing the residence time distribution of the flow in the soil is used. Considering the ions H⁺, M⁺ (monovalent metal ions) and M²⁺ (divalent metal ions), four different chemical models were tried but only one of them gave satisfactory agreement with the experimental results. This model has 5 independent parameters and consists of first and second order chemical processes.     

Water flow paths in soil control element exports in an Andean tropical montane forest

We tested the hypothesis that concentrations of chemical constituents in stream water can be explained by the depth of water flow through soil. Therefore, we measured the concentrations of total organic carbon (TOC), NO₃‐N, NH₄‐N, dissolved organic nitrogen (DON), P, S, K, Ca, Mg, Na, Al and Mn in rainfall, throughfall, stemflow, litter leachate, mineral soil solution and stream water of three 8–13 ha catchments on steep slopes (1900–2200 m above sea level) of the south Ecuadorian Andes, from April 1998 to April 2003. Peak C (14–22 mg litre^?1), N (0.6–0.9 mg litre^?1), K (0.5–0.7 mg litre^?1), Ca (0.6–1.0 mg litre^?1), Mg (0.3–0.5 mg litre^?1), Al (110–390 μg litre^?1) and Mn (3.9–8.4 μg litre^?1) concentrations in stream water were associated with lateral flow (fast near‐surface flow in saturated topsoil) while the greatest P (0.1–0.3 mg litre^?1), S (0.3–0.7 mg litre^?1) and Na (3.0–6.0 mg litre^?1) concentrations occurred during low baseflow conditions. All elements had greater concentrations in the organic layer than in the mineral soil, but only C, N, K, Ca, Mg, Al and Mn were flushed out during lateral‐flow conditions. Phosphorus, S and Na, in contrast, were mainly released by weathering and (re‐)oxidation of sulphides in the subsoil. Baseflow accounted for 32% to 61% of P export, while > 50% of S was exported during intermediate flow conditions (i.e. lateral flow at the depth of several tens of cm in the mineral soil). Near‐surface water flow through C‐ and nutrient‐rich topsoil during rainstorms was the major export pathway for C, N, Al and Mn (contributing > 50% to the total export of these elements). Near‐surface flow also accounted for one‐third of total base metal export. Our results demonstrate that near‐surface flow related to storm events markedly affects the cycling of many nutrients in steep tropical montane forests.     

Comparison of field techniques for sampling soil solution in an upland peatland

Abstract. Results from recent studies of peatland biogeochemistry suggest that appropriate soil water sampling techniques are required in order to advance our understanding of peatland soil systems. In a comparative field experiment, concentrations of inorganic solutes and dissolved organic carbon (DOC) were measured in soil water extracted at a depth of 10 cm beneath the surface of deep peat by three techniques: zero-tension (z-t) lysimeters, PTFE suction samplers, and polysulfone suction samplers. The majority of solute concentrations were broadly similar, but mean concentrations of silicon, DOC, iron and aluminium in water extracted by z-t lysimeters and PTFE samplers were in ratios of 1:5; 1:2; 1:5 and 1:3 respectively. Mean conductivity and concentrations of chloride and hydrogen ion were significantly larger in the z-t lysimeter samples, which had sodium, potassium and magnesium to chloride ratios that were very similar to local rainfall. The z-t lysimeters appeared to sample macropores preferentially, while the suction samplers collected micropore water.     

In-canopy throughfall measurements in Norway spruce: Water flow and consequences for ion fluxes

Canopy throughfall was collected in funnels equipped with tipping buckets. The funnels were installed at 4 distances from the tree trunk and at 6 depths in the canopy of a Norway spruce forest at Klosterhede, Denmark. The throughfall water flux was registered during individual rain events. The smallest quantity of throughfall was sampled closest to the tree trunk, and the largest quantity of throughfall was sampled in the periphery of the canopy at all levels in the canopy. The quantity of throughfall was highest at the top of the tree and decreased down through the canopy. The intensity of the water flow decreased through the canopy which brought the throughfall water in contact with the foliage for longer periods in the lower canopy than in the upper canopy. The higher wettability caused a larger leaching of especially potassium in the lower canopy. Differences in rain intensity did not influence the distribution and the pattern of water flow in the canopy.     

Changes in soil profile characteristics through cultivation of an upland Vertisol in Zambia

Abstract. Crops grown on virgin upland Vertisols of Zambia, are reported to perform rather poorly. However, subsoiling followed by repeated cultivation over two years apparently improves crop growth. Highest yields were recorded under long-term cultivation (12 years). To evaluate the reasons for these differences in crop response to Vertisol management, physical and hydrodynamic characteristics of soil profiles were studied in three soil management systems. The management systems were: uncultivated or virgin land; land cultivated for two years; and land cultivated for 12 years. The mean soil aggregate size decreased with increased time of cultivation, mostly due to the decrease of the largest sized aggregates. The surface horizon dried more slowly on the long-term cultivation plot. A comparison of the hydraulic conductivities indicated that water intake in the deeper layers improved with increased period in cultivation. Oxygen diffusion measurements showed good aeration at field capacity, to a depth of 0.32m on the long-term cultivation plots, but only to 0.17 m and 0.25 m for 2 years cultivation and virgin plots respectively. Repeated cultivation was beneficial in improving surface soil tilth and in improving subsurface drainage, thus removing the problem of a perched water table which occurred close to the soil surface under natural conditions.     

