Cyanide in paper de‐inking sludge used as a soil amendment

Paper de‐inking sludge is processed during the recycling of paper, and is sometimes used as a soil amendment. In this study the effect of a compost application on the cyanide (CN) status in soils of a public park was investigated. The compost was a mixture of chipped limbs and paper de‐inking sludge. Furthermore, the cyanide solubility was studied by conducting batch experiments with different pH levels. Total cyanide in the amended soils ranged from 540 to 740 mg CN kg^—1, and water soluble cyanide from 170 to 370 μg CN l^—1 as determined by means of an aqueous extract. Easily‐liberatable cyanides, which include the toxic free cyanide (HCN and CN^—) and weak metal‐cyanide complexes, were not present in the soil. From this result and the fact that iron blue pigments are used during paper printing, it can be inferred that cyanides occurring here were exclusively stable iron‐cyanide complexes [Fe(CN)₆]. With increasing pH the solubility of cyanide increased. In contrast to soils of coking plants, in which cyanide occur as Berlin blue, Fe₄[Fe(CN)₆]₃, the cyanide solubility in the paper de‐inking sludge amended soils was substantially lower, especially in the neutral and alkaline range. Thus, cyanides in paper de‐inking sludge could be present as sparingly soluble metal‐cyanide compounds with the general formula A₂B[Fe^II(CN)₆] with A = K⁺, Na⁺ and B = Ca²⁺ or divalent transition metals and B₂[Fe^II(CN)₆] with B = divalent transition metals. Pollution exposure by the pathways soil → human, and soil → air → human can be neglected. However, since leaching of iron‐cyanide complexes into the ground water cannot be excluded, and since they are decomposed to HCN when exposed to day light, environmental hazards by the pathway soil → ground water → surface water are possible. This is the risk arising from paper de‐inking sludge applications to soils.     

Effect of organic matier application and water regimes on the transformation of fertilizer nitrogen in a Philippine soil

Greenhouse experiments using the tracer technique showed that about 20 per cent of the fertilizer nitrogen added as basal to the Maahas clay soil wa11 immobilized in submerged soils to which no organic material was added. The addition of organic matter to the soil increases the amount of nitrogen immobilized and the magnitude depends on the carbon to nitrogen ratio of the materials added. More fertilizer nitrogen waa immobilized in the soils under upland and alternate wet-and-dry conditions than under submerged soil conditions.

The uptake of fertilizer nitrogen by rice plants growing under submerged soil conditions ceased at the vegetative stage of growth because only a small amou11t of available nitrogen remains in the soil at this time, but the rice plant continued to absorb gradually untagged nitrogen from the soil throughout the reproductive etages of growth.

Losses of fertilizer nitrogen were great under the alternate wet-and-dry conditions (submerged-upland). The loss of nitrogen from the soli-plant system was reduced by the addition of dee straw, which also reduced the uptake of fertilizer nitrogen but not the total dry matter production under the experimental conditions. Fertilizer nitrogen immobilized during the first crop remained mostly in the soil throughout the full period of the second crop.

The total nitrogen uptake by rice plants was not affected by the soil moisture tension under the upland conaltlons used in the study but the movement of nitrogen from the leaves to the panicles during the reproductive etage seemed to decrease as the soil moisture tension increased.     

适宜灌水施氮方式利于玉米根系生长提高产量

为研究不同灌水方式和施氮方式对玉米根系生长分布的影响,2011年在大田条件下采用垄植沟灌技术,设交替灌水、固定灌水、均匀灌水和交替施氮、固定施氮、均匀施氮2因素3水平的随机完全组合试验方案。分抽雄期、灌浆期和成熟期对0~100 cm土层监测植株正下方、植株正南侧和植株正北侧的根系生长状况。结果表明,灌水方式对各位置根长及根系总量影响均达显著水平,施氮方式只对植株南侧根长和根系总干质量影响显著,二者的交互作用只对植株北侧根长和总根长影响显著。交替灌水均匀施氮在监测时期内维持了较大总根长,并使得灌浆期植株不同位置根长、总根量(总根干质量除外)均较大,并最终获得较大的产量(11 524 kg/hm2)。而固定灌水固定施氮总根长最小,产量最低。各处理下0~40 cm土层根长所占整个土层根长比例均较高,该比值以交替灌水均匀施氮最大。对比发现,根系生长分布对灌水方式更加敏感,通过不同灌水与施氮调控玉米根系生长分布应集中在0~40 cm土层,交替灌水均匀施氮最有利于根系的生长和产量的提高,为垄植沟灌下较好的灌水施氮方式。该研究为通过不同灌水施氮方式调控作物根系生长并获得高产提供了一定理论依据。     

