Tales Tiecher

Forms of inorganic phosphorus in soil under different long term soil tillage systems and winter crops

O cultivo de plantas com diferentes habilidades de absorcao e utilizacao de P sob diferentes sistemas de preparo de solo por um longo periodo de tempo pode alterar a ciclagem e a distribuicao das formas de P inorgânico no solo, como resultado de maior ou menor eficiencia de utilizacao do P adicionado via fertilizantes. O objetivo deste trabalho foi avaliar o efeito de longo periodo de cultivo de diferentes especies de inverno sob diferentes sistemas de preparo de solo na distribuicao das formas de P inorgânico do solo. Em 1986, foi estabelecido o experimento com seis tratamentos de inverno (tremoco-azul, ervilhaca-peluda, aveia-preta, nabo forrageiro, trigo e pousio) implantados num Latossolo Vermelho aluminoferrico na regiao sudoeste do Parana, sob sistema plantio direto (SPD) e sistema de cultivo convencional (SCC). A adicao de fertilizantes fosfatados na linha de semeadura no SPD promoveu aumento de P inorgânico, nas formas labeis e moderadamente labeis, e o revolvimento do solo no SCC redistribuiu o P aplicado em profundidade, promovendo aumento no teor de P moderadamente labil no solo das camadas subsuperficiais. A aveia-preta e o tremoco-azul foram mais eficientes na ciclagem de P e, quando cultivados sob SPD, aumentaram o teor de P labil no solo das camadas superficiais.

Phosphorus accumulation and pollution potential in a hapludult fertilized with pig manure

Successive applications of pig litter to the soil surface can increase the phosphorus (P) content and alter its adsorption, promoting P transfer to surface or subsurface waters. The purpose of this study was to evaluate P accumulation and the pollution potential of a soil after application of pig litter. In March 2010, eight years after the installation of an experiment in Braco do Norte, Santa Catarina, SC, Brazil, on a Typic Hapludult, soil was sampled (layers 0-2.5, 2.5-5, 5-10, 10-15, 15-20 and 20-30 cm) after the following fertilization treatments: no pig litter fertilization, pig slurry application and pig manure application. In this period, 694 and 1,890 kg P2O5 ha-1 were applied in the treatments with pig slurry and pig manure, respectively. The P content was determined, based on Mehlich-1, anion exchange resin (AER), 0.01 mol L-1 CaCl2 and total P in the samples. The adsorption isotherm parameters were also determined by the Langmuir and Koski-Vahala & Hartikainem models in the layers 0-2.5 and 20-30 cm. The application of 1,890 kg P2O5 ha-1 in the form of pig manure led to P accumulation, as evidenced by Mehlich-1, down to a depth of 15 cm, by AER and 0.01 mol L-1 CaCl2 down to 20 cm and by total P to 30 cm. After application of 1,890 kg P2O5 ha-1 in the form of pig manure, the values of maximum P adsorption capacity were lowest in the deepest layer (20-30 cm), indicating the occupation of part of the adsorption sites of the particles. The application of swine manure to the soil over eight years increased the P quantity in the soil solution of the surface layer, indicating environmental contamination risk for surface and subsurface waters.

Iron oxides and organic matter on soil phosphorus availability

A continua expansao da producao agricola tem levado a uma crescente demanda de fertilizantes fosfatados. O conhecimento da dinâmica do fosforo no solo e suas interacoes com oxidos de ferro e materia orgânica podem ser uteis no desenvolvimento de estrategias eficientes para o manejo sustentavel, especialmente em um cenario de crescente escassez de fontes de minerais fosfatados. Nesta revisao bibliografica foi abordado a relacao do fosforo com oxidos de ferro e materia orgânica, e seu efeito na disponibilidade de fosforo. As culturas, normalmente, obtem fosfato de minerais intemperizados ou fertilizantes dissolvidos. No entanto, a quantidade de fosforo presente na solucao do solo depende das reacoes de adsorcao e dessorcao por oxidos de ferro, as quais podem ser influenciadas por interacoes com a materia orgânica. Portanto, os sistemas de recomendacao de fertilizantes com base em metodologias que consideram as interacoes entre componentes do solo, tais como oxidos e materia orgânica, e a capacidade de adsorcao de fosforo, resultantes de tais interacoes (por exemplo, analise de P remanescente), pode ser mais confiavel para garantir o uso eficiente e racional de fertilizantes fosfatados.

