The main objectives of this thesis are to study if a topographic wetness index (TWI) could be used as a tool for predicting the spatial distribution of vascular plant species richness in the boreal forest as well as to study congruence in species richness between vascular plants, liverworts, mosses and lichens. A wetness index ln(a/tanβ) based on topography was used to assign a specific TWI-value to every 20 x 20m grid in two 25 km2 boreal forest landscapes (differing in average soil pH) in northern Sweden. Soil pH is known to be influenced by groundwater and to affect plant species richness in other biomes. Therefore, the relationships between plant species richness, TWI and soil pH were also studied. The results showed that the majority of the investigated boreal forest landscapes were relatively dry and species-poor, whereas interspersed patches linked to areas with relatively high TWI had species-rich vegetation including the species of the drier parts of the landscape. There was a positive relationship between species richness of vascular plants and the TWI in both landscapes, but varied with average soil pH. TWI explained 30 % and 52 % of the variation in plant species richness in the landscape with lower and higher pH, respectively. The proportion of regionally uncommon plants also increased with TWI. Testing different calculation methods of the TWI resulted in a large variation in correlation strengths between the various TWI-values and different measured variables (species richness of vascular plants, soil pH, groundwater flow and soil moisture). The relationship between plant species richness and TWI could be further improved with some of the calculation methods. When studying correlations in species richness using data sets from boreal forest in northern Sweden, strong positive correlations among vascular plants, mosses and liverworts were found, but no significant correlation between macrolichens and any of the other groups. This result could be explained by that the species number of each of the three related groups increases with ambient moisture, whereas the species number of macrolichens is weakly associated with moisture. In conclusion, the TWI could become a useful tool in conservation management for identifying areas of special interest prior to field inventories. Since vascular plants can be used as an indicator taxon for species richness of mosses and liverworts, high TWI-values indicate areas of species hotspots of these taxa. / Syftet med avhandlingen är att dels studera om ett topografiskt fuktighetsindex skulle kunna vara användbart för att förutsäga fördelningen av kärlväxters artrikedom i boreal skog, dels att studera om den rumsliga fördelningen av artrikedom hos kärlväxter, blad- och levermossor samt lavar sammanfaller. Ett fuktighetsindex, ln(a/tanβ), som bara är baserat på topografi användes för att beräkna ett indexvärde för varje 20 x 20 m grid i två 25 km2 stora boreala skogslandskap (med i medeltal olika mark-pH) i norra Sverige. Det är känt att mark-pH påverkas av grundvatten och att pH i sin tur påverkar artrikedom hos kärlväxter i andra biom. Därför studerades även sambanden mellan kärlväxters artrikedom, mark pH och TWI. Resultaten visade att större delen av det studerade boreala landskapet var relativt torrt och artfattigt, medan mindre utspridda områden med höga TWI-värden var artrika på kärlväxter och här växte även arter som återfanns i de torra delarna av skogen. Sambandet mellan artrikedom hos kärlväxter och TWI var positivt i båda landskapen, men påverkades av de olika nivåerna på mark-pH. TWI förklarade 30 % av variationen i artrikedom i området med lägre mark-pH respektive 50 % i området med högre mark-pH. Andelen kärlväxter som klassificeras som icke vanliga i respektive region ökade också med TWI. Med andra beräkningsmetoder för TWI visade det sig att styrkan på korrelationerna mellan TWI och olika uppmätta variabler (artrikedom hos kärlväxter, mark-pH, grundvattennivå och markfuktighet) varierade mycket. Sambandet mellan artrikedom hos kärlväxter och TWI kunde förbättras ytterligare med vissa beräkningsmetoder. Då korrelationer i artrikedom studerades användes ett dataset från boreal skog i norra Sverige. Resultaten visade på starka, positiva korrelationer mellan kärlväxter, blad- och levermossor, men inga korrelationer mellan någon av dessa grupper och lavar. Detta kunde förklaras med att artrikedom hos de tre korrelerande organismgrupperna ökar med ökad fuktighet, medan artrikedom hos lavar inte är kopplat till fukt. Huvudslutsatsen i avhandlingen är att TWI, som endast är baserad på topograpfiskt data, skulle kunna bli ett värdefullt redskap i naturvårdsplanering för att identifiera särskilt intressanta skogsområden innan man gör fältinventeringar. Eftersom studien visar att kärlväxter kan användas som en indikator grupp för artrikedom hos blad- och levermossor indikerar höga TWI-värden områden med hög artrikedom även vad gäller dessa taxa.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2009. / Härtill 4 uppsatser.