The forms and availability to plants of soil potassium as related to mineralogy for upland Oxisols and Ultisols from Thailand

Potassium (K) deficiency is widespread in crops on highly weathered upland soils under a tropical monsoonal climate. Critical assessment of the forms of K in soils and of the ability of soils to release K for plant uptake is important for the proper management of K in crop production. The relationships between different pools of K were investigated as a function of silt and clay mineralogy for 14 upland Oxisols and 26 upland Ultisols soils from Thailand. Most soils contained no K-minerals in the silt fraction. XRD showed that kaolinite is the dominant clay mineral with variously minor or moderate amounts of illite, hydroxy-Al interlayered vermiculite and smectite present in some soils. For some soils, both conventional and synchrotron XRD were unable to detect illite. Analytical TEM including EFTEM of individual clay crystals showed that clay in the apparently illite-free samples contained very small amounts of illite. Many kaolinite particles appear to contain K which may be present in illite interleaved with kaolinite crystals. A glasshouse K-depletion experiment was conducted to assess the K supply capacity and changes in chemical forms of K and K-minerals using exhaustive K depletion by Guinea grass (Panicum maximum). Potassium deficiency symptoms and mortality of plants occurred on light textured soils, whereas plants survived for six harvests for Oxisols with clay texture, relatively high CEC and higher NH₄OAc-K (exchangeable K plus water-soluble K). There is a strong linear relationship of unit slope between NH₄OAc-K and cumulative K uptake by plants indicating that NH₄OAc-K is a major form of K available to plants. Thus K-bearing minerals contributed little K to plants over the time scale of the experiment and XRD patterns of whole soil samples, silt and clay from soils after cropping mostly showed no change from those for the initial soil. An exception was for a single surface soil clay where a minor amount of smectite was formed from illite by K release to plants.     

The impact of sludge amendment on methanogen community structure in an upland soil

In the EU, municipal sewage sludge application to agricultural land has increased dramatically since the ban on dumping at sea came into effect in 1998. There are many concerns related to potential contamination and reduction in plant productivity. In this study, the aim was to assess the impact of repeated long-term soil amendment with anaerobically digested sewage sludge on methanogen diversity in an upland soil ecosystem. Sludge-treated and untreated upland soil samples as well as samples of the sludge used, were analysed for the diversity of methanogens using TGGE, PCR-RFLP and DNA sequence analysis of approximately 490 bp of the mcrA operon. PCR analysis using mcrA specific oligonucleotide primers confirmed the presence of methanogen DNA in treated and untreated soil samples and in sewage sludge. TGGE was used to describe the diversity of methanogen mcrA sequences and the differences in community structure between samples. Ninety-six mcrA gene PCR products were screened using RFLP analysis representing methanogen DNA amplified from anaerobically digested sewage sludge, control soils and sludge treated soils. Fourteen RFP's were detected in all treatments, five of which were common to all three treatments. Thirty-eight cloned amplimers were selected for sequencing and phylogenetic analysis. These included representatives of each RFP. From control soils, sludge and sludged soil samples 15, 16 and 7 clones were sequenced, respectively. Phylogenetic analysis suggested that they represented hitherto uncharacterised mcr genes; 35 of the clones fell into 7 clusters supported by moderate to high bootstrap values. The diversity of methanogens in an upland soil (treated and untreated) and sludge was evaluated and marked differences in the diversity of the methanogen communities was observed between the treatments. Our results indicate that sludge application may reduce soil methanogen community diversity.     

Long-term fertilization effects on active ammonia oxidizers in an acidic upland soil in China

The effects of long-term fertilization of acidic soils on ammonia-oxidizing archaea (AOA) and bacteria (AOB) communities and its ecological implications remain poorly understood. We chose an acidic upland soil site under long-term (27-year) fertilization to investigate ammonia oxidizer communities under four different regimes: mineral N fertilizer (N), mineral NPK fertilizer (NPK), organic manure (OM) and an unfertilized control (CK). Soil net nitrification rates were significantly higher in OM soils than in CK, N or NPK soils. Quantitative analysis of the distribution of amoA genes by DNA-based stable isotope probing revealed that AOA dominate in CK, N and NPK soils, while AOB dominate in OM soils. Denaturing gradient gel electrophoresis and clone library analyses of amoA genes revealed that Group 1.1a-associated AOA (also referred to as Nitrosotalea) were the most dominant active AOA population (>92%), while Nitrosospira Cluster 3 and Cluster 9 were predominant among active AOB communities. The functional diversity of active ammonia oxidizers in acidic soils is affected by long-term fertilization practices, and the responses of active ammonia oxidizers to mineral fertilizer and organic manure are clearly different. Our results provide strong evidence that AOA are more highly adapted to growth at low pH and low substrate availability than AOB, and they suggest that the niche differentiation and metabolic diversity of ammonia oxidizers in acidic soils are more complex than previously thought.     