Combining visible-based-color parameters and geochemical tracers to improve sediment source discrimination and apportionment.

Parameter selection in fingerprinting studies are often time-consuming and costly because successful fingerprint properties are generally highly site-specific. Recently, spectroscopy has been applied to trace sediment origin as a rapid, less expensive, non-destructive and straightforward alternative. We show in this study the first attempt to combine both geochemical tracers and color parameters derived from the visible (VIS) spectrum in a single estimate of sediment source contribution. Moreover, we compared the discrimination power and source apportionment using VIS-based-color parameters and using the whole ultra-violet-visible (UV-VIS) spectrum in partial last square regression (PLSR) models. This study was carried out in a small (1.19 km(2)) rural catchment from southern Brazil. The sediment sources evaluated were crop fields, unpaved roads, and stream channels. Color parameters were only able to discriminate unpaved roads from the other sources, disabling its use to fingerprint sediment sources itself. Nonetheless, there was a great improvement in source discrimination combining geochemical tracers and color parameters. Unlike VIS-based-color parameters, the distances between sediment sources were always significantly different using the whole UV-VIS-spectrum. It indicates a loss of information and, consequently, loss of discriminating power when using VIS-based-color parameters instead of the whole UV-VIS spectrum. Overall, there was good agreement in source ascription obtained with geochemical tracers alone, geochemical tracers coupled with color parameters, and UV-VIS-PLSR models, and all of them indicate clearly that the main sediment source was the crop fields, corresponding to 57 ± 14, 48 ± 13, and 62 ± 18%, respectively. Prediction errors for UV-VIS-PLSR models (6.6 ± 1.1%) were very similar to those generated in a mixed linear model using geochemical tracers alone (6.4 ± 3.6%), but the combination of color parameters and geochemical tracers decreases the prediction error (5.4 ± 2.0%). Therefore, the use of VIS-based-color parameters combined to geochemical tracers can be a rapid and inexpensive way to improve source discrimination and precision of sediment source apportionment.

Effects of zinc addition to a copper-contaminated vineyard soil on sorption of Zn by soil and plant physiological responses.

The occurrence of high levels of Cu in vineyard soils is often the result of intensive use of fungicides for the preventive control of foliar diseases and can cause toxicity to plants. Nowadays many grape growers in Southern Brazil have replaced Cu-based with Zn-based products. The aim of the study was to evaluate whether the increase in Zn concentration in a soil with high Cu contents can interfere with the dynamics of these elements, and if this increase in Zn may cause toxicity to maize (Zea mays L.). Soil samples were collected in two areas, one in a vineyard with more than 30 years of cultivation and high concentration of Cu and the other on a natural grassland area adjacent to the vineyard. Different doses of Cu and Zn were added to the soil, and the adsorption isotherms were built following the Langmuirs model. In a second experiment, the vineyard soil was spiked with different Zn concentrations (0, 30, 60, 90, 180, and 270mg Zn kg(-1)) in 3kg pots where maize was grown in a greenhouse for 35 days. When Cu and Zn were added together, there was a reduction in the quantities adsorbed, especially for Zn. Zn addition decreased the total plant dry matter and specific leaf mass. Furthermore, with the increase in the activity of catalase, an activation of the antioxidant system was observed. However, the system was not sufficiently effective to reverse the stress levels imposed on soil, especially in plants grown in the highest doses of Zn. At doses higher than 90Znmgkg(-1) in the Cu-contaminated vineyard soil, maize plants were no longer able to activate the protection mechanism and suffered from metal stress, resulting in suppressed dry matter yields due to impaired functioning of the photosynthetic apparatus and changes in the enzymatic activity of plants. Replacement of Cu- by Zn-based fungicides to avoid Cu toxicity has resulted in soil vineyards contaminated with these metals and damaging of plant photosynthetic apparatus and enzyme activity.