半干旱区玉米水肥空间耦合效应Ⅱ.土壤水分和速效氮的动态分布

在灌水量为300m3/hm2、施N肥量为248.1kg/hm2的条件下,模拟大田条件研究了两种水肥空间耦合方式下的土壤水分、速效N的动态运移规律。试验表明,在半干旱地区隔沟灌溉水肥异区、隔沟灌溉水肥同区两种处理方式的灌溉水在剖面上均以垂直运动为主,同时存在水平运动。隔沟灌溉水肥同区处理的速效N在剖面上垂直运动明显,处理后15天速效N基本均匀地分布于0~100cm土层内,速效N含量在施肥区和未施肥区之间差异较小;而隔沟灌溉水肥异区处理的速效N垂直运动程度小,速效N主要分布在60cm以上土层,速效N水平运动不明显,施肥区速效N含量远高于未施肥区。水肥异区养分的淋溶深度较小,淋失的可能性小,有利于养分长期在剖面较浅层次中分布,为作物吸收创造了条件。     

Soil–root cross‐talking: The role of humic substances

The biological activity of humic substances (HS) has been elucidated in the last 40 years. Growth enhancement from HS has been demonstrated in several plants in the laboratory and the field. Morphogenesis effects have also been investigated and include induction of lateral root formation and root hair initiation in intact plants and stimulation of root and shoot development in treated cell calluses. HS enhance nutrient use efficiency, aiding assimilation of both macro and microelements and promoting plant growth by the induction of carbon, nitrogen, and secondary metabolism. The review aims are to: (1) shed light on the mechanism by which plants “talk” with soil through humic substances, (2) elucidate the plant responses to the stimulatory effects of HS, the regulatory circuits that allow plants to cope with humus, and the feedback between plant community structures, and (3) show (in light of recent debate about the alkaline extraction of soil humic substances) the plant capability to acquire biologically active substances from soil. It will be shown that plants modify soils, creating and maintaining favorable habitats for growth and survival. Therefore, organic substances exuded by roots are not a wasteful loss of carbon and energy. They represent an evolved strategy by which plants “talk” to the soil. The mobilization of bioactive organic/humic substances from bulk soil or bulk humus is critical to plant and soil health.     

Nitrogen forms affect root growth,photosynthesis, and yield of tomato under alternate partial root‐zone irrigation

To increase efficiency of water and nitrogen (N) fertilizer use, this study was conducted with a split‐root pot experiment to investigate the effects of different forms of N fertilizer on root growth, photosynthesis, instantaneous water use efficiency (IWUE), and yield of tomato (Lycopersicon esculentum L.) under alternate partial root‐zone irrigation (APRI). Three irrigation modes comprised conventional irrigation (CI) and two kinds of APRI, i.e., APRI with water content in the drying soil compartment controlled at ≥ 60% or 40% of the water‐holding capacity (APRI‐60, APRI‐40). Two N forms included ammonium‐N and nitrate‐N supplied as calcium nitrate or ammonium sulfate, respectively. The results show that APRI‐60 enhanced root growth and increased leaf IWUE with a slight yield reduction compared with CI regardless of the N form supplied. In contrast, APRI‐40 significantly decreased root growth and inhibited photosynthesis, thereby resulting in a significant yield loss. In addition, at the flowering stage tomato plants grew better with ammonium‐N than nitrate‐N supply; however, at the fruit expansion stage and maturity stage, the tomato plants had a higher biomass accumulation and yield with nitrate‐N than ammonium‐N supply. Therefore, the application of APRI should consider the soil water condition coupled with an appropriate N form. In the present study, APRI controlled at ≥ 60% of the water‐holding capacity (WHC) for the drying soil side with nitrate‐N supply was the best water‐fertilizer supply for tomato cultivation.     