Darbo tikslas: nustatyti ir palyginti tręšimo mineralinėmis trąšomis, pjuvenų kompostu ir miško kuro pelenais įtaką buvusiame Dumsių kariniame poligone kai kurioms smėlžemių fizikinėms ir cheminės savybėms bei įvertinti ten augančių pušies želdinių būklės ir augimo pagerinimo galimybes. Darbo objektas: smėlžemiuose augantys pušies želdiniai buvusiame Dumsių kariniame poligone; 2001 m. įrengti tręšimo mineralinėmis trąšomis bandymai ir 2005 m. įrengti bandymai, kuriuose kaip trąšos naudoti miško kuro pelenai ir pjuvenų kompostas. Darbo metodai: vizualiai 1 m² dydžio aikštelėse nustatytas dirvožemio žolinės dangos padengimas (%) (kiekviename variante sistemiškai išdėstyta po 5 aikšteles); išmatuotas (n=50) pušų prieaugis į aukštį ir vizualiai nustatytas spyglių pageltimas (dechromacija, %); nustatytas viršutinio mineralinio dirvožemio sluoksnio (0-5 cm; 5-10 cm ir 10-20 cm gyliai, jungtiniai ėminiai iš 20-ies vietų) pHCaCl2 rodiklis ir C, N ir S koncentracijos. Darbo rezultatai: išanalizuoti 2001-2005 metų duomenys; ištirtas tręšimo mineralinėmis trąšomis, pjuvenų kompostu ir miško kuro pelenais poveikis smėlžemių viršutinių horizontų pH rodikliui, C ir N koncentracijoms bei gyvąjai dirvožemio dangai, išanalizuotas ir palygintas pušies želdinių būklės ir augimo pagerėjimas, patręšus skirtingomis trąšomis. / The aim of the study: to determine and compare the influence of the application of the different doses of mineral fertilizers, sawdust compost and wood ash applied in complex with nitrogen on some physical and chemical properties of Arenosols in former military range area in Dumsiai; to evaluate the improvement possibilities of the condition and growth of Scots pine plantations in the area. The object of the study: Scots pine plantations growing on Arenosols in former military range area in Dumsiai; the fertilization trials where the mineral fertilizers were applied in 2001, and the fertilization trials where the sawdust compost and wood ash in complex with N fertilizers were applied in 2005 were further investigated. Methods: the ground vegetation cover (%) was visually assessed in 1 m² plots (5 plots were systematically laid in each treatment); height increment of Scots pine trees (n=50) was measured and discoloration of the needles (%) was visually assessed; mineral topsoil samples from 0-5 cm; 5-10 cm and 10-20 cm depths were collected (each combined sample was taken from 20 places), and chemically analysed for pHCaCl2, C and N concentrations. The results: the data of earlier investigations from the years 2001-2005 were analysed; the influence of the mineral fertilizers, sawdust compost and wood ash treatments on mineral topsoil pH, also the changes of N and C concentrations was analysed; the effects of the ground vegetation cover was assessed; the condition and growth... [to full text]

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 4 uppsatser.

