ABSTRACT
Phosphorus is one of the most abundant chemical elements but has a low bioavailability index. Therefore, microrganisms play a fundamental role in providing insoluble phosphorus to plants. The objective of this study was to evaluate the capacity of bacteria to solubilize inorganic phosphates in soils with different fertilization histories. Soil and rhizosphere samples were collected from a Red Distroferric Latosol, including a control without mineral or organic fertilizer (C), treatment with mineral fertilizer (MF) according to the needs of each crop, and treatment with organic fertilizer [300 m3 ha-1 of swine wastewater (SW)]. The medium containing calcium phytate presented more colony-forming units (CFU) for all fertilization histories, and growth in treatments C and MF was 50% higher than treatment with SW. CFU values in soils treated with SW were lower than those in the other treatments, and the diversity of insoluble phosphate-solubilizing bacteria (PSB) was higher in treatment C. These results indicate a negative relationship between phosphorus concentrations and the number of PSB.
O fósforo é um dos elementos químicos mais abundantes, mas tem um baixo índice de biodisponibilidade. Portanto, micro-organismos desempenham um papel fundamental no fornecimento de fósforo insolúvel para as plantas. O objetivo deste trabalho é avaliar a capacidade das bactérias em solubilizar fosfatos inorgânicos em solos com diferentes históricos de fertilização. Amostras de solo e rizosfera foram coletadas de um Latossolo Vermelho Distroférrico, incluindo controle sem adubação mineral ou orgânica (C), tratamento com adubação mineral (MF) de acordo com as necessidades de cada cultura e tratamento com adubação orgânica [300 m3 ha-1 de águas residuárias da suinocultura (SW)]. O meio contendo fitato de cálcio apresentou mais unidades formadoras de colônias (UFC) para todas as histórias de fertilização, e o crescimento nos tratamentos C e MF foi 50% maior que o tratamento com SW. Os valores de CFU nos solos tratados com SW foram menores que nos demais tratamentos, e a diversidade de bactérias insolúveis solubilizadoras de fosfato (PSB) foi maior no tratamento C. Esses resultados indicam uma relação negativa entre as concentrações de fósforo e o número de PSB.
Subject(s)
Phosphorus , Plants , Soil , BacteriaABSTRACT
ABSTRACT: The use of wastewater in agriculture has been practiced on an increasing scale over the past decades because of its fertilizing potential and the reduction in demand for surface water and groundwater. However, this practice may bring harm when performed without planning, not respecting the capacity of the soil to recycle organic waste. The most common problems are contamination of surface and groundwater via leaching and runoff, as well as accumulation of nutrients and potentially polluting elements that compromise chemical, physical and biological characteristics of the soil. The biological compartment, represented by the micro, meso and macrofauna, plays an important role in nutrient cycling, decomposition of organic matter, particle movement and transport of materials at different depths, helping to maintain soil physical and chemical characteristics. In this sense, this paper aims to discuss the effect of using different kinds of wastewater in agriculture on soil biology, highlighting strengths and weaknesses, as well as emphasizing the need to conduct investigations that enhance the positive aspects of wastewater use associated with edaphic processes.
RESUMO: O uso de efluentes na agricultura vem sendo praticado em escala crescente ao longo das últimas décadas em virtude de seu potencial fertilizante e da redução na demanda de águas superficiais e subterrâneas. No entanto, tal prática pode trazer prejuízos quando realizada sem planejamento, não respeitando a capacidade de suporte do solo para a reciclagem de resíduos orgânicos. Os problemas mais comuns são a contaminação de águas superficiais e subterrâneas, via lixiviação e escoamento superficial, bem como o acúmulo de nutrientes e elementos potencialmente poluentes que comprometem as características químicas, físicas e biológicas do solo. O compartimento biológico, representado pela micro, meso e macrofauna, desempenha importante papel na ciclagem de nutrientes, decomposição da matéria orgânica, movimentação das partículas e transporte de materiais em diferentes profundidades, contribuindo para a manutenção das características físicas e químicas do solo. Nesse sentido, o presente trabalho tem por objetivo discutir o efeito do uso de diferentes efluentes na agricultura sobre a biologia do solo, destacando aspectos positivos e negativos, bem como enfatizar a necessidade de conduzir investigações que potencializem os aspectos positivos do uso de efluentes associados aos processos edáficos.
ABSTRACT
This study aimed at evaluating the effects of pig slurry application with mineral fertilizer on ions leaching from the soil in soybean crop. The experiment was carried out in 24 drainage lysimeters under protection. The soybean cultivar CD 202/COODETEC was sown in a soil that received 0, 100, 200 and 300 m³ha-1of pig slurry in one cycle, with or without mineral fertilizer. There were three samplings of soil throughout the trial to determine the pH, N, NO3-, K+, Ca2+, Mg2+, Na+, Cu+2, Zn+2, OM, CEC, EC and SAR six times during the crop cycle. The yield was determined in the plants. In soil, pig slurry increased the concentrations of pH, NO3-, K+, Zn+2, OM and CEC, while mineral fertilizer increased P and Zn+2concentrations. The limits observed for the leachate parameters did not present environmental problems according to the Brazilian legislation, but in the intermediate and long term, there special attention should be given to NO3-, P, Na+, EC and SAR. Soybean yield was higher with mineral fertilizer and increased with pig slurry application.
ABSTRACT
The objective of this work was to evaluate the environmental effects of the use of pig slurry to irrigate the corn crop grown in a typical Red Distroferric Latosol and in leachate composition. Twenty four lysimeters, filled with soil, in a protected environment, received five doses of pig slurry (0; 112.5; 225; 337.5 and 450 m³ ha-1 per growing cycle) combined with two mineral fertilization doses (50 and 75% of the recommended dose - 80 kg ha-1of nitrogen). Corn height and yield were evaluated, as well as nutrients in the soil and in leachate. From the results obtained in the first year of experiment, it was concluded that the concentrations of nitrate increased by increase of pig slurry application, and thus, it would be necessary to develop further studies in medium and long term.