Incinerated Sewage Sludge Products as Amendments for Agricultural Soils: Leaching and Plant Uptake of Trace Elements

Preliminary leaching column and greenhouse plant uptake studies were conducted in two soils with contrasting characteristics amended with varying rates (0 to 148.3 Mg ha^?1) of incinerated sewage sludge (ISS) and weathered sewage sludge (WISS) to estimate the leaching losses of trace elements from the soils amended with incinerated sewage sludge by products and to evaluate the uptake and accumulation of these elements in various parts of Sorghum vulgaris var. sudanense Hitche. (“Sorgrass''), a Sorghum-Sudan grass hybrid. Results of this study indicated that leaching of Cr, Cd, Zn, Cu, Ni, Fe and Mn from soils amended with ISS and WISS increased with increasing rates of amendment. Results of the leaching column study further revealed greater leaching losses from coarse-textured soil compared to medium-textured soil and also from ISS amended soils than with WISS amended soils. Results further suggested that the type of element and the interaction between the element and soil properties affected the leachability of various trace elements. The uptake study indicated uptake and accumulation of trace elements by plant parts increased with increasing rates of amendments. Greater plant uptake and accumulation of trace elements were observed in plant parts grown in soils amended with ISS compared to that of WISS. Results also indicated a greater accumulation of trace elements in below ground part of the plants (roots) compared to that was observed in above ground parts (shoots). Limited data obtained from this one season preliminary studies demonstrated that incinerated sewage sludge products from wastewater treatment plants could be used as soil amendments at low application (no more than 24.7 Mg ha^?1) for optimum plant growth, and dry matter yield without resulting in substantial accumulation of metals in plant parts at concentrations above the recommended critical limits and without causing significant leaching losses of various trace elements. It is imperative that long-term field studies are necessary to evaluate the long-term impact of using these new products in leaching and accumulation of various trace elements in plants and soils.     

Corn uptake of bromide under greenhouse and field conditions

Abstract

Bromide (Br) has been used frequently to trace the movement of fertilizer derived nitrate (NO₃) through the soil profile. Although not required for plant growth, Br is readily absorbed by plants. Consequently, the pulse of an anion tracer moving through the soil can be attenuated by actively growing plants. Greenhouse and field experiments were conducted to determine the amount of Br absorbed by corn, and to better understand potential competitive interactions between nitrogen (N) and Br in plant uptake. Under greenhouse conditions, over 85 percent of applied Brwas recovered by corn tops. Results from both greenhouse and field experiments demonstrated that the addition of Br or Cl neither reduced yield nor inhibited N uptake. Therefore, either Br or Cl could be used in N trials without concern for competitive inhibition of N uptake. However, both experiments demonstrated that N treatments affected Br concentration in the tissue, but this difference may have been due to increased yield of N treated plants causing Br dilution. Nitrogen treatments significantly affected plant Br uptake, but only in the greenhouse study. In the field experiment, corn recovery of 100 kg Br/ha applied in the spring of 1988 was as high as 38 percent in 1988, and 11 percent in 1989. This high rate of recovery demonstrates that the pulse of Br can be significantly reduced in the presence of developing plants, and should be taken into account when it is used as a tracer in leaching studies.     

Antimony Accumulation in Wheat Seedlings Grown in Soil and Water

The purposes of the research were (1) to estimate the ability of wheat Triticum aestivum L. to uptake antimony (Sb) from contaminated soil and water, (2) to study effects of Sb bioaccumulation on the plant development and distribution of macro- and trace elements in the plants, and (3) to compare uptake of Sb and some other elements by wheat seedlings grown in solid (soil) and liquid (water) media. Both soil-grown and water-grown plants were capable of accumulating large amounts of Sb. In roots, concentration of Sb was always greater than in leaves, suggesting that roots can prevent transfer of the trace element to upper plant parts. Uptake of Sb by the plants grown in water was significantly greater compared to Sb uptake by the plants grown in soil. Antimony bioaccumulation resulted in variations in concentrations of some nutrients in different plant parts and decrease of the seedling biomass.     