O destino de metais pesados em solos é principalmente controlado por reações de sorção e de precipitação em superfícies minerais. Resultados de pesquisa têm evidenciado certa contradição quanto à mobilidade dos metais pesados em solos tratados com lodo de esgoto. Parte dos resultados permite afirmar que a mobilidade dos metais nesses solos é baixa ou nula, enquanto que outra parcela questiona a capacidade do solo em reter esses elementos, sendo esta capacidade função de fatores como tempo, nível de contaminação, condições climáticas, alterações químicas e degradação da matéria orgânica. O objetivo do trabalho foi avaliar a dessorção de Cd, Cu, Ni e Zn em função do pH, a capacidade adsortiva e a fitodisponibilidade desses metais em um Latossolo tratado por cinco anos consecutivos com doses de lodos provenientes das estações de tratamento de Barueri (LB) e de Franca (LF). Amostras de solo foram coletadas da camada 0-0,2m, dos seguintes tratamentos: testemunha; dose de lodo estabelecida para adubação nitrogenada da cultura do milho (1N); duas vezes (2N), quatro vezes (4N) e oito vezes a dose de lodo recomendada (8N). O efeito do pH na dessorção dos metais foi avaliado por meio da determinação da concentração dos mesmos em extratos obtidos em agitações seqüenciais, a primeira de 24 horas e as seguintes de 2 horas cada até a dessorção máxima, usando solução de Ca(NO3)2 0,01 mol L-1 (relação solo:solução de 1:10) e pH ajustado com HNO3 ou NaOH 1 mol L-1. A faixa de variação de pH investigada foi de 3,5 a 7,5. A adsorção dos metais foi avaliada nas amostras de solo agitadas com solução de Ca(NO3)2 0,01 mol L-1 e concentrações crescentes de cada metal. Plantas de arroz foram cultivadas pelo método de Neubauer para avaliação da fitodisponibilidade dos metais. A dessorção dos metais foi crescente com o aumento das doses dos lodos e o LB exibiu maiores valores comparativamente ao LF. A redução do pH proporcionou o aumento dos teores de metais dessorvidos. A capacidade adsortiva do solo também aumentou com a dose de lodo. As amostras tratadas com LF adsorveram mais metais que as tratadas com LB, concordando com os resultados de dessorção. As quantidades de metais nas plantas de arroz apresentaram boa correlação com os teores dessorvidos e com os extraídos do solo com DTPA, indicando que a fitodisponibilidade aumenta com o uso de lodo. Conclui-se que o pH do solo é fator importante no controle da disponibilidade dos metais e sua redução implica em menor capacidade do solo tratado com lodo em reter os metais estudados, além de existir também diferenças importantes relacionadas com as doses aplicadas e origem e características dos lodos de esgoto. / The fate of metals in the soil environment is mostly controlled by sorption reactions on the surface of soil constituents. There have been many studies on the mobility of metals in sludge-amended soils and some contradictions arise from them. Several results indicated a low or even null degree of mobility while others questioned the capacity of soils components in retaining those elements, which is dependent on degree of contamination, climatic conditions, chemical alterations and decomposition of organic matter. This thesis reports the evaluation of the of Cd, Cu, Ni and Zn dessorption from soils as function of pH; the adsorptive capacity and the biovailability of those metals in soil samples collected in a field trial where sewage sludge was applied during 5 consecutive years. The waste was collected in two sewage treatment plants: Barueri (LB) and Franca (LF) in São Paulo state, Brazil. Soil was sampled (0-20 cm) in the trail plots of the following treatments: check; sewage rate corresponding to the amount of total nitrogen recommended for maize (1N) and rates of 2, 4 and 8 times the 1N rate, which were identified as 2N, 4N and 8N, respectively. The pH effect on metal desorption was evaluated by a sequential extractions procedure with Ca(NO3)2 0.01 mol L-1 solution: the first step lasted 24 h and the subsequential ones 2 h till no significant amount of metal could be extracted. The soil: extractant solution ratio was 1:10 and the pH ranged from 3,5 to 7,5 obtained after proper additions of HNO3 or NaOH 1 mol L-1 solutions aliquots. Metal adsorption was carried out in Ca(NO3)2 0.01 mol L-1 solution with increasing metal concentration. A Neubauer-type trial was carried out with rice plants to evaluate metal bioavailability. Metal desorption increased with sewage rates and higher amounts were obtained for LB as compared to LF. Metal desorption also increased as pH decreased. Soil samples where LB sewage was applied adsorbed higher metal amounts, which is in accordance with desorption results. Metal bioaccumulation in rice plants in the Neubauer experiment was well correlated with the desorbed amounts and with the DTPA extracted values thus indicating that bioavailability rises when sewage sludge is applied. Soil pH appears as the key factor in controlling Cd, Cu, Ni and Zn availability and the more it decreases the less they are retained by soil. It should also be mentioned the striking effects of and sludge characteristics and rates.