Nitrogen Fractions in Arable Soils in Relation to Nitrogen Mineralization and Plant Uptake

Abstract

Nitrogen (N) as a major constituent of all plants is one of the most important nutrients. Minimizing input of mineral nitrogen fertilizer is needed to avoid harm to the environment. Optimal input of mineral nitrogen should take the nitrogen supply of the soil into account. Many different soil tests have been proposed for determining soil nitrogen availability. In this article we present a new approach that is based on the measurement of nitrate, ammonium, and dissolved organic nitrogen (DON) in a 0.01 M CaCl₂ soil extract. Eighteen agricultural soils, differing widely in the availability of nitrogen were used, fertilized and unfertilized. It is shown that the nitrogen uptake by maize plants (Zea Mays L.) in both “N‐fertilized” and “N‐unfertilized” soils as measured in a pot experiment can be described with a simple model using the measured nitrogen fractions in the extract. The main source of nitrogen uptake by the plants is the mineralized organic nitrogen during the growing period. It is shown that the initial measured DON fraction is a good indicator of the nitrogen mineralized during plant growth.     

Soil‐ and plant‐based nitrogen‐fertilizer recommendations in arable farming

Under‐ as well as overfertilization with nitrogen (N) will result in economic loss for the farmer due to reduced yields and quality of the products. Also from an ecological perspective, it is important that the grower makes the correct decision on how much and when to apply N for a certain crop to minimize impacts on the environment. To aggravate the situation, N is a substance that is present in many compartments in different forms (nitrate, ammonium, organic N, etc.) in the soil‐plant environment and takes part in various processes (e.g., mineralization, immobilization, leaching, denitrification, etc.). Today, many N‐recommendation systems are mainly based on yield expectation. However, yields are not stable from year to year for a given field. Also the processes that determine the N supply from other sources than fertilizer are not predictable at the start of the growing season. Different methodological approaches are reviewed that have been introduced to improve N‐fertilizer recommendations for arable crops. Many soil‐based methods have been developed to measure soil mineral N (SMN) that is available for plants at a given sampling date. Soil sampling at the start of the growing period and analyzing for the amount of NO ‐N (and NH ‐N) is a widespread approach in Europe and North America. Based on data from field calibrations, the SMN pool is filled up with fertilizer N to a recommended amount. Depending on pre‐crop, use of organic manure, or soil characteristics, the recommendation might be modified (±10–50 kg N ha^–1). Another set of soil methods has been established to estimate the amount of N that is mineralized from soil organic matter, plant residues, and/or organic manure. From the huge range of methods proposed so far, simple mild extraction procedures have gained most interest, but introduction into practical recommendation schemes has been rather limited. Plant‐analytical procedures cover the whole range from quantitative laboratory analysis to semiquantitative “quick” tests carried out in the field. The main idea is that the plant itself is the best indicator for the N supply from any source within the growth period. In‐field methods like the nitrate plant sap/petiole test and chlorophyll measurements with hand‐held devices or via remote sensing are regarded as most promising, because with these methods an adequate adjustment of the N‐fertilizer application strategy within the season is feasible. Prerequisite is a fertilization strategy that is based on several N applications and not on a one‐go approach.     

Nutrient‐enriched soils and native N‐fixing plants in New Zealand

Approximately 40% of New Zealand's land mass is fertilized grassland with entirely non‐native plants, but currently there is substantially increased interest in restoration of native plants into contemporary agricultural matrices. Native vegetation is adapted to more acid and less fertile soils and their establishment and growth may be constrained by nutrient spillover from agricultural land. We investigated plant–soil interactions of native N‐fixing and early successional non N‐fixing plants in soils with variable fertility. The effects of soil amendments of urea (100 and 300 kg N ha^?1), lime (6000 kg CaCO₃ ha^?1), and superphosphate (470 kg ha^?1) and combinations of these treatments were evaluated in a glasshouse pot trial. Plant growth, soil pH, soil mineral N, Olsen P and nodule nitrogenase activity in N‐fixing plants were measured. Urea amendments to soil were not inhibitory to the growth of native N‐fixing plants at lower N application rates; two species responded positively to combinations of N, P and lime. Phosphate enrichment enhanced nodulation in N‐fixers, but nitrogen inhibited nodulation, reduced soil pH and provided higher nitrate concentrations in soil. The contribution of mineral N to soil from the 1‐year old N‐fixing plants was small, in amounts extrapolated to be 10–14 kg ha^?1 y^?1. Urea, applied both alone and in conjunction with other amendments, enhanced the growth of the non N‐fixing species, which exploited mineral N more efficiently; without N, application of lime and P had little effect or was detrimental. The results showed native N‐fixing plants can be embedded in agroecology systems without significant risk of further increasing soil fertility or enhancing nitrate leaching.     

