Alterações no teores de nutrientes em dois solos alagados, com e sem plantas de arroz Nutrients concentration changes in two flooded soils during the rice cycle

O alagamento e a presença de plantas alteram as propriedades biológicas e químicas do solo em relação ao ambiente anteriormente oxidado, influenciando a disponibilidade de nutrientes. Foi conduzido um experimento com o objetivo de avaliar as alterações dos teores de alguns nutrientes na solução de um Planossolo e um Gleissolo durante o ciclo do arroz. Os solos foram acondicionados em vasos (50 litros) contendo dispositivos para coleta da solução em diferentes profundidades, mantidos sem ou com plantas de arroz. A solução foi coletada aos 10, 19, 44, 77 e 113 dias de alagamento e determinados os teores de P, K, Ca, Mg, Fe e Mn. A concentração dos nutrientes na solução, especialmente o K, variou com a profundidade de coleta e com a presença de plantas, demonstrando a influência desses fatores na disponibilidade dos nutrientes em solos alagados.<br>Flooding a soil and growing plant on it can change its biological and chemistry properties, in comparison with a non-flooded environment. An experiment was conducted in order to study the nutrients dynamics in the solution of two soils (Planossolo and Gleissolo) during the rice cycle. Rice plants were cultivated in 50L containers having devices to collect soil solution at several depths (2.5, 5.0, 7.5 and 31cm). In the soil solution, with and without plant, P, K, Ca, Mg, Fe and Mn, were measured at 10, 19, 44, 77, and 113 days after the flooding. Potassium was especially sensible to the rice plant and depth of samplin

Distribuição e caracterização de substâncias húmicas em vermicompostos de origem animal e vegetal Distribution and characterization of humic substances in animal and plant vermicompost

A utilização de resíduos orgânicos, como fertilizantes e condicionadores de solo, requer sua maturação e monitoramento da qualidade do material resultante. A vermicompostagem é uma técnica que, ao longo do processo, elimina os potenciais efeitos adversos dos resíduos à saúde humana e ao solo. A avaliação das substâncias húmicas (SH) nos produtos finais quanto à quantidade e à qualidade permite inferir sobre o grau de estabilidade e maturidade dos vermicompostos. Este trabalho objetivou avaliar a qualidade de seis vermicompostos das seguintes matérias-primas: esterco bovino (EB), esterco ovino (EO), esterco suíno (ES), esterco de codorna (EC), borra de café (BC) e de erva-mate (BE) com respeito ao teor de ácidos húmicos (AH) e de ácidos fúlvicos (AF) e às suas características químicas, após 70 dias de compostagem. O fracionamento químico da matéria orgânica foi realizado com base na solubilidade em meio básico e ácido e a distribuição de cada fração calculada como percentual do C total. Foram calculados os índices de humificação: percentual de AH e razão AH/AF. Nos AH e AF purificados, determinaram-se a composição elementar (CHNO), a composição química por espectroscopia de infravermelho com transformada de Fourier (FTIR) e o índice de aromaticidade I1630/I2920. O teor de substâncias húmicas (AH+AF) decresceu na seqüência: BC > EO&#8776; BE&#8776; EB > ES > EC, tendo sua composição química também diferido entre os vermicompostos. O grau de maturidade foi superior nos vermicompostos de resíduos de origem vegetal (borra de café e de erva-mate). Os AH desses dois vermicompostos apresentaram menor proporção de grupos oxigenados e menor caráter aromático.<br>The use of organic residues as fertilizers and soil conditioners requires their maturation and the quality monitoring of the final product. Vermicomposting is a technique which, along with the composting process, eliminates the potential harmful effect of manure residues to human health and soil. The stability and maturity degrees of a given vermicompost are usually inferred from the quantity and quality of the humic substances in the resulting compost. This study aimed to evaluate the quality and maturity of vermicomposts from six different residues: cattle manure (CM), sheep manure (SM), pig manure (PM), quail manure (QM), coffee dregs (CD) and mate-tee dregs (MD), by determining the content of humic substances (humic, HA, and fulvic acids (FA) and their chemical composition, after 70 days of composting. The humic substances were chemically fractionated according to their solubility in basic and acidic medium. The distribution of total C in the different humic fractions was determined, and the humification indices HA percentage and HA/FA ratio were calculated. The elemental composition (CHNO) and chemical composition by infrared spectroscopy (IRSP) were determined in the purified HA and FA. An aromaticity index (I1(630)/I2920) was calculated based on the IRSP spectra. The vermicomposts differed in humic substance content (FA+HA), which decreased in the order CD > SM &#8776; MD &#8776; CM > PM > QM. The maturity degree was greater in the vermicomposts of vegetal residues (coffee and mate-tee dregs). The HA showed that the proportion of O containing functional groups and the aromatic degree were lowest in these two vermicomposts

Cation dynamics in soils with different salinity levels growing irrigated rice

Salinity levels in soils of the Outer Coastal Plain of Rio Grande do Sul, Brazil, can be high, due to excess of Na in the irrigation water, evapotranspiration and soil development from marine sediments. The cultivation of irrigated rice could be an alternative, since ion uptake as well as leaching by the establishment of a water layer could mitigate the effects of soil salinity. This study aimed to evaluate the dynamics of basic cations in the solution of Albaqualf soils with different salinity levels growing irrigated rice. The plow layer contained exchangeable Na percentages (ESP) of 5.6, 9.0, 21.2 and 32.7 %. The plant stand, dry matter, Na, K and Ca + Mg uptake at full flowering and grain yield were evaluated. The levels of Na, K, Ca + Mg and electrical conductivity (EC) in the soil solution were also measured weekly during the rice cycle at four soil depths, in the water layer and irrigation water. The Na, K and Ca + Mg uptake by rice at full flowering was used to estimate ion depletion from the layer under root influence. Soil salinity induced a reduction in the rice stand, especially in the soil with ESP of 32.7 %, resulting in lower cation uptake and very low yield at that site. As observed in the water layer and irrigation water, the Na, K, Ca + Mg and EC levels in the soil solution decreased with time at depths of 5, 10 and 20 cm, regardless of the original soil salinity, showing that cation dynamics in the plow layer was determined by leaching and root uptake, rather than by the effect of evapoconcentration of basic cations in the soil surface layer