Two field experiments were conducted on sandy loam soils in OKhahlamba Local Municipality (OLM) (Bergville area), KwaZulu-Natal province in South Africa, during the rainy seasons of 2014/15 and 2015/16 to study the effect of calcium source (gypsum) fertilizer application on yield and quality of groundnut (Arachis hypogaea L.). The household economy of OLM is mostly dependent on agriculture and the majority of farmers in this area are small-scale farmers subsisting mainly on maize (constituting the staple diet) and groundnut production. Crop diversification, therefore, becomes an important aspect for farmers, and this is traditionally done using crops that are produced in almost similar agronomic circumstances to that of maize under dryland conditions. A large proportion of the OLM population depend on groundnut as a vital supplement to their daily food requirements, particularly as a cheap source of protein for resource-poor farmers. Therefore, any scientific approach to increase the yield of groundnut should be considered important in the livelihood of this community. Moreover, groundnut is an excellent rotational crop, since it responds well to fertilizer applied to previous crop and maize, as well as to crop, since it responds well to fertilizer applied to previous crop and maize, as well as to nitrogen left over by peanut. Thus, farmers save money because they use less fertilizer. The consideration for this study was based upon the above. The experiment was laid in a randomised complete block design with factorial arrangement, which was replicated three times in 48 plots. The factors studied were four levels of gypsum (CaSO4.2H2O) i.e. 0 kg/ha, 500 kg/ha, 750 kg/ha, and 1000 kg/ha and four levels of lime (MgCO3.CaCO3) i.e. 0 kg/ha, 250 kg/ha, 500 kg/ha, 750 kg/ha. Soil pH, cation exchange capacity (CEC), electrical conductivity (EC), pod yield, seed yield, 100 seeds weight, shelling percentage, dry shoot weight, seed moisture content percentage at harvest, and leaf calcium concentration data were collected prior to, and post harvesting. The application of 500 kg gypsum/ha alone acted as a liming factor for legumes, decreasing acid stress on nodulating bacteria, and improved soil chemical properties (increased soil pH), vegetative growth, yield, and quality of groundnut. The smallholder famers can afford this application rate, since gypsum acts both as a liming factor and as a calcium source to improve crop yield. The application of 1000 kg gypsum/ha improved seed yield, shelling percentage as well as kernel weight, which is yield, and quality of groundnut under dryland conditions. Since smallholder farmers practise dryland production, it is advisable to adopt the application of gypsum at the rate of 1000 kg/ha to improve yield and quality of groundnuts. It was also found to be more economical than using both gypsum and lime. The application of 500 kg gypsum per hectare in combination with 250 kg lime per hectare produced the highest shelling percentage. This combination of two calcium sources (gypsum and lime) is not recommended for small-scale farmers because it is not economical. The application of 500 kg gypsum per hectare in combination with 750 kg lime per hectare increased pod yield. However, this combination is also not recommended because it is not cost-effective. The application of 1000 kg gypsum per hectare in combination with 500 kg lime per hectare increased seed yield and produced sound mature kernel (SMK), whereas the application of 1000 kg gypsum alone per hectare also increased seed yield. This combination is also considered unacceptable due to the high increase in input costs. The application of 750 kg lime per hectare was more effective as an acid ameliorant and led to the improvement of the chemical composition of the soil (increased soil pH), resulting in a higher shoot weight of groundnut. This application also provided the catalyst for stimulating phosphorus production and enhancing the growth of an extensive root system for absorbing water and nutrients. The use of lime in acid soils is highly beneficial because it improves the chemical composition of the soil, ensures the availability of nutrients to plants, serves as an efficient calcium source, and ultimately leads to an improvement in yield. Results show that the application of gypsum at 1000 kg/ha and lime at 500 kg/ha respectively, significantly improved peanut yield and soil pH. The combination of gypsum and lime (500 kg/ha gypsum and 250 kg/ha lime) significantly improved shelling percentage (yield). Based on data on yield, yield components, and soil chemical properties, it is concluded that gypsum is the best calcium source fertilizer for groundnut production in OLM and lime should only be applied on acid soils to attain optimum groundnut yield in the region / Agriculture, Animal Health and Human Ecology / M. Sc. (Agriculture)