Solubilization of iron by water‐extractable humic substances

The capability of water‐extractable humic substances (WEHS) to solubilize Fe from sparingly soluble Fe‐hydroxide was studied. Addition of WEHS (1.7 mmol organic C l^—1) to a dialysis tube containing labeled insoluble Fe‐hydroxide caused an increase in the amount of ⁵⁹Fe measured in the external solution. The humic fraction was also able to solubilize Fe from soil samples, with levels comparable to those obtained using a solution containing 100�μM DTPA. By measuring the amount of ⁵⁹Fe eluted from soil columns pre‐loaded with ⁵⁹Fe‐WEHS it was possible to evaluate the mobility of Fe complexed to the humic molecules. The recovery of ⁵⁹Fe varied from 2% to 25% in respect to the soil type used. The ability of Fe‐WEHS to serve as an Fe source for the phytosiderophore hydroxy‐mugineic acid (HMA) was also analyzed. The removal of ⁵⁹Fe from the Fe‐WEHS complex by HMA was demonstrated by adding the phytosiderophore to a dialysis tube containing the ⁵⁹Fe‐WEHS complex. The observations suggested a ligand exchange between the phytosiderophore and the humic fraction. The results indicate that WEHS is able to increase the amount of Fe present in the soil solution, possibly by forming mobile complexes with the micronutrient. These complexes could act as easily available Fe sources in Fe acquisition processes by both monocot and dicot plants, playing an important role particularly in soils with low available Fe.     

Impact of the rhizosphere on soil microarthropods in agroecosystems on the Georgia piedmont

We pulse-labeled corn (Zea mays) and weed plants with photosynthetically fixed Carbon-14 to investigate the importance of the rhizosphere as a food source for soil microarthropod food webs. In field samples, we followed the movement of ¹⁴C from plant shoots to roots to microarthropods. In conventionally tilled (CT) agroecosystems, the soil microarthropods accumulated radioactive tracer and reached concentrations as high as those in roots. In no-tillage (NT) agroecosystems, radioisotope concentrations in microarthropods were not as high. The CT systems lack surface organic litter, an alternate food base for microarthropods. Results suggest that feeding in the rhizosphere is more important in CT systems. Weeds transferred higher concentrations of tracer into the rhizosphere than did crop plants, suggesting that weeds in CT systems may be important in fueling food webs.     

Characterization of Compost Based on Crop Residues: Changes in Some Chemical and Physical Properties of the Soil after Applying the Compost as Organic Amendment

The objectives of the present study were to make a physical, physicochemical, and biological characterization of compost obtained from crop residues of horticultural plants grown in greenhouses and to assess the physical and chemical responses of a soil tested after the applications of this organic amendment. The compost showed a high percentage of inorganic material because the source of this compost includes not only crop residues but also soil; for this reason, it had high coarseness index (CI), electrical conductivity (EC), and pH. The application of the organic amendment to a soil with reduced bulk density (BD) increased the percentage of particles with large diameters, as well as increased the nutritional status and organic matter (OM). However, nitrogen and potassium levels in soil were low. Compost addition provoked an increase in soil EC, which restricts its use to salt-tolerant plants.     

Effect of the introduction of the nitrogen-fixing bacteria <Emphasis Type="Italic">Pseudomonas putida</Emphasis> 23 on the nitrogen balance in soil

The inoculation of red beets with the nitrogen-fixing bacteria Pseudomonas putida 23 increased the activity of the nitrogen fixation in the rhizosphere of the plants grown on meadow soil in the central part of the Oka River floodplain. The yield of the red beets and the uptake by plants of nitrogen from the soil and from the ¹⁵N-labeled nitrogen fertilizer applied on the trial microplot increased significantly. A statistically significant additional fixation of nitrogen from the atmosphere and a positive balance of nitrogen in the soil-plant system without significant changes in the bulk content of the soil nitrogen after the plant growing were found in a greenhouse experiment with the application of P. putida. It can be supposed that the excessive nitrogen determined in this system is related to the incorporation into plants of atmospheric nitrogen fixed in the rhizosphere of the inoculated plants. The application of P. putida 23 makes it possible to decrease the rates of NPK fertilizer by two times without losses in the yield of red beets.     