Uptake of multielements by corn from fly ash-compost amended soil

Fly ash was collected from a coal-fired power plant in and near the U.S. Department of Energy Savannah River Site to study the feasibility of the application of fly ash compost mixture to soils for the availability and uptake of various elements by corn (Zea mays L.). The crop was grown in potted Ogeechee sandy loam soil using eight treatments: soil alone, soil amended with 15% compost, and soil amended with 2, 5, 10, 15, 20 and 25% of fly ash-amended compost. It was observed that 20–25% fly ash and compost soil ratio treatments generally increased plant growth and the yield. The plant uptake of K, Mn, and Cu increased with increasing percentages (2–25%) of fly ash+compost: soil ratios. The total content of K in plants was positively correlated with the dry matter yield of corn. This study indicates that the application of fly ash blended with compost to soil is beneficial to corn production without causing any deleterious effects on plant growth and plant composition.     

GROWTH AND NUTRITION OF M.26 EMLA APPLE ROOTSTOCK AS INFLUENCED BY TITANIUM FERTILIZATION

The objective of this study was to examine the effect of different mode of titanium (Ti) fertilization on growth and nutrition by M.26 EMLA apple rootstock (Malus spp.) grown in three soils with diverse physical and chemical properties. Soils were taken from Warszawa, Grojec and Brzezna regions (fruit growing regions) of Poland. The experiment was carried out during 120 days in a greenhouse. The following treatments were applied: soil Ti fertilization at a rate of 2 and 4 mg Ti per plant and four- and eight-times Ti sprays at a rate of 0.5 mg Ti per plant in each spray. Titanium was applied as TiCl₄. Plants unfertilized with Ti served as control. Titanium sprays increased levels of this element in leaf and stem tissues. Soil Ti applications had no effect on Ti concentrations in plant tissues except plants grown in Warszawa soil where root tissue had higher Ti status compared to those of control plants. Foliar Ti applications enhanced plant dry matter and levels of phosphorus (P), iron (Fe), manganese (Mn), and zinc (Zn) in leaf tissues only in Brzezna soil. Leaves of plants sprayed with Ti grown in Brzezna soil were greener and had higher concentrations of Fe²⁺ and chlorophyll than those of control plants. These results suggest that the primary reason for higher biomass in plants sprayed with Ti was higher leaf Fe²⁺ level, which enhanced chlorophyll synthesis and uptake of P, Fe, Mn, and Zn.     

Leaf elemental concentrations and grain yield of sorghum grown on an acid soil

Abstract

Determination of the nutrient requirements of sorghum [Sorghum bicolor (L.) Moench] grown on acid soils is, a critical step in the development of plants which are adapted to these problem soils. Sorghum genotype, environment, and soil type interact with the uptake of elements and affect plant growth and production. This study compared the yields of a sorghum grain hybrid grown on a sandy loam soil at four acid pH levels. Nutrient concentrations in sorghum leaves on these soil regimes were also investigated. Grain yields declined 96% as soil pH decreased from 5.5 to 4.4. Leaf element analysis revealed that as pH decreased from 5.5 to 4.4, there was an increase in plant Al, Fe, Mn, K, P and a decrease in Cu, Zn, Mg, Ca. Interactions among several of these elements were readily apparent. Additional data involving different sorghum genotypes and different soil types are needed to establish a consistent pattern of element uptake on acid soils in relation to yield and plant production.     

特大暴雨下油松林根系对土壤元素迁移的影响

根际是元素由土壤进入植物体的主要界面,降水对根际土壤元素的迁移有显著影响。本文用原状土柱淋滤实验装置及大型挖掘剖面壁法,定量分析了特大暴雨下不同深度土层油松林根系影响土壤元素的稳定输出通量的剖面特征,旨在探索黄土区林木根系对土壤养分生物有效性的提高途径。研究结果表明,特大降雨条件下,油松林地的元素随土层深度增加呈明显的递减规律,在农地土壤剖面中变异不明显。油松林地元素稳定输出通量的平均值显著大于无根系土壤。油松林030.cm土壤剖面中的元素输出通量占总剖面元素输出通量的96.32%;油松林根系对常量元素K、Na、Mg、Ca、有益元素Si、微量营养元素Mn有明显稳定强化作用的土层深度范围为030cm,对有益元素Al和微量元素Cu、Fe有明显稳定强化作用的土层深度范围为045.cm。     