In Canada, about 60% of contaminated sites involve petroleum hydrocarbon (PHC) contamination and most of these sites have been abandoned due to contamination. Among current technologies used for soil remediation, supercritical fluid extraction (SFE) is a relatively recent and potentially viable method. The main aim of this research was to investigate the application of SFE for removal of PHCs from contaminated soils. In the first phase, the effects of SFE operational parameters including fluid pressure, fluid temperature, time duration and mode of extraction on the removal efficiency of PHCs from a spiked sandy soil (with diesel fuel with a ratio of 5 wt%) were investigated. SFE experiments were performed at different pressures (15, 33 and 50 MPa) and temperatures (30, 75 and 120 °C). The combination of 10 min static mode followed by 10 min dynamic mode, repeated for 3 cycles (60 min in total) led to the highest PHC removal percentage. According to response surface methodology (RSM), the optimum pressure and temperature were found to be 50 MPa and 69.3 °C, respectively. According to experimental results, the optimum combination of pressure and temperature determined to be 33 MPa and 75 °C; which resulted in the extraction percentages of 99.2%, 91.7% and 86.1% for PHC F2, F3 and F4 fractions, respectively. In the second phase, the influence of several parameters including soil water content, soil pH and addition of modifier on PHCs removals from a field-contaminated sandy soil using SFE were experimentally investigated. SFE experiments were performed at 33 MPa pressure and temperatures of 45 and 75 °C. Three water content levels of 8%, 14% and 20% at two levels of pH 6.5 and 7.5 were investigated. The extraction of total petroleum hydrocarbon fractions (TPHF), the sum of F2, F3, and F4 fractions, decreased due to the increase in the water content from 8% to 20% at both pH 6.5 and 7.5. The difference of extractions of all PHC fractions at pH values of 6.5 and 7.5 were not statistically significant (at p < 0.05 confidence level) at all three water content levels and pH did not have a significant influence on the PHC removal efficiency. Addition of acetone as a modifier (33.7% TPHF removal) was more effective than hexanes (24.3% TPHF removal) to decrease the concentrations of PHCs for the field contaminated soil. In the third phase, the influence of soil texture and grain size on the extraction of PHC fractions was investigated. SFE experiments were performed at 33 MPa pressure and 75 °C temperature. Three types of soils (soil A, B and C) were spiked with diesel fuel with a ratio of 5 wt%. Soil A, B and C had different particle sizes and were categorized as sand, silt loam and clay, respectively. Soil A (sand) which had the largest particle size resulted in the highest TPHF removal percentage while soil C (clay) with the smallest particle size led to the lowest TPHF removal percentage. A higher clay content in soil C resulted in a lower extraction of PHCs. In the fourth phase, the effects of pressure and temperature on the extraction of PHC fractions from a clay soil spiked with diesel fuel with a ratio of 5 wt% were investigated. SFE experiments were performed at three pressures (15, 33 and 50 MPa) and temperatures (30, 75 and 120 °C). According to the statistical analysis including factorial design and RSM, the optimized combination of pressure and temperature was selected at 42.8 MPa and 120 °C; which resulted in the removal percentages of 74.9% and 65.6% for PHC F2 and F3 fractions, respectively. The optimum combination of pressure and temperature based on the experimental results was selected at 33 MPa and 120 °C that led to 70.3%, 58.4% and 32.6% removal of PHC F2, F3 and F4 fractions, respectively.