植被缓冲带在水源地面源污染治理中的作用

在山地丘陵区遭遇高强度降雨时,常常发生水土流失;水流携带泥沙下泄,过量施入农田的肥料、农药等化学物质随之进入河流、水库、湖泊等地表水和地下水水体,进而造成水体富营养化等面源污染,危害水源地安全。为梳理植被缓冲带能够控制水土流失、阻控污染物移动、解决水源地面源污染问题,明确该项技术措施减少和治理水源地面源污染的机制,为水源地面源污染防治和水环境改善提供参考。在概括介绍植被缓冲带的类型、功能的基础上,对该项技术措施减少和治理水源地面源污染的机制进行讨论。植被缓冲带治理水源地面源污染的机制主要有:①植物在生长过程中自身对氮磷等物质的吸收;②利用植被固结土壤,减少水土流失;③植被覆盖、拦蓄能够延长径流在地面的停留时间而增加水分入渗、减少氮磷等物质随地表径流流失;④植物根系参与土壤中多种物理、化学和生物过程,加速碳、氮、磷等物质的形态转化。针对水源地面源污染特点和植被缓冲带的建设技术及其应用要点,提出相关建议,并对今后该技术的发展进行了展望。     

Influence of water regime on growth,yield, and nitrogen uptake of rice

Abstract

Greenhouse and field experiments were conducted to study the effects of water regime on growth of rice. The greenhouse experiment investigated the effects of two water regimes‐continuous flooding and flooding with soil drying between crops for 2 to 3 weeks on the growth of rice during six cropping (for six week each) on seven soils varying widely in total N contents (0.07 to 0.35%). The results averaged for the 7 soils indicated that the drymatter production or N uptake of rice was not affected by the water regimes during the six croppings.

The field experiment conducted during the dry season for two consecutive years (1976 and 1977) on a near neutral clay soil studied the effects of three water regimes (continuous flooding alternate flooding and soil drying every 2 weeks, and continuous flooding with 2 weeks mid season soil drying after 6 weeks of transplanting) and three levels of fertilizer N (0, 100 and 200 kg N/ha as urea) on grain yield and N uptake of rice. The results confirmed the absence of any significant reduction in grain yield or N uptake as a result of any of the soil drying treatments during the growing season on the unfertilized plots carrying a rice crop. On the plots fertilized with 100 or 200 kg N/na, alternate flooding and drying resulted in a significant depression in both grain yield and N uptake. Soil analysis supported heavy losses of N in the fertilized plots that underwent alternate flooding and soil drying apparently by nitrification and denitrification reactions.

The results of this study suggest that alternate flooding and drying of soils in the presence of established rice plants itiay not cause a significant loss of nitrogen in unfertilized plots although in plots fertilized with high rates of N the losses may be large as indicated by the performance of rice crop.     

干湿交替灌溉与施氮耦合对水稻根际环境的影响

为了探讨不同水氮耦合对水稻根际土壤环境及根系分泌有机酸总量的影响,以新稻20号为材料,进行盆栽试验,设置浅水层、轻度(-20 k Pa)和重度干湿交替灌溉(-40 k Pa)3种灌溉方式及不施氮肥,中氮(normal nitrogen,MN,240 kg/hm~2)和高氮(high nitrogen,HN,360 kg/hm~2)3种氮肥水平9个处理。结果表明:轻度干湿交替灌溉及中氮增加了土壤酶活性,提高土壤中微生物数量,根系分泌有机酸总量显著提高(P0.05);重度干湿交替灌溉及重施氮肥则降低土壤酶活性及微生物的数量,显著(P0.05)减少根系分泌有机酸的总量;相关分析表明:根际土壤酶活性及微生物数量与不同生育期根系分泌有机酸总量呈显著(P0.05)或极显著(P0.01)的正相关关系。土壤酶活性、微生物数量及有机酸总量的供氮效应为正效应,轻度干湿交替灌溉供水效应及耦合效应均为正效应,而重度干湿交替灌溉的控水及耦合效应则为负效应。研究可为通过水氮耦合调控水稻良好的根际环境提供依据。     

Heavy‐metal displacement in chelate‐treated soil with sludge during phytoremediation