Response of Vigna Unguiculata Grown Under Different Soil Moisture Regimes to the Dual Inoculation with Nitrogen-Fixing Bacteria and Arbuscular Mycorrhizal Fungi

The interaction between legumes, rhizobial and arbuscular mycorrhizal (AM) partners benefits plant nutrition and improves plant tolerance to water stress. The present research evaluated the effectiveness of symbioses between cowpea plants (Vigna unguiculata (L.) Walp.), AM fungi (Glomus intraradices) and two strains of Bradyrhizobium japonicum on the mycorrhization, acid phosphatase activity (APase), enzymes related to nitrogen fixation and assimilation, and biomass accumulation at three soil moisture levels. The results revealed that the soil moisture optimal for the formation of active symbiotrophic associations in cowpea cultivation was about 60% water-holding capacity (WHC), where both Bradyrhizobium strains and AM fungi function well with respect to mycorrhization, nitrogen and phosphorus uptake, nitrogen fixation and plant biomass production. Under conditions of reduced water supply, the symbiotic association between Br. japonicum-273 and Gl. intraradices was better for cowpea cultivation, while in elevated soil moisture association between Br. japonicum-269 and Gl. intraradices was more appropriate.     

Comparison of Four Different Extraction Methods to Assess Plant Availability of Some Metals in Organic Forest Soil

Abstract

The objective was to find an uncomplicated test giving the best correlation between calcium (Ca), magnesium (Mg), manganese (Mn), copper (Cu), zinc (Zn), and lead (Pb) extracted from humic forest soil and the total concentration of the element in some understorey forest plants using well‐known extractants. The elements were selected because Ca, Mg, Mn, Cu, and Zn are essential nutrients to plants and Zn and Pb are potentially harmful heavy metals received over the years in the southern parts of Norway by long‐range atmospheric transport. Extraction of organic podzolic surface soil (Oe and Oa horizon) from 17 different pine forests in central and southern Norway was carried out with four different reagents to evaluate uptake of Ca, Mg, Mn, Cu, Zn, and Pb in the understorey plants Deschampsia flexuosa, Vaccinium myrtillus (leaves and stems), and Vaccinium vitis‐idaea (leaves and stems). The NH₄OAc, NH₄NO₃, HCl, and EDTA solutions used to extract the soil in addition to concentrated HNO₃, demonstrated variability in capacity to extract the different elements from the soil. The extractants yielded significant relations between concentrations of Ca, Mn, and Pb in the Oe or Oa horizon and some of the plants or plant compartments, even though distinct correlation was more dependent on species and plant part than the actual extractant used. In the case of Zn, Cu, and Mg only a few sporadic correlations were observed between the different plant/plant compartments and the element concentrations in the soil extracts. Altogether none of the extractants was shown to be superior to the others in providing the best correlation with the elements concentrations in selected plant/plant compartments. In the case of Ca, Mn, and Pb all the extractants including concentrated HNO₃ provided significant correlations with at least some of the selected plant/plant compartments.     

Genotype x environment interaction in the uptake of Cs and Sr from soils by plants