La déficience des sols en éléments minéraux, particulièrement le phosphore (P) est une limitation majeure pour la croissance et le développement des légumineuses fixatrices d’azote. L’application des fertilisants phosphatés est une pratique traditionnelles pour satisfaire les besoins des plantes en P. Ainsi, pour tester l’efficacité d'utilisation du P pour la fixation symbiotique de l’azote (FSN) sous déficience en P, plusieurs lignées recombinantes (RILs) de haricot contrastantes dans leurs tolérance au déficit en P ont été utilisées. L’objectif principal de cette étude est d’évaluer l’aptitude de ces RILs pour l’amélioration de la fertilité phosphatée des sols déficients en P et sa relation avec la croissance et la nodulation de la légumineuse. Pour atteindre ces objectifs, des expériences ont été réalisées sous serre et en champs d'agriculteurs. Sous conditions contrôlées (serre) et non contrôlées (champs), les résultats ont montré une diminution du pH des sols associée à une augmentation du P assimilable. Une telle augmentation de la disponibilité du P a eu un effet positif sur la nodulation et la croissance de certaines des RILs testées. Aussi, l’amélioration de l’aptitude de ces RILs à fixer l’azote atmosphérique et l’élévation de la libération des protons H+ par les racines nodulées ont été quantifiés en milieu contrôlé. Ainsi la diminution du pH du sol a permis de réduire l’indisponibilité du P dans la solution du sol en le transformant en une forme directement biodisponible pour ces plantes. En outre, les résultats ont montré des différences significatives entre les différentes RILs en termes de la biomasse aérienne et nodulaire selon les sites d'observation. Nous concluons que, outre leur aptitude de fixation d’azote, l’utilisation efficace du phosphore pour sauver des engrais minéraux et de réduire les risques de pollution et pourrait améliorer la disponibilité des sols P. / The deficiency of soil minerals, particularly phosphorus (P) is a major limitation for growth and development of nitrogen-fixing by legumes. The application of phosphate fertilizers is a traditional practice to meet the needs of plant P. Thus, to test the effectiveness of use of P for symbiotic nitrogen fixation (NSF) under P deficiency, several recombinant inbred lines (RILs) of beans in their contrasting tolerance to P deficiency have been used. The main objective of this study is to assess the ability of these RILs to improve the fertility of soils deficient in phosphorus (P) and its relationship with growth and nodulation of the legume. To achieve these objectives, some experiments were conducted in greenhouses and fields. Under controlled conditions (greenhouse) and uncontrolled conditions (field), the results showed decreasing in soil pH associated with Proton release H+ and P acquisition. The increasing in available P had a positive effect on nodulation and growth of some RILs tested. Also, improving the ability of these RILs to fix atmospheric nitrogen and release H+ by nodulated roots were quantified in a controlled environment. Thus the decreasing in soil pH has reduced the un-availability of P in soil solution by transforming it into a bio-available form to the plants. In addition, the results showed significant differences between RILs in biomass and nodulation as observation in sites. We conclude that, in addition to their ability to fix nitrogen, effective use of phosphorus to save mineral fertilizer and reduce the pollution risks and could improve the availability of soil P.

O comportamento do Ni no solo, principalmente quando adicionado através de biossólidos, ainda é pouco conhecido. Este trabalho objetivou avaliar a influência dos teores totais do metal, de matéria orgânica e dos valores de pH na distribuição daquele elemento no solo e na sua biodisponibilidade. Foram conduzidos três experimentos de incubação em vasos mantidos em casa de vegetação, utilizando 3 kg de amostras da camada de 0 - 0,20 m de dois solos: ARGISSOLO VERMELHO AMARELO Distrófico (PVAd) e NITOSSOLO VERMELHO Distrófico Latossólico (NVdl). Dois experimentos foram montados em solos diferentes, em esquema fatorial 2x2x3, nos quais 2 doses de Ni (21 e 42 Kg ha –1 ) como NiCl2, foram incubadas durante 120 dias, sob dois teores de matéria orgânica e dois valores de pH, obtidos pela adição de turfa e de calcário, respectivamente. Num terceiro experimento fatorial (2x4), os mesmos dois solos foram incubados por 150 dias com a dose de 150 Mg ha -1 de quatro diferentes biossólidos. Posteriormente, cultivou-se alface em todos os vasos por 50 dias Após a incubação, amostras de solo foram analisadas quimicamente, inclusive efetuando-se