Monitoring soil restoration in an open-pit mine in northern Italy

Mining causes significant damage to the environment: the removal of top layers of soil causes loss of structure and functionality, with a subsequent reduction in biodiversity. Soil communities are important for soil formation, they contribute to the improvement of several characteristics of soils and they play key roles in many processes that enhance the success of restoration. Unfortunately, soil fauna are poorly monitored even though they represent a good tool for assessing soil quality. The “La Speranza” quarry in northern Italy was studied from the start of the restoration process in 2008 until 2012. Six sites were selected and monitored annually. Microarthropods were extracted from three replicates of soil drawn from each site, identified to order level and then counted. Both the abundances of taxa and the soil biological indices applied (Shannon diversity index (H’), Pielou's evenness index (J), the Acari to Collembola ratio (A/C) and the QBS-ar index) revealed a good level of soil recovery over the years studied. Furthermore, the edaphic organisms that are generally associated with stable conditions in the soil (e.g. Symphyla, Protura, Chilopoda), appeared in the most recent of the years.     

Loss of pesticides from a litchi orchard to an adjacent stream in northern Thailand

In the hill country of northern Thailand use of agrochemicals is increasing steadily and contaminating streams and groundwater. We have measured pesticide leached from a litchi orchard to an adjacent stream and identified the flow components contributing to the pesticide transport after installing two discharge measurement stations with automatic water samplers in the stream. For 2 years, between June and September, we applied methomyl, and in 1 year additionally chlorothalonil, to the 2‐ha orchard and monitored water fluxes and pesticide concentrations in the stream water. Pesticide loads ranged from 1.6 to 3% of mass applied for chlorothalonil, a strongly sorbing fungicide, and 6.4–11.4% for the more weakly sorbing insecticide methomyl. Directly after application, pesticide transport was dominated by a fast flow component, reaching the flume before the discharge peak. Later, pesticides were transported mainly by preferential interflow, which peaked about 30 hours after a rain event. The groundwater pathway was not found to contribute to pesticide loss. Antecedent rain conditions proved to be important for the pesticide transport behaviour. While at the beginning of the rainy season large falls of rain did not lead to pesticide contamination, at the end of the season pesticide transport was induced by as little as 0.1 mm of rain. The occurrence of preferential interflow means that the hilly regions in northern Thailand are highly susceptible to contamination by pesticides used by farmers.     

Spatial patterns of top soil carbon sensitivity to climate variables in northern Chinese grasslands

Abstract

Estimation of the sensitivity for soil organic carbon to climate change is critical for evaluating the potential response of the terrestrial biosphere to global change. In this study, we integrated CENTURY 4.5 model with GIS to assess the soil organic carbon sensitivity to climate variable shifting and atmospheric carbon dioxide enrichment in northern Chinese grasslands. The response of top soil (0–20 cm) organic carbon to climate change depended on the relative sensitivity of net primary productivity and soil respiration. A 4°C increase in soil temperature led to a loss of 4.7% of soil organic carbon in the Alpine Meadow region, but the same temperature increase led to a maximum loss of only 2.3% of soil organic carbon in the Temperate Steppe region. The effects of precipitation changes on soil organic carbon were varied depending on the moisture level of the local grassland system. The direct effect of carbon dioxide enrichment was to reduce carbon loss throughout northern Chinese grasslands, especially in droughty regions. Alpine Meadow was the most sensitive region under climate change, and it will become the biggest potential carbon source in Chinese grasslands as climate warming continues to occur. Increased atmospheric carbon dioxide concentrations led to net carbon sequestration in all grasslands and tended to diminish the carbon loss driven by precipitation and temperature changes.     

The transition from arable lands to rubber tree plantations in northern Thailand impacts weed assemblages and soil physical properties

In South‐East Asia, rapid land use changes in recent decades have raised concerns for biodiversity and soil conservation. Weeds provide many ecosystemic services for soil protection and support biodiversity, and could mitigate the negative effects of intensification. We investigated the changes in weed assemblages and weed–soil interactions on a chronosequence from annual crops to mature rubber tree plantations. We sampled five fields for each of four land uses in mountainous northern Thailand (rainfed upland rice, maize, young rubber tree (RT ) intercropped with maize, and mature RT ). We characterized weed assemblages (abundance, richness) and soil properties (bulk density, water, carbon and nitrogen content). Rice had the most diverse and abundant weed assemblages. Weed assemblages differed between (i) rice, (ii) maize and young RT with maize and (iii) mature RT . Soil water content was the highest in mature RT . Other soil properties varied strongly within and among fields, and did not vary significantly among land uses. Water and nitrogen content increased overall with living soil cover but decreased with weed species richness in mature RT . Such interactions could provide a basis for sustainable weeding practices favourable to soil and biodiversity conservation.