The soil‐plant transfer factors for Cs and Sr were analyzed in relationship to soil properties, crops, and varieties of crops. Two crops and two varieties of each crop: lettuce (Lactuca sativa L.), cv. Salad Bowl Green and cv. Lobjoits Green Cos, and radish (Raphanus sativus L.), cv. French Breakfast 3 and cv. Scarlet Globe, were grown on five different soils amended with Cs and Sr to give concentrations of 1 mg kg^–1 and 50 mg kg^–1 of each element. Soil‐plant transfer coefficients ranged between 0.12–19.10 (Cs) and 1.48–146.10 (Sr) for lettuce and 0.09–13.24 (Cs) and 2.99–93.00 (Sr) for radish. Uptake of Cs and Sr by plants depended on both plant and soil properties. There were significant (P ≤ 0.05) differences between soil‐plant transfer factors for each plant type at the two soil concentrations. At each soil concentration about 60 % of the variance in the uptake of the Cs and Sr was due to soil properties. For a given concentration of Cs or Sr in soil, the most important factor effecting soil‐plant transfer of these elements was the soil properties rather than the crops or varieties of crops. Therefore, for the varieties considered here, soil‐plant transfer of Cs and Sr would be best regulated through the management of soil properties. At each concentration of Cs and Sr, the main soil properties effecting the uptake of Cs and Sr by lettuce and radish were the concentrations of K and Ca, pH and CEC. Together with the concentrations of contaminants in soils, they explained about 80 % of total data variance, and were the best predictors for soil‐plant transfer. The different varieties of lettuce and radish gave different responses in soil‐plant transfer of Cs and Sr in different soil conditions, i.e. genotype x environment interaction caused about 30 % of the variability in the uptake of Cs and Sr by plants. This means that a plant variety with a low soil‐plant transfer of Cs and Sr in one soil could have an increased soil‐plant transfer factor in other soils. The broad implications of this work are that in contaminated agricultural lands still used for plant growing, contaminant‐excluding crop varieties may not be a reliable method for decreasing contaminant transfer to foodstuffs. Modification of soil properties would be a more reliable technique. This is particularly relevant to agricultural soils in the former USSR still affected by fallout from the Chernobyl disaster.     

Bedeutung von Kaliumaufnahmerate,Wurzelwachstum und Wurzelhaaren für das Kaliumaneignungsvermögen verschiedener Pflanzenarten

Effect of K uptake rate, root growth and root hairs on potassium uptake efficiency of several plant species Pot experiments with maize, rape, tomato, rye-grass and onion plants were carried out to evaluate the influence of – rate of K uptake per cm of root, – cm root per mg shoot dry weight and – mean root age (as a measure of the time roots absorb potassium) on potassium uptake efficiency of these plants. Percent K in shoot dry matter was used to indicate K uptake efficiency. No close correlation was observed between one of these factors to K concentration in shoot dry matter. The product of K uptake rate and root-shoot ratio was closely related to the K concentration of shoots. However, regression lines for maize, rape and onion were different. One single regression line was found when K concentration in shoot was related to the product of K uptake rate, root-shoot ratio and mean root age. It is therefore concluded that K uptake of plants depends on all three of these factors. In different species the proportion of these factors were markedly different. The plant factors in turn were affected by the K nutritional status of the plants. K uptake rate increased whereas root-shoot ratio and mean root age decreased with increasing K supply of the soil. K uptake rate per cm root was strongly affected by root hairs. The radial distance of the K (Rb) depletion zone of the soil adjacent to the root surface also increased with the length of the root hairs. It is therefore concluded that root hairs substantially affect the spatial access of potassium in soil by the plant.     

Silicon uptake by wheat: Effects of Si pools and pH

Silicon (Si), although not considered essential, has beneficial effects on plant growth which are mostly associated with the ability to accumulate amorphous (phytogenic) Si, e.g., as phytoliths. Phytogenic Si is the most active Si pool in the soil–plant system because of its great surface‐to‐volume ratio, amorphous structure, and high water solubility. Despite the high abundance of Si in terrestrial biogeosystems and its importance, e.g., for the global C cycle, little is known about Si fluxes between soil and plants and Si pools used by plants. This study aims at elucidating the contribution of various soil Si pools to Si uptake by wheat. As pH affects dissolution of Si pools and Si uptake by plants, the effect of pH (4.5 and 7) was evaluated. Wheat was grown on Si‐free pellets mixed with one of the following Si pools: quartz sand (crystalline), anorthite powder (crystalline), or silica gel (amorphous). Silicon content was measured in aboveground biomass, roots, and soil solution 4 times in intervals of 7 d. At pH 4.5, plants grew best on anorthite, but pH did not significantly affect Si‐uptake rates. Total Si contents in plant biomass were significantly higher in the silica‐gel treatment compared to all other treatments, with up to 26 mg g^–1 in aboveground biomass and up to 17 mg g^–1 in roots. Thus, Si uptake depends on the conversion of Si into plant‐available silicic acid. This conversion occurs too slowly for crystalline Si phases, therefore Si uptake from treatments with quartz sand and anorthite did not differ from the control. For plants grown on silica gel, real Si‐uptake rates were higher than the theoretical value calculated based on water transpiration. This implies that Si uptake by wheat is driven not only by passive water flux but also by active transporters, depending on Si concentration in the aqueous phase, thus on type of Si pool. These results show that Si uptake by plants as well as plant growth are significantly affected by the type of Si pool and factors controlling its solubility.     