extrações seqüenciais para determinar a distribuição do Ni adicionado através de NiCl2 e de biossólido. Foram consideradas as frações do metal solúvel + trocável, carbonatos, matéria orgânica, óxidos e residual. Realizou-se também a especiação do Ni baseada no equilíbrio de Donnan, no extrato de saturação das amostras, para discriminar a porção do Ni solúvel que se achava na forma de íon livre. O calcário foi o fator que mais afetou o comportamento do metal, reduzindo a concentração na fração trocável e aumentando-a nas frações matéria orgânica e óxidos. A turfa aumentou os teores do metal na fração trocável e os reduziu nas frações óxidos e matéria orgânica. O NiCl2 aumentou o teor de Ni nas três frações citadas. Os teores do metal nas frações de cada solo foram modelados por equações de regressão, em função dos teores de C-orgânico, Ni total e pH do solo. A distribuição do Ni no solo, quando adicionado através de biossólidos apresentou semelhanças com a distribuição do metal nos próprios biossólidos. Nestes casos, o Ni predominou nas frações mais fortemente retidas, conferindo ao metal comportamento distinto daquele observado pela adição do NiCl2. Tais diferenças puderam ser confirmadas pela ineficiência das equações obtidas nos experimentos com NiCl2, em predizer os teores do metal nas frações dos solos tratados com biossólidos. Na especiação, doses mais elevadas de calcário e turfa resultaram em menores teores de Ni solúvel e livre, os quais aumentaram com a dose de NiCl2. Concentração de ambas as formas de Ni se correlacionaram com os teores do metal absorvidos pelas plantas. Na aplicação de biossólidos ao PVAd, a determinação do Ni livre foi particularmente importante para se prever a biodisponibilidade de Ni para alface. Essencialmente, pode-se concluir que a extração seqüencial e a especiação em extrato de saturação foram eficientes para demonstrar diferenças do comportamento do níquel quando o metal foi aplicado como NiCl2 e como biossólido. / The role of Nickel in soils under the application of biossolids is still not very well known. The objectives of this study were to investigate the influence of total Nickel and organic carbon content, and soil pH, in the Nickel distribution among soil fractions and the bioavailability of the metal to lettuce. Three incubation pot trials were carried out in greenhouse placing in each one 3 kg of the 0-20cm layer of soil. Two soils types were considered: Typic Halpludult and Rhodic Kandiudox. In two of the trials, one for each soil type, soil samples were treated with rates of NiCl2, lime and peat as a source of organic matter and incubated during 120 days. In the third pot trial the above mentioned soils were incubated with four different types of biossolids during 150 days. Once the incubation period ended soils samples were collected and lettuce was planted in the pots of all three trials. Soils samples were submitted to a sequential extraction procedure which comprised the following fractions: exchangeable plus soluble; carbonate, organic, oxides and residual. Soil saturation extracts were also obtained for the determination of free Ni +2 concentration using the Donnan equilibrium technique. When NiCl2, peat, and lime were applied to soils, changes in pH due to lime caused exchangeable Ni to decrease and raised Ni content in organic and oxide fractions. Peat promoted an higher Ni content in the exchangeable fraction and reduced it in the oxide and organic fraction. I contrast NiCl2 raised Ni content in all of the above motioned fractions. Nickel content in all soil fractions were modeled by regression equations using total Ni, organic carbon, and pH as independent variables. Data for the Ni distribution in soils fractions under biossolids application were similar to results from sequential extraction in the biossolids in terms of percentage. In the biossolids trial Ni occurred most in residual fraction of soil, which contrasts with results obtained when Ni was supplied as NiCl2. Speciation study showed that higher rates of lime and peat promoted lower levels of soluble and free Ni in the soil solution. The opposite was detected when NiCl2 was applied. Both soluble Ni and free Ni +2 were well correlated with the Ni content in lettuce, when the metal salt was supplied as Ni source. However, free Ni +2 was a better indicator for Ni bioavailability when bissolids were applied in PVAd. In resume it may be concluded that the sequential extraction procedure and the speciation by means of the Donnan equilibrium approach were useful to express the different behavior of nickel in soil when NiCl2 or bissolids were the source of the metal.

No description available.