Heavy metals (HMs) in domestic sewage sludge, applied to land, contaminate soils. Phytoremediation is the use of plants to clean‐up toxic HMs from soil. Chelating agents are added to soil to solubilize the metals for enhanced uptake. Yet no studies report the displacement of HMs in soil with sludge following solubilization with chelates. The objective of this work was to determine the uptake or leaching of HMs due to a chelate added to a soil from a sludge farm that had received sludge for 25 y. The soil was placed in long columns (105 cm long; ?? 39 cm) in a greenhouse. Columns either had a plant (hybrid poplar; Populus deltoides Marsh. × P. nigra L.) or no plant. After the poplar seedlings had grown for 144 d, the tetrasodium salt of the chelating agent EDTA was irrigated onto the surface of the soil at a rate of 1 g per kg of soil. Drainage water, soil, and plants were analyzed for three toxic HMs (Cd, Ni, Pb) and four essential HMs (Cu, Fe, Mn, Zn). At harvest, extractable and total concentrations of each HM in the soil with EDTA were similar to those in soil without EDTA. The chelate did not affect the concentrations of HMs in the roots or leaves. With or without plants, EDTA mobilized all seven HMs and increased their concentrations in drainage water. Lower concentrations of Cd, Cu, Fe, Ni, and Zn in leachate from columns with EDTA and plants compared to columns with EDTA and no plants showed that poplars can reduce groundwater contamination by intercepting these HMs in the soil. But the poplar plants did not reduce Pb and Mn in the leachate from columns with EDTA. Concentrations of Cd and Pb in the leachate mobilized by EDTA remained above drinking‐water standards with or without plants. The results showed that a chelate (EDTA) should not be added to a soil at a sludge farm to enhance phytoremediation. The chelate mobilized HMs that leached to drainage water and contaminated it.     

Dissipation of cyanogenic glucosides and cyanide in soil amended with white clover (Trifolium repens L.)

The use of white clover (Trifolium repens L.) as green manure is common practice due to its high nitrogen content. White clover produces the two cyanogenic glucosides linamarin and lotaustralin, which release toxic hydrogen cyanide upon hydrolysis. The hydrolysis of cyanogenic glucosides and release of cyanide were studied in batch experiments with ground white clover added to soil at loadings of 75 g leaves per kg soil. Linamarin and lotaustralin were quickly hydrolysed with first-order rate constants of 0.026-0.0062 h⁻¹ (corresponding to half lives of 11-27 h) in sandy and loamy soils at natural moisture contents and 11 °C. Experiments with addition of pure cyanogenic glucosides and with sterilized soil material as well as addition of white clover to inert quartz showed that hydrolysis by plant glucosidases is partly inhibited in the soil matrix, but also that soil glucosidases present in soil contribute to degradation of the cyanogenic glucosides, and more so for linamarin than for lotaustralin. Cyanide was produced during the hydrolysis of the cyanogenic glucosides as seen by formation of HCN(g) and WAD-CN (Weak Acid Dissociable Cyanide) amounting to max. 5 and 50% of total-CN in the systems with white clover added to natural soils. However, the increase in WAD-CN was transient, due to subsequent dissipation of the compound caused by abiotic and microbial CN degradation. Due to WAD-CN dissipation in the top soils studied, long term effects of cyanide on sensitive microorganisms and plants are not expected. However, knowledge on the stability of WAD-CN in subsoil is lacking and warrants further investigations.     

小浪底低山丘陵区植物N素吸收特征及其与土壤因子的关系

 为探寻温带地区山地植物N素保存策略,找出影响植物N素回收率的环境因子,以便了解植物保持所吸收养分的机制,以小浪底库区山地为例,研究该区域3种生活型21种典型植物成熟绿叶中的N素含量、枯叶中N素含量以及N素回收效率（NRE）。结果表明:植物成熟绿叶中的N素含量和枯叶中N素含量有显著的正相关关系;所测定的21种植物NRE在17.4%～50.1%之间,平均值为28.8%,多数种的回收效率低于40%。测定的21种植物都属于N素回收不完全植物。不同生活型的植物其回收效率有显著的差异,一般表现为草本>灌木>乔木。植物叶片N素含量与土壤有机质、土壤N素含量和土壤含水量呈显著正相关;而NRE与土壤有机质、土壤N素含量和土壤含水量呈显著负相关关系。说明在研究区不利的土壤条件,可以导致植物NRE的提高,植物在不利的环境条件下,可以通过提高NRE等途径来应对环境的胁迫。     

重庆笋溪河流域河岸带水体-土壤-植物的氮磷特征及影响因素

为明晰重庆笋溪河流域河岸带水体、土壤和植物的氮磷特征及其影响因素,采用描述性统计、聚类分析、相关分析和冗余分析的方法,探讨三峡库尾小流域河岸带水体、土壤和植物的氮、磷含量特征、空间分布和各圈层氮磷的相关性及水体氮磷的影响因素.结果表明:(1)河岸带受河流区段影响,从上游到下游,水体氮磷与土壤全氮的含量先减小后增大,下游...