Effects of soil amendments on antimony uptake by wheat

Purpose

Environmental chemistry of antimony (Sb) is still largely unknown. Many questions remain about its availability to plants and effects of fertilizers on mobility of Sb in the rhizosphere soil. In this work, we focused on the following problems: (1) uptake of Sb by wheat seedlings grown in soil enriched with this metalloid and (2) impact of soil amendments on the plant growth, Sb uptake from soil, and its transfer from roots to upper plant parts.

Materials and methods

To obtain further information on the possible transfer of Sb into plants, greenhouse pot experiments were carried out. Soil was spiked with 15 mg kg^?1 of Sb and amended with either chicken manure or natural growth stimulator Energen. Wheat Triticum aestivum L. seedlings were grown in the soil during 17 days. Plants together with rhizosphere soil were collected several times in the course of the experiment. The ICP-OES and ICP-MS techniques were applied to determine the concentrations of macro- and trace elements in the plant and soil material.

Results and discussion

Growth of wheat seedlings in Sb-spiked soil resulted in Sb accumulation in roots and leaves of the plants. Energen and especially chicken manure were capable of stimulating transfer of Sb to more mobile and, as a consequence, more available to the plants form, thus enhancing both uptake of Sb from soil and its transfer from roots to upper plant parts. The accumulation of Sb by plants led to a decrease of Sb concentration in the rhizosphere soil with time, and the most significant decrease was observed after amendment of soil with fertilizers.

Conclusions

Fertilizers may be used to increase phytoextraction of Sb and its removal from contaminated soils. However, such an amendment of soil should be done with caution in order to exclude or at least reduce the negative effects on plants.     

Effects of Biofertilizers on Maize and Sunflower Seedlings under Cadmium Stress

Application of various alternative nutrient supplies can partly be substituted by chemical fertilizers, resulting in economical use with less environmental strains. Biofertilizers containing living microorganisms promote nutrition uptake, but still there are questions regarding their application under stress conditions. One of the main abiotic factors that can induce stress is contamination of soils with toxic elements. In the course of intensive plant-growth conditions, considerable quantities of basic cations are removed from the soil, resulting in acidification and thereby enhancing the uptake of heavy metals by plants. Cadmium (Cd) toxicity is a major problem affecting crop productivity worldwide. The presence of Cd in the rhizosphere can cause stress responses and alteration in many physiological processes, including nitrogen metabolism, photosynthesis, carbohydrate metabolism, sulfate assimilation, and plant–water interactions. Once in the plant, Cd can enter the food chain, causing public health problems. The aim of our work was to investigate the effects of biofertilizers on plant production and nutrient uptake in some Cd-contaminated soils. Our results revealed that Cd accumulated primarily in the roots and transport to the shoots was rather low; however, there were differences between the two plants species. Plant uptake by sunflower was greater than by maize, and sunflower appeared to be more stress tolerant of Cd than maize. With the use of the bacterium-containing biofertilizer, the toxic effect of Cd was moderated.     