Contribuição das fontes de sedimentos em uma bacia hidrográfica agrícola sob plantio direto

Knowledge of the main diffuse sources of sediment production can enhance efficiency in use of public resources invested in management strategies that seek to mitigate sediment transfer to waterways from catchment areas. The aim of the present study was to evaluate the sediment sources in a rural catchment with predominance of annual crops under a no-tillage system and with intense and inappropriate exploitation of natural resources (soil and water) by quantifying the relative contribution of roads and croplands in the overall production of sediments. Inappropriate exploitation is a result of a lack of planning of crop production areas and access pathways, both from the point of view of their location in the landscape, and of management practices which are incompatible with the conditions of soil fragility and relief. The catchment is located in the municipality of Julio de Castilhos, State of Rio Grande do Sul. The period under study was from May 2009 to April 2011. For identification of the sources we used the fingerprinting method, which compares the soils from different sources and the sediments in suspension in the drainage canal using tracer elements. Inadequate soil management in croplands, the lack of planning of access roads, and the absence of control practices for surface runoff compatible with the fragility brought about by the soil and topography of the watershed have caused the emergence of accelerated erosion with negative effects for the farmer and society. Roads represent a high percentage of contribution to sediment transfer, but the contribution of cropland increases with rainfall of high magnitude. This shows that the magnitude of rainfall events affects the proportion of contribution among sources throughout the year in the catchment area, affecting the process of mobilization of sediments and nutrients towards the drainage system.

Phosphorus fractions in sandy soils of vineyards in southern Brazil

As aplicacoes de fosforo (P) em vinhedos podem causar o acumulo desse nutriente no solo e maximizar seu potencial poluente. Este trabalho objetivou quantificar as fracoes de acumulacao de P em solos arenosos cultivados com videiras na regiao Sul do Brasil. Para isso, amostras de solo foram coletadas nas camadas de 0-5, 6-10 e 11-20 cm em uma area de campo nativo e em dois vinhedos: um com 14 anos de cultivo (vinhedo 1) e outro com 30 anos (vinhedo 2), localizados no municipio de Santana do Livramento, Rio Grande do Sul (RS), Brasil. As amostras foram secas, moidas e submetidas ao fracionamento quimico de P. Os resultados evidenciaram que os teores de P inorgânico aumentaram ate 20 cm de profundidade, principalmente no vinhedo 2, em especial nas fracoes labeis extraidas por resina de troca anionica e por NaHCO3, na fracao moderadamente labil, extraida por NaOH 0,1 e 0,5 mol L-1, e na fracao nao labil, extraida por HCl 1 mol L-1, representando potencial de eutroficacao das aguas. As aplicacoes de fertilizantes fosfatados na adubacao de correcao e de manutencao nos vinhedos com maior tempo de cultivo aumentaram os teores de P na fracao orgânica extraida por NaHCO3 na camada de 0-5 cm, e na fracao moderadamente labil extraida por NaOH 0,1 mol L-1, ate 20 cm de profundidade.

Identificação de fontes de produção de sedimentos em uma bacia hidrográfica de encosta

O uso do solo fora de sua aptidao agricola e o que norteia a degradacao dos recursos naturais por meio das atividades antropicas. As atividades agropecuarias estao entre as que mais perturbam o meio ambiente, expondo o solo a acao dos processos erosivos e acelerando a transferencia de sedimentos aos corpos de agua. Nos ultimos anos, o metodo fingerprinting para identificacao de fontes de sedimentos tem sido utilizado com sucesso no mundo, porem, trabalhos dessa natureza realizados no Brasil ainda estao em carater incipiente. O objetivo deste trabalho foi estimar a proporcao de contribuicao das principais fontes de producao de sedimentos de uma bacia hidrografica de encosta, onde predominam solos rasos e agricultura menos intensiva no sistema familiar. Essa bacia esta localizada na regiao central do Estado do Rio Grande do Sul, tendo por ocupacao do solo predominante areas de floresta nativa seguida das de campo nativo, capoeira, lavouras anuais e, em menor expressao, silvicultura (eucalipto) e area urbanizada. Para a identificacao das fontes, foi utilizado o metodo fingerprinting, que compara os solos de diferentes fontes, e os sedimentos, que sao encontrados em suspensao no canal de drenagem, usando elementos tracadores. As maiores contribuicoes na producao de sedimentos sao provenientes da erosao superficial do solo. Para o primeiro periodo de monitoramento, foi identificada uma producao relativa de sedimentos de 60 % das estradas, para o ponto T2; de 100 % da malha, para o T3; e de 77 % da malha, para o T4. Para o segundo periodo de monitoramento, as estradas contribuiram relativamente com 81 % do sedimento em suspensao no ponto T2 e com 76 %, no T3. Ja no ponto T4, a maior contribuicao foi da malha com 82 %. O metodo se apresentou sensivel em detectar mudancas na contribuicao de cada fonte em razao das caracteristicas apresentadas por cada uma delas, para o tipo de bacia hidrografica estudada.