Environmental Impact on an Arctic Soil–Plant System Resulting from Metals Released from Coal Mine Waste in Svalbard (78° N)

Impact of acid mine drainage (AMD) from a coal mine waste rock pile deposited within a permafrost-affected Arctic ecosystem was investigated near Longyearbyen (Svalbard, 78° N). Analyses included metal concentrations (Al, Fe, Mn, Zn, Ni, Cr, As and Pb) in runoff, soil and plants. It was observed that impacts of AMD, such as plant degradation, were similar to impacts reported from non-arctic ecosystems. It was found that bio-available metal concentrations in soil samples were not useful in assessing potential plant toxicity, as metals were not accumulated in the most impacted area due to low soil pH (pH?<?4). Native graminoid plants in the high impacted area showed accumulation of all the investigated elements. Al, Mn and As were found at phyto-toxic concentrations. Metal uptake in two native graminoid plants was studied in the laboratory. Positive correlations were noted between metal concentrations and plant uptake for all metals investigated, except Fe. High Fe concentrations found in plant samples in the impacted area are considered a result of Fe-oxide precipitation (plaque) on leaves during the spring flush when runoff covers the plants. We conclude that the weathering products Al, Mn and Fe induce the largest negative impact on vegetation in the area, and that a major fraction of the annual uptake of metals occurs during spring flushes. During these flushes, metals produced from weathering processes throughout the winter are released in high concentrations, coinciding with low pH values, low infiltration rates due to permafrost and the start of the plant growth season.     

不同高粱种质对污染土壤中重金属吸收的研究

利用重金属含量较高的污水污染土壤,以未污染土壤作对照,种植8个甜高粱品种、2个饲用高粱品种和1个粒用高粱品种,检测8种重金属在高粱植物体内不同器官的含量,以研究不同高粱种质对重金属的吸收特性。结果表明:甜高粱对汞(Hg)、镉(Cd)、锰(Mn)和锌(Zn)的吸收在两种土壤间差异显著,对钴(Co)、铬(Cr)、铅(Pb)和铜(Cu)的吸收差异不显著。Mn在甜高粱体内含量表现为未污染土壤高于污染土壤;而Zn含量在不同器官之间存在差异,未污染土壤叶中含量远高于穗,穗中含量远高于茎和根。不同重金属在甜高粱体内的储存部位不同,污染土壤上Hg、Cd、Co、Cr和Zn在根中积累量较高,Cu、Mn和Pb在穗中的积累量较高。甜高粱、饲用高粱和粒用高粱对重金属的吸收、运输及储存在品种之间差异较大,同一品种对不同重金属的吸收也存在差异。饲用高粱表现为叶部对Cr和Zn的储存量较高,而粒用高粱‘晋中0823’则显示了茎对多种重金属的储存能力。高粱根对土壤中重金属的富集系数较高,为0.02(Pb)~0.23(Cd),转移系数变幅为0.21(Co)~3.42(Pb)。对同一种重金属的吸收量品种间差异较大,甜高粱‘西蒙’根对Co、Cr、Cu、Mn、Pb和Zn具有高富集系数,粒用高粱‘晋中0823’茎对Hg、Cd、Mn、Pb和Zn富集系数较高。高粱对重金属的吸收能力与转移能力不同步,甜高粱‘绿能1号’具有对多种重金属的高转移能力,粒用高粱‘晋中0823’只对Zn有较高的转移能力。因此本文认为甜高粱对不同重金属的吸收和转移有选择性。对Zn吸收并转移到地上部后,首先储存在叶和穗中,当吸收量足够大时,茎和根也成为储存器官;对Mn的吸收与其他重金属的吸收存在竞争作用,Hg吸收后很少向地上部转移;而对Cu、Mn和Pb吸收后在穗部的储存量较大。饲用高粱与甜高粱相比对重金属的吸收未显示明显的不同,甜高粱‘西蒙’根对多种重金属具有强储存能力,而粒用高粱‘晋中0823’的茎秆显示了比甜高粱更强的储存能力,甜高粱‘绿能1号’对多种重金属的转移能力较强。所以,选择富集和转移能力均强的高粱品种能更有效地吸收土壤中的重金属,达到修复污染土壤的目的。     

Effect of zinc on some important macro‐ and microelements in blackgram leaves

Abstract

Blackgram (Vigna mungo L.) plants were grown in glasshouse earthen pot experiment. Zinc (Zn) was applied to the soil at different concentrtions. Plant leaf samples were analysed at the age of 30, 45, and 65 days after sowing. The accumulation of Zn in the plant increased with the applied Zn concentration to the soil. Also a variation in the uptake of Zn by the plant with age has been observed. The excess accumulation of Zn in the plant induced a reduction in the content of some macro‐ [calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na)] and micro‐elements [iron (Fe), manganese (Mn), and copper (Cu)] in the plant leaves. Furthermore, the Ca: Zn ratio decreased with increasing Zn concentration which clearly indicates a toxic Zn effect on blackgram plants.     