FÓSFORO MICROBIANO EM SOLOS SOB PASTAGEM NATURAL SUBMETIDA À QUEIMA E PASTEJO

In natural grassland ecosystems deficient in available P, the temporary immobilization of P in microbial biomass and its subsequent mineralization can be considered a potential mechanism of P supply to plants. The purpose of this study was to evaluate the influence of burning and grazing of grassland vegetation on the dynamics of soil P, with emphasis on the content of P immobilized in microbial biomass. The treatments consisted of the combination of grazing (presence or absence) and burning (presence or absence) in a natural grassland on slope and lowlands after 13 years under a management involving burning and grazing. Burning and grazing were arranged in a completely randomized design with four replications. Soil samples were collected from the 0-10 cm layer twice during the growing period of native pasture, always immediately after grazing. The stocking rate was calculated based on a utilization rate of 20-35 % of existing forage mass. The P content stored in the soil microbial biomass, the total P content and total organic P in soil were determined. The statistical analysis was based on analysis of variance by randomization tests. The microbial P content of natural pasture ranged from 11.4 to 57.3 mg kg-1, representing on average 38 and 32 % of total organic P in soil in the first and second evaluation, respectively. The P immobilized in microbial biomass is a potential reserve of P that can meet the demand for native species in natural pastures, and is a more sensitive indicator than the total organic P content of the soil to detect changes induced by grazing. Management of natural pastures with fire decreases the amplitude of the increase in microbial P due to grazing.

Accumulation of phosphorus fractions and contamination potential in vineyard soils in the southern region of the state of Santa Catarina, Brazil

In vineyards, if phosphate is applied both before planting and at intervals during growth without consideration of technical criteria, the soil P fractions may be increased and their proportions altered. This study was carried out to evaluate the accumulation of P fractions and the parameters of the adsorption isotherm in a sandy Typic Hapludalf soil in vineyards with a history of successive and excessive phosphate fertilization. In December 2010, two vineyards were selected, one 4 and the other 15 years old, in Urussanga, State of Santa Catarina (Brazil). Three trenches were dug in each area and soil was collected from the 0-5, 5-10 and 10-20 cm depth ranges. The soil samples were dried in a forced-air oven, sieved and subjected to chemical analyses, P chemical fractionation and P adsorption isotherms. Excessive phosphate fertilization, before and during cultivation, particularly in the older vineyard and, consequently, with a longer history of phosphate fertilization, increased the inorganic P concentrations to the depth of 20 cm, especially in labile fractions extracted by anion exchange resin and NaHCO3 in the non-labile fraction, as well as in the non-labile fraction extracted by 1.0 mol L-1 HCl. The application of phosphate fertilizers and the long cultivation period increased the P levels in the organic labile fraction extracted by 0.5 mol L-1 NaHCO3, and especially in the moderately labile fraction extracted by 0.1 and 0.5 mol L-1 NaOH. Phosphate fertilization of older vineyards, i.e., cultivated for 15 years, increased the amounts of P desorbed in water, indicating a risk of contamination of surface waters and groundwater. The phosphate fertilization before planting, without considering the results of soil analysis, and during cultivation, disregarding the results of soil analysis, leaf analysis and expected yield, led to a reduction in the maximum P adsorption capacity in the 0-5 cm layer of vineyard 2, indicating saturation of part of the reactive particle adsorption sites.