Soil-plant nutrition studies on tropical rice VI. The effect of different levels of nitrogenous fertilizer application on plant growth,grain yield,and nitrogen utilization by rice plants

The effect of different levels of nitrogenous fertilizer application on plant growth, grain yield, and both the amount of soil nitrogen and applied fertilizer nitrogen utilized by plants was investigated in the Bangkhen paddy field. The results furnished clear evidence that the recoveries of added fertilizer nitrogen by plants were increased along with an advance in plant growth, and that the plant uptake of soil nitrogen was independent of the nitrogen level applied. A linear relation was found between total nitrogen absorbed by plants and the levels of nitrogen applied indicating that the extrapolated yield of the nitrogen value could be used for the evaluation of the soil nitrogen supply. The present study demonstrated also the importance of examining the proportion of two kinds of nitrogen in plants, one derived from fertilizer and the other from soil nitrogen, in the evaluation of the fertilizer effect, and made it clear that the evaluation of fertilizer effect based only on the quantity of fertilizers absorbed by plants represents only a part of the whole picture.     

Soil versus plant as indicators of agroecosystem pollution by potentially toxic elements

The major route of potentially toxic elements (PTEs) to humans is the intake through food. They enter the food chain principally by plants uptake from the soil and, to a less extent, through foliar deposition. The soil‐to‐plant transfer as part of the biogeochemical cycle of these elements is a complex and hardly predictable process. In this study, we investigated the capability of soils and plants to indicate PTEs inputs in an intermingled urban‐rural landscape of south Italy affected by legal and illegal waste disposal and dumping. For this aim, 172 agricultural soil and plant (edible part) samples were collected in pairs from 47 municipalities and analyzed for 12 PTEs (As, Be, Cd, Co, Cu, Cr, Ni, Pb, Se, Tl, V, Zn). Soil extractions with 1 M NH₄NO₃ and 0.05 M EDTA pH 7 were applied to assess PTEs bioavailability. Results were examined according to plant species and main soil chemical properties. For Pb and Cd, the soil‐to‐plant transfer factors (TF) and the corresponding soil benchmark concentrations were also investigated. Zinc, Cu, Cd, and Pb were the only PTEs of anthropic origin severely polluting from 10 to 16% of the soils, but only in a very few cases exceeded physiological or EU legal critical values in the edible part of the plants. An evaluation of human risk due to the ingestion of these elements was tried; no risk for consumers for Zn, Cu, and Pb, while for Cd three values slightly exceeded the tolerable daily intake. Therefore, we conclude that crops cultivated in the studied area could represent only a moderate risk for human health. No correlation was found between soil and plant data, which likely highlights different pollution inputs. A large variability characterized the Pb and Cd TF, making it difficult to establish a unique benchmark concentration for the studied agricultural soils.     

运用生物法对褐土和潮土不同土层供钾能力的研究

运用玉米苗对褐土、潮土不同层次土壤进行了钾素生物耗竭试验 ,发现 :当土壤有效钾素趋向匮乏时 ,首先受到影响的是玉米苗的干生物产量 ,其次是植株总吸钾量 ,再其次才是植株含钾量 ;矿物钾对植株吸钾是有贡献的 ,但其贡献率因土壤不同而有很大的差异 ,褐土矿物钾的贡献率比潮土的要大 ;交换性钾、非交换性钾的生物有效性因土类的不同而存在明显差异 ,总的说来 ,潮土较褐土能提供较多的钾素 ;土壤供钾性能随深度